12 volt power efficiency.....

[feral]

I am looking at installing a dual battery setup in the back of my D2. At this stage I am not sure if the auxillary battery will be permanently mounted or used in a battery box.

The general way that most people do is to use a dual battery controller which will charge the aux. battery. All this is wired using the proper specifications of wiring and fuse, circuit breakers, etc.


There is another way which is beginning to be more prevalent in the caravan industry.

The plan is to use an inverter and a battery charger to charge the aux. battery. Of course this will be wired correctly using proper fuses, circuit breakers, etc. For those who are concerned about 240v being introduced into the vehicle, the position of the inverter and battery charger will be protected by the left storage bin. I will have a spark/high voltage label clearly displayed to protect other users.


Now the theory that decides which way to go is that with the dual battery controller is that it only begins to charge the aux. battery AFTER it charges the mains. When it does this it will only charge as efficiently as the alternator can deliver so if the aux. battery does not receive 13.8v it will not be charging.

With the inverter and battery charger system, the inverter will work even though the voltage may drop to 12 volts. This in turn runs the battery charger which delivers 13.8v or more to the aux. battery. The inverter and battery charger are all protected by their onboard protection systems and will automatically shut down if any issues arise.

Its all to do with the 'state of charge' of the battery. If the aux. battery is fully charged it will run longer.

Will it work ? :angel:

Is there anything I have missed ? ;)

I have read so much info on the whole deal...its information overload :confused:

[jik22]

Not professing to be an expert in this...but....if the alternator isn't delivering enough voltage to charge the battery you have a problem. Also, in a 4x4, surely you'd want to ensure the starting battery was charged before you started charging the aux, wouldn't you? Even if you didn't, most battery controllers have an override so you can immediately start charging both.

You're never going to get a 100% full charge to any battery anyway, but without the expensive smart chargers I've been looking at recently, I think this is true of any battery charger, whether alternator or a 240v one.

[Bushie]

If your aux battery is being discharged by whatever you have plugged into it then the charger will be trying to top it up all the time, what is the chance of this dragging your main battery down below the voltage required for starting. Can you set up some device to shut it down when voltage gets to the critical level.


Martyn

[WildOne]

If your aux battery is being discharged by whatever you have plugged into it then the charger will be trying to top it up all the time, what is the chance of this dragging your main battery down below the voltage required for starting. Can you set up some device to shut it down when voltage gets to the critical level.


Martyn

You could wire the supply to the inverter through a relay activated by your ignition. Still undecided as to the benefits of going the inverter way as opposed to a normal dual battery setup.

[beforethevision]

I am looking at installing a dual battery setup in the back of my D2. At this stage I am not sure if the auxillary battery will be permanently mounted or used in a battery box.

The general way that most people do is to use a dual battery controller which will charge the aux. battery. All this is wired using the proper specifications of wiring and fuse, circuit breakers, etc.


There is another way which is beginning to be more prevalent in the caravan industry.

The plan is to use an inverter and a battery charger to charge the aux. battery. Of course this will be wired correctly using proper fuses, circuit breakers, etc. For those who are concerned about 240v being introduced into the vehicle, the position of the inverter and battery charger will be protected by the left storage bin. I will have a spark/high voltage label clearly displayed to protect other users.


Now the theory that decides which way to go is that with the dual battery controller is that it only begins to charge the aux. battery AFTER it charges the mains. When it does this it will only charge as efficiently as the alternator can deliver so if the aux. battery does not receive 13.8v it will not be charging.

With the inverter and battery charger system, the inverter will work even though the voltage may drop to 12 volts. This in turn runs the battery charger which delivers 13.8v or more to the aux. battery. The inverter and battery charger are all protected by their onboard protection systems and will automatically shut down if any issues arise.

Its all to do with the 'state of charge' of the battery. If the aux. battery is fully charged it will run longer.

Will it work ? :angel:

Is there anything I have missed ? ;)

I have read so much info on the whole deal...its information overload :confused:

I think perhaps you are thinking waaay too deep. Its got some serious losses doing such a conversion. perhaps 30% depending on quality. To top up the main battery will only take like 30 secs, in most cases, to replace the starting losses. Assuming it starts the second battery above like 13.5V or whatever, my FL atleast would link them up instantly after starting. I would be only using the charger theory you mentioned if you wanted to charge the secondary off a screwed main, but thats not real bright or useful. Stick with a dual battery controller and be happy in its reliability.

An alternator at decent rpm is like half a dozen decent battery chargers running together.

IMHO atleast.

Cheers!

[awabbit6]

With the inverter and battery charger system, the inverter will work even though the voltage may drop to 12 volts. This in turn runs the battery charger which delivers 13.8v or more to the aux. battery.


If the main voltage supply drops to 12V you have a problem and the last thing you should be worrying about is charging an auxillary battery.
I really don't see how this is a beneficial system. You are converting 12VDC to 240VAC and back to 12VDC. With heat losses at every conversion, you will be wasting alot of power. Why convert to 240V??
A conventional dual battery setup works well and is far less complicated than the system you are describing.
I think that the advantage in a caravan is so that the battery can be charged while on a powered caravan site.

[WildOne]

If the main voltage supply drops to 12V you have a problem and the last thing you should be worrying about is charging an auxillary battery.
I really don't see how this is a beneficial system. You are converting 12VDC to 240VAC and back to 12VDC. With heat losses at every conversion, you will be wasting alot of power. Why convert to 240V??
A conventional dual battery setup works well and is far less complicated than the system you are describing.
I think that the advantage in a caravan is so that the battery can be charged while on a powered caravan site.

Have to agree,
add to that the cost of a decent inverter+decent battery+wiring etc. Would work out more than a proven basic and reliable dual battery setup

[drivesafe]

Sorry for how abrupt this is but there is no polite way to address the suggestion of driving around with live 240 VAC in a vehicle, especially a 4x4 it is nothing short of lunacy.

Besides the fact that it is totally unnecessary as any alternator can easily charge two batteries at the same time and contrary to all the BS, they can be FULLY charged by the alternator, IF everything is set up properly in the first place.

The situation of having ordinary vehicles ( Tour Buses have 240 VAC on board but there are major differences between them and normal vehicles ) is getting more and more attention for different emergency services departments and I would not be too surprised if it is not made illegal before too long.

For less than the cost of a battery charger or an inverter ( let alone the combined cost ) you can buy a third battery and your alternator can not only charge them both but can do it quicker than an inverter/battery charger set up can, plus you end up with twice as much stored power.

Sorry Feral, it just can’t be made 100% safe and as there is no legitimate reason for doing it in the first place, why do it at all.

[Dunnie]

I agree with the above comments. I can recommend Smart Solenoids from the USA retailed by ARB. We've used many of these on boats and crane-equipped vehicles at work as well as one each on my two personal Land Rovers. Never had the slightest problem with charging big dual battery setups and they give you emergency starting as well. The only better system that you could install would be a marine battery management system such as those made by Adverc, but I think that this sort of thing would be over the top for an auto installation. The problems that modern ambulances have with their huge dual alternators is that they fry the Hell out of the batteries. You can have too much of a good thing.

[feral]

OK, this is all good but I am not convinced either way yet :D

This is now going to get very technical and very messy and we still wont be any better for it but here goes to address some of your concerns.

The inverter does not need a constant high voltage to work. It will generate power wether it is at 11v or 14v. It has a low voltage cut out so it will shut down the draw from your main battery at its setting or if that is too low, you can purchase other cut outs. This will protect the main battery.

With the dual battery setup once the engine is stopped, so has your charging ability. With the inverter it will keep charging until it reaches the low volt cut out. If thats an hour longer or whatever is yet to be determined.

The inverter and battery charger all have there own protection systems. This means that they are all fused, circuit breakers or whatever internally. If the event of a problem they will shut down. This would happen if I use these in the van or even at home. They are safe to use in the shed but are not safe to use in a vehicle??? Thousands of campers have inverters!
You could even wire it up to have the inverter active only when the engine of the vehicle is running, but this then knocks out the advantage of charging when the vehicle is not used.

The whole system would be protected by circuit breakers the same as the dual battery setup so this would protect the vehicle so there is no issue here really.

What I am looking at is the efficiency of charging a seriously depleted battery.

I have read too many reports of people with flat or stuffed aux. batteries because they do not get enough charge into them quickly. I have read reports of having to drive hours just so they can recharge the battery and who wants to do that. If I can recharge the aux. battery in 2 hours instead of 5, isn't this better?

Like I said it is to do with the state of charge. I have yet to find some actually statistics in relation to hypothetical situations where say your battery is down to 50% capacity, how long would it take to bring it back to 100% or its maximum using the alternator or even a charger. Its all open to speculation and heresay.

From the 'BS' info that I have seen it appears that because of the specifications of the battery charger wether it be 2, 3 or 4 stage charging it charges the aux. battery quicker than the alternator.

Maybe I am expecting too much in an imperfect world :wasntme:

Cheers.

[Captain_Rightfoot]

Well, I'm not sure I understand what the issues are here. However I just installed a second battery and one of drivesafes systems. We just had a 5 week trip, with our fridge and camping gear running off the aux. The beauty of this system is I didn't think about it for 5 weeks... it just worked. How good is that. :)

[Bradtot]

Hello Lyndon just to add my 10cents
I use one of Drivesafes sc40 charger systems but instead of the output going directly to the aux battery I have it connected to a dc dc convertor... 8-12v in 13.8v out at 20 amps. When the main starting battery falls below its presets it cuts off the dc dc charger but the starter battery allows me to start the Rangie.
Like you I wanted a faster charge to the aux battery and this way does it.
It will continue to charge when I have turned ign off until the starter battery voltage has dropped enough to disconnect the sc40 therefore disconnecting the charge. This works for me and I have had it like this for over 2 years.
My only problem is the aux battery is deep cycle semi calcium and still does take a long time to recharge when flat.
Brad:eek:

[scrambler]

I guess it all depends on what you want to achieve.

The energy output (volts x amps) of the alternator is fixed (for any given situation), therefore any losses in heat etc mean something, somewhere is losing out. Inverter (losses) to charger (losses) to battery will mean there is reduced charging efficiencies, which might affect the rate of charge of the starter, auxillary or both.

Brad's system is set up to hold more charge in the aux than is usual, but reads to me like it would preferentially charge the starter battery while on the move, then move charge across to the aux when stationary, maintaining 12 volts minimum in the starter. Did I read this right, Brad?

A system that directs current, rather than converting it to AC and back to DC (or even DC-DC) will be more efficient overall (i.e. faster charging both batteries to full) but it all depends on what you want/need to achieve.

[Bradtot]

Brad's system is set up to hold more charge in the aux than is usual, but reads to me like it would preferentially charge the starter battery while on the move, then move charge across to the aux when stationary, maintaining 12 volts minimum in the starter. Did I read this right, Brad?


Yes correct
Brad

[awabbit6]

With the dual battery setup once the engine is stopped, so has your charging ability. With the inverter it will keep charging until it reaches the low volt cut out. If thats an hour longer or whatever is yet to be determined.

If I understand this correctly, you want to be able to charge one battery from another. Is that correct? If so, why?
In terms of the total energy stored, you will actually be worse off after charging because some energy will be converted to heat during the charging process. From what I can find, chargers are around 80% effiecient. That means that there is a 20% loss as heat!



From the 'BS' info that I have seen it appears that because of the specifications of the battery charger wether it be 2, 3 or 4 stage charging it charges the aux. battery quicker than the alternator.

Depending on how clever the charger is, that may be so. It is only the fact that charging is controlled in a multistage charger. In terms of brute charging ability, an alternater should be just as effective. How fast do you need to charge the battery?

I feel that I am missing something here. Whether I am or not, the inverter still seems unecessary. (not to mention the potential hazard suggested by drivesafe)

[Andrew]

Why why why ?


Why would you want to do this? Have you considered the extra heat generated, the safety issues, the aditional space required, and the expense?

If you want to do it obviously you'll do it , but it just sounds stupid.

[Andrew]

To add to my previous post
Caravans use this system, so that they can use 240v appliances (USING AN INVERTER)from there batteries and a charger to charge the batteries, when plugged into 240v. Caravans dont just do it for the sake of doing it.

[jx2mad]

What you have to remember is that to recharge any flat or low battery you have to replace the same quantity of power taken out. For example , if you have a battery capable of supplying 100 amps/hour and you flatten it. you have to replace the same amount used. Say you run an appliance that draws 20a/h. then the battery would be flat in 4 hours. To recharge using a battery charger supplying say 5a/h would take 20 hrs. If you used an inverter on your main battery to drive your charger, how long do you think your main battery would last? 20h? I think not. I run dual batteries in my defender and on occasions I have forgotten to turn off my fridge at night. So the aux battery is rather low the next morning. However after a few kms the battery charge has been replenished from the alternator no problems. Jim

[Bush65]

OK, this is all good but I am not convinced either way yet :D

This is now going to get very technical and very messy and we still wont be any better for it but here goes to address some of your concerns.

The inverter does not need a constant high voltage to work. It will generate power wether it is at 11v or 14v. It has a low voltage cut out so it will shut down the draw from your main battery at its setting or if that is too low, you can purchase other cut outs. This will protect the main battery.

With the dual battery setup once the engine is stopped, so has your charging ability. With the inverter it will keep charging until it reaches the low volt cut out. If thats an hour longer or whatever is yet to be determined.

The inverter and battery charger all have there own protection systems. This means that they are all fused, circuit breakers or whatever internally. If the event of a problem they will shut down. This would happen if I use these in the van or even at home. They are safe to use in the shed but are not safe to use in a vehicle??? Thousands of campers have inverters!
You could even wire it up to have the inverter active only when the engine of the vehicle is running, but this then knocks out the advantage of charging when the vehicle is not used.

The whole system would be protected by circuit breakers the same as the dual battery setup so this would protect the vehicle so there is no issue here really.

What I am looking at is the efficiency of charging a seriously depleted battery.

I have read too many reports of people with flat or stuffed aux. batteries because they do not get enough charge into them quickly. I have read reports of having to drive hours just so they can recharge the battery and who wants to do that. If I can recharge the aux. battery in 2 hours instead of 5, isn't this better?

Like I said it is to do with the state of charge. I have yet to find some actually statistics in relation to hypothetical situations where say your battery is down to 50% capacity, how long would it take to bring it back to 100% or its maximum using the alternator or even a charger. Its all open to speculation and heresay.

From the 'BS' info that I have seen it appears that because of the specifications of the battery charger wether it be 2, 3 or 4 stage charging it charges the aux. battery quicker than the alternator.

Maybe I am expecting too much in an imperfect world :wasntme:

Cheers.
You haven't been convinced of the yet, despite the good advice!

Inverters and chargers are not very efficient. Yet you want to use them to charge an aux battery from your starting battery!

So whatever energy you can take from the starter battery, without drawing it down too low, is deminished by the considerable losses in both the inverter and the charger.

Now compare this to the SC40 dual battery unit that Drivesafe makes.

When both the aux and starter batteries are charged and the engine is stopped. The SC40 connects both batteries together and allows you fridge camp lights etc to draw power from both batteries. When the voltage of the starter battery drops to a set value that will still allow the engine to be started, the SC40 disconnects the aux battery from the starter and you can continue to run the fridge until the aux battery is flat. If you get a second SC40, it can be installed so the fridge will not draw the aux battery down so low that it becomes stuffed.

When the engine is stopped, this will give you more hours for running your fridge from the 2 batteries than using the inverter and charger. It will cost much less and will be safer.

[drivesafe]

Hi again Feral, you have a few things a tad wrong and I’ll just follow on from all those who have posted above.

For a starter, to be able to charge a battery quicker than the alternator can, you need a battery charger with at least a 20 amp capacity, even with an 80% efficiency rate, this means you need 25 amps to be drawn off the main battery.

Now this does not yet covered both the size and efficiency losses of your inverter and as the VERY BEST inverters are 93% efficient, your still looking at at least 30 amps being pulled from your Cranking battery. How long do you think your cranking battery can both supply that sort of current for and how often do you thing it can do that before you need a new battery.

It’s all self defeating.

I have posted in a number of other threads how you can use a SMALL inverter and a SMALL battery charger to top off you auxiliary battery WHILE YOU ARE CAMPED, someone might know the thread and post a link to it but as far as getting more stored capacity goes, you are far, FAR better off just fitting a second auxiliary battery then to use the inverter/battery charger.

With 2 auxiliary batteries, your alternator will easily replace the amount of amps used by the two batteries quicker than even a 20 amp charger could ever hope to do.

Add to this the cost difference, a charger and an inverter of this size would run to at least $500 to $600 and we haven’t covered the cost of heavy cable, about $100, which will be necessary if you want to stop the efficiency of your set up getting any worse.

Then there is some form of battery protection to stop over discharging the cranking battery, another $100.

Your now looking at around $800 for a basic set up that will, in your mine, allow you to charge your, say, 100 A/H auxiliary battery quicker that the alternator will.

This will mean that you will have about 100 A/Hs of total power available, taking into account that you take you 100 A/H battery down to 25% SoC and you add 25 A/H buy pulling 35 amps from your cranking battery.

For about $500 you could add the heavy cable, another 100 A/H battery and if you installed an SC80, you would have a total available capacity 135 A/Hs. This is based taking the auxiliary batteries down to only 50% Soc and the 35 amps from the equivalent of a 70 A/H cranking battery, is available as 35 amps at the auxiliary batteries.

Now if you were to take the auxiliary batteries down to 25% SoC the you are now looking at around 185 A/Hs.

That’s nearly double the power for just over half the price and based on a dollar to dollar comparison, that’s well over a 100% improvement over the inverter/battery charger set up.

And all this extra power without risking electrocuting anyone.

Just something to thing about.

[DiscoStew]

I have just had an SC80 installed as I have an Aux in the car and a trailer battery. This will control the recharging of all batteries while on the go. Many thanks to Drivesafe for his patience with my many questions.

However I do intend to use the inverter-to-recharger option to top up the trailer battery from the AUX battery while set up in camp. This was based on advice from drivesafe in the other thread and assumes that daily driving will keep the Aux battery close to fully charged so you might as well use it at night to top up the trailer. http://www.aulro.com/afvb/showthread.php't=37661&highlight=inverter

However I am finding that the Expensive 10A recharger is not performing nearly as well from the 600w Modified Sine Wave inverter as it does from a mains suppy. In fact it makes a clicking sound every 2 secs approx and makes me nervous that I am damaging it. Plus it takes a long time to start putting out >13.5Amps. Any comments on these symptoms would be appreciated.

Note that the Supercheap 10A recharger seems to work fine, gets to 13.5v quickly.

If this is typical then I don't think it meets the objective for charging fasting (which was dubious anyway according to previous posts).

[jik22]

However I am finding that the Expensive 10A recharger is not performing nearly as well from the 600w Modified Sine Wave inverter as it does from a mains suppy.

What smart charger are you using? I want one for the garage (Or running from a generator) to fully charge my batteries or keep them topped up between periods of use.

[DiscoStew]

What smart charger are you using? I want one for the garage (Or running from a generator) to fully charge my batteries or keep them topped up between periods of use.

Federal PureCharge10 Intelligent 3-Stage Charger. Bought it from Battery World for approx $200 I think. Normally works very well from mains but does not work well from an inverter. It took about an hour to get up to 13.5v and both it and the inverter sounded like they were struggling. Perhaps it needs PureSine.

The SuperCheap one is a Callibre Two Stage Charger which will put out about 13.8v from mains and 13.5 from the inverter, which is enough to recharge albiet slowly. And for the application I described above it will have all night just to top up about 20amphours from the day's use, so slow is not a problem.



I have posted in a number of other threads how you can use a SMALL inverter and a SMALL battery charger to top off you auxiliary battery WHILE YOU ARE CAMPED.

Given the words SMALL are uppercase, that may be the key to the problems I am having. Maybe the cheaper one is better for a reason but my web searches are yet to turn up an answer.

[jik22]

Federal PureCharge10 Intelligent 3-Stage Charger. Bought it from Battery World for approx $200 I think.

Thanks. Looks like I'll have to go to a store and have a look as their website is hopeless.

[Quiggers]

Got a genuine question for drivesafe:

What's your opinion of these emergency start packs?

I'm sure you know, Mat, and I've seen them in various junkmail catalogues, usually bright yelloy or red, with short jumper type leads etc, for $100 or less...worth the $, or forget it?

Cheers, GQ

[feral]

Here are some specifications of the system that I was thinking of installing.

Jaycar 150w Modified Sine Wave $100
or
Jaycar 300w Sine Wave $200.

Jaycar 4 stage 16 amp battery charger $169.

So it was something to think about for a while :wallbash:

Cheers.

[bris_faz]

sorry feral but i tend to agree with the above comments. you talk about efficient charging of your aux, but the process of inverting and then regulating the power back to 12v is highly inefficient.

try looking at a dual battery system with a voltage sensor in it (it will charge your aux after and only after your main is back up to speed). they are available with a switch to safely jump start your main off the aux battery if your main does get to low to start.

I would be putting one of these on a glass matt/gel cel deep cycle battery. these batteries prefer to be charged/discharged slowly, they wont spill, and are sealed so you can place them inside the cab if you want.

The bottom line for me is that i would rather have warm beer in my fridge than be stuck in the middle of nowhere because i cant start my motor.

I hope this has helped.

(p.s. nothin stopping you putting a battery charger in your recovery pack for when your close to a 240v outlet eg caravn park etc.)

[chosen]

Just a thought to add to the brialliance of all the others who have responded previously...

Everyone has spoken so far only about the actual charging/dual battery management systems but an important factor to fast charging (and proper power output) is the batteries themselves!!! Yes getting an excellent battery management system is 2/3rds of the problem but the batteries will make all the difference.

Optima batteries are the bomb!!! BUT the price is quite a lot (especially for two), it is worth it though.

chosen

[harlie]

Here are some specifications of the system that I was thinking of installing.

Jaycar 150w Modified Sine Wave $100
or
Jaycar 300w Sine Wave $200.

Jaycar 4 stage 16 amp battery charger $169.




Sorry but this is madness - there is mention of charging the battery faster than it would as a duel battery install. A 16 amp charger will charge faster than the 110amp alternator of the D2???????????
Stick to the duel systems - the marine units (about $100) WILL continue to transfer once the engine is shut down until the voltage drops below the set voltage. As an Electronics Engineer I have installed hundreds of these and never had one that took more than about 30secs to start on the second battery – if it does check the Alternator.
Another point is that all cheaper chargers will 'boil' the battery if left on continuously if there is nothing drawing, this is caused by the cheap regulators have to ‘trickle’ and allowing the voltage to creep too high.

Sorry to be so blunt.

[Quiggers]

chosen:

the first battery in the x1/9 worked from 1977 to 1998

21 years years on a (Magnetti Marelli) battery must be a world record!

GQ

[drivesafe]

Got a genuine question for drivesafe:

What's your opinion of these emergency start packs?

I'm sure you know, Mat, and I've seen them in various junkmail catalogues, usually bright yelloy or red, with short jumper type leads etc, for $100 or less...worth the $, or forget it?

Cheers, GQ

Hi GQ, to be honest, I haven’t had much to do with them because none of the the jump pack I’ve seen had anything but a small battery and seamed a bit useless as an auxiliary battery.

Others with some experience with these devices would be far better at giving any advice.

Cheers and sorry this is of little help.

[chosen]

chosen:

the first battery in the x1/9 worked from 1977 to 1998

21 years years on a (Magnetti Marelli) battery must be a world record!

GQ

Well I haven't even heard of Magnetti Marelli batteries although just visited their web page and couldn't find batteries, perhaps they made them so well that once someone purchased one they never needed another one ;)

21 years, that is UNHEARD OF!!!

Battery technology has come a long way in the last 30 odd years, a long way!

[chosen]

Hi GQ, to be honest, I haven’t had much to do with them because none of the the jump pack I’ve seen had anything but a small battery and seamed a bit useless as an auxiliary battery.

Others with some experience with these devices would be far better at giving any advice.

Cheers and sorry this is of little help.
Yeah, I think that those jump starting packs are a waste of space in a 4x4 vehicle, they almost certainly wouldn't have the AHrs needed for running fridge for long time, a secondary battery with system often takes up less room and is most importantly MOUNTED to the vehicle - much much safer in the event of a roll/crash/rough bouncy sand dune :-)

[Relay]

Yikes, a lot of bother over another battery. Most things have already been said and I dont feel the need for repeating them but, I'll just add a little bit.

If you are terribly worried about your alternator load, which with dual batteries, spotties, fridges and goodness knows what else; you should be. An alternator may be rated at 110Amps but it would turn into a ball of puss before it got close to putting out that kind of spectacular array. The good thing is, that nowadays you can purchase (often multi fit) higher amperage alternators for heavy load situations. And if you're against the bother of trying to squeeze in the pre-built units, take alternator to a specialist and get it re-wound for the whatever amperage takes your fancy. Make sure the diodes can handle that though...or you'll be very grumpy later.

[drivesafe]

Hi Relay, it actually doesn’t matter if you have a load that exceeds an alternator’s maximum output.

The only thing that is likely to happen is that your lights will start to get dull and at that point, it’s time to turn a few driving lights off and let the alternator recharge the battery(s).

Alternators are not only designed to operate to their maximum but you would be surprised how often you actually place current loads on your alternator that exceeds the alternator’s maximum output and no harm done.

Cheers

[mcrover]

From memory, the output amps of the alternator is normally peak amps isnt it?

Cant recall exactly but I wouldnt be wanting to be pulling 100+amps out of an alternator through a 4 to 5mm cable to your battery, something would fail in a cloud of smoke I imagine.:o

[beforethevision]

From memory, the output amps of the alternator is normally peak amps isnt it?

Cant recall exactly but I wouldnt be wanting to be pulling 100+amps out of an alternator through a 4 to 5mm cable to your battery, something would fail in a cloud of smoke I imagine.:o

I'd be donning the asbestos immediately :P

exactly right.

[Redback]

I have just had an SC80 installed as I have an Aux in the car and a trailer battery. This will control the recharging of all batteries while on the go. Many thanks to Drivesafe for his patience with my many questions.

However I do intend to use the inverter-to-recharger option to top up the trailer battery from the AUX battery while set up in camp. This was based on advice from drivesafe in the other thread and assumes that daily driving will keep the Aux battery close to fully charged so you might as well use it at night to top up the trailer. http://www.aulro.com/afvb/showthread.php't=37661&highlight=inverter (http://www.aulro.com/afvb/showthread.php't=37661&highlight=inverter)

However I am finding that the Expensive 10A recharger is not performing nearly as well from the 600w Modified Sine Wave inverter as it does from a mains suppy. In fact it makes a clicking sound every 2 secs approx and makes me nervous that I am damaging it. Plus it takes a long time to start putting out >13.5Amps. Any comments on these symptoms would be appreciated.

Note that the Supercheap 10A recharger seems to work fine, gets to 13.5v quickly.

If this is typical then I don't think it meets the objective for charging fasting (which was dubious anyway according to previous posts).

Mate i have been doing this for a while now, not because i have too, but it's for those cloudy days when we can't use our solar panel.

I have Dick Smith modified wave inverter and a 1.25amp Battery Fighter (brand name) trickle charger i got from Supercheap for topping up the camper battery.

Anyway my point is it could be because the amps of your charger are to high, remember the inverter relys on power from your battery and your combination maybe drawing too much power from the battery causing the clicking, try a trickle charger with less amps similar to what i use.

Baz.

[Quiggers]

Well I haven't even heard of Magnetti Marelli batteries although just visited their web page and couldn't find batteries, perhaps they made them so well that once someone purchased one they never needed another one ;)

21 years, that is UNHEARD OF!!!

Battery technology has come a long way in the last 30 odd years, a long way!

The X1/9 has many Magnetti Marelli electrical parts, I suppose they are (or were) the Italian equivalent of Bosch or Lucas:eek:
When that battery eventually expired, I tried to get another, but no luck, sadly....with Fiat (then) gone from Aussie and only the occasion Alfa being sold here, that was that, maybe... I vaguely recall MM having some quality issues back then, as well...pity...

GQ

[Redback]

Hi GQ, to be honest, I haven’t had much to do with them because none of the the jump pack I’ve seen had anything but a small battery and seamed a bit useless as an auxiliary battery.

Others with some experience with these devices would be far better at giving any advice.

Cheers and sorry this is of little help.

I have a Projecta 400CCA jumper pack that i carry in the Disco, for me it was a godsent, i flattened my main and auxillary batteries at Cadelga Ruins on the Cordillo Downs Rd and i used it the jumpstart the Disco.

I also use it for lighting around the campfire, it also has 17AH of power output, and great for charging mobile phones.
I recharge it from a 12v cig socket in the car.

Great devices i reckon.

Baz.

[drivesafe]

Hi Ron, my dislike of them is not based on them not being able to do a job but on the limited number of jobs they could be used for.

Their small capacity, in my opinion limits the usefulness based on their cost.

Cheers

[mcrover]

The quite expensive one they bought at work is a POS that wont even start a Vanguard V twin petrol engine let alone a car.

It cost about $400 and is yellow and black and quite big and heavy but if the engine doesnt start the first couple of times round then it's useless.

I have got rid of the tiny transformer that came with it to charge it as it had no over charge protection and now plug it into the normal battery charger and it has made a small amount of difference but not much.

I returned it once because they said it must have been not working properly and they told me that we had over charged it and ruined the battery but it said in the instructions that it should stay plugged into the mains unless needed so thats what we were doing.

They replaced the battery but said it wouldnt be covered by warrenty again.

It is good for running a spot light for about 15 to 20mins though but I wouldnt recomend them to anyone.

There is no way that this one would have a chance to start a Disco, V8 or Diesel It wont start any of my 3 cyl NA kubota diesels, will hardly crank them over.

Buy the way, it was purchased through my mobile tool supplier whom no longer deals with them after the trouble he had getting warrenty through them.

Completely useless.

[cookiesa]

For all the cost why not just fit a dual battery and solar panel. No drawing from the main and tops it up all the time, even when your sitting at camp?

Like others have said I can't see any gain, just loss over using the alternator.

We bought a small battery pack from whitworths marine. 17amp pack and charger which we use for running lights etc around camp (fridge stays in car) works a treat for us as we don't tend to be camped long in the one place. About $60 on sale when we got it and a lot more compact than the jump start style. Even came with a carry pack

[feral]

OK, this is all good but I am not convinced either way yet :D


Well, I'm not sure I understand what the issues are here. However I just installed a second battery and one of drivesafes systems. We just had a 5 week trip, with our fridge and camping gear running off the aux. The beauty of this system is I didn't think about it for 5 weeks... it just worked. How good is that. :)


Ok, Ok, I hear you...I am now convinced :whistling::p

I have installed the dual battery using one of drivesafes systems.

Here are some specifications if others would like to install into a D2.

The controller is attached at the end of the fuse box. This position was really the only place to put it that was high in the engine bay and allow the cables to flow through to either end of the D2. The cable used is 18.8mm sq. from main battery to auxiliary battery via a SC 40 controller.

The position of the auxiliary battery is in the drivers side storage bin. Originally I was going to have it in the passenger side but my main objective was to have the battery to be fully charged as quickly as possible. The length and voltage drop would be less as the cables only runs along the drivers side.

The wiring after the auxiliary battery is all 10mm sq. At this stage it powers an Engel 40L fridge, the standard accessory plug in the cargo area and the jayco van. This is run via an Anderson plug and it will only be for the fridge when driving.

The Fullriver AGM HGL 120 a/h sits nicely in the storage bin and allows us to have the liner in its original position. When everything is in and the lid closed, you do not see evidence of a dual battery.


Here are some pics.....

http://www.aulro.com/app/showfull.php?photo=6543

http://www.aulro.com/app/showfull.php?photo=6542

Installing the positive and negative cable underneath was just as intense as some of our deliberations on this subject :eek:

[feral]

This has been lifted from the D3 Zone about Dual Battery problems......




Quote:
Originally Posted by drivesafe https://www.aulro.com/afvb/images/imported/2016/08/768.jpg (http://www.aulro.com/afvb/showthread.php?p=593675#post593675)
Hi jik22 and discomaniac, I’m pretty sure you won’t have any problems with my gear but I am just following up on info that has come to me from a number of different sources.

What’s happening and because of the situation where it happens, my units, because of the way they work, should not be effected but this is what’s occurring and it occurring at the worst possible time.

The vehicle is started in the morning and as it is starting cold, the charge voltage quickly rises to around the 14 volt mark. This is well and truly high enough to turn on any battery isolator. Alls well so far.

Your off on your holidays and drive for a few hours then stop for fuel or a break.

After the break, ( during which time, most battery isolators have cut out because the motor wasn't running ) you start the motor and off you go.

Here’s where the problem is occurring, because the motor is still hot, once the motor is running, the voltage in the newer D3s is not rising much over 13.2 volts which means the other battery isolators are not cutting in again and the auxiliary battery is actually being discharged by the fridge and what ever else may be drawing power from it instead of getting power from the alternator.

The end result is that when you get to your days destination, your auxiliary battery is anything but charge up.

The reason for posting this thread is to try to get as much info as I can on this situation.

BTW a similar problem is also effecting auxiliary battery charging it new Toyota cruises.

Cheers.



Feral's response....

Although I own a D2, this is exactly how things are happening with my auxiliary battery setup.

I have gone overkill on wiring - 18mmsq. using a Traxide SC40 coupled to a Fullriver 120amp/h.

I have a newish battery - 1.5 years - new 120amp alternator and the whole system does not work efficiently.

I have had my discussion with "12 volt power efficiency" and I am over it.

Why?

Just a couple of questions....

What voltage does a battery need to charge? = 13.8 or more.

What voltage should your alternator put out to charge that battery? = 13.8 or more.


Has anyone heard of this....lifted from a caravan site...

"To get heaps of current into a battery you need to supply it with 14.5 V or higher. Most vehicle alternators will not produce this sort of output when the motor is warmed up (due to alternator temperature compensation.) So the battery will not absorb the full current output available from a vehicle alternator."


The guy's user name is DiscoPeter....whats the chance he owns a Discovery?

Why is my Commorore VT 2000 model has a voltage of 14.2 at the battery yet my D2 has 12.8 - 13.6 at the battery which is all dependent on the temperature. The only time I have seen 14 plus volts was when it was about 1 degree and that was at the cig lighter!

I have just been through to Alice Springs and the whole auxiliary battery set up was a disaster. Even after driving for 6 hours the aux. battery would be reading 12.4 at best. How long do you think the battery would last just running the Engel fridge. It lasted less than 4 hours before the cutout tripped out at 11.6 which means the aux battery is technically flat i.e after this point you are damaging the battery.

As you could possibly tell I am totally frustrated with this whole project. I have collected my research and the finding with my experience firmly confirm you cannot fully charge a battery (100%) by using your altenator. There are too many computers controlling the current for it to charge.

Over to you.


Drivesafe Reply.......

Hi Feral, you need to get voltage regulator/alternator checked because ( excluding the D3 ) all vehicles MUST produce no less than 13.8 volts or the battery(s) will never fully charge.

The average voltage of most vehicles is 14 to 14.2, for yours to be running at as low as 12.8, there is something seriously wrong with your alternator.

Being a new one, the voltage reg is probably built in and if it is new then it should still be under warranty.

By the way, although wet cell batteries can be safely charged with up to 14.7 volts, most AGM batteries will not tolerate that high a charging voltage so if you alternator can be adjusted, keep the maximum voltage to about 14.4 volts. This will resolve your charging problems.

One more point, it is nothing more than a myth regarding not being able to fully charge an automotive battery using an alternator IF the alternator is working properly and yours is not.

Cheers
Drivesafe.



Now this is my position.

This problem is well known and has been a discussion for some time. There is nothing wrong with the Traxide system so don't get me wrong on that. Drivesafe has been very helpful and I do not hold him accountable for anything.

It's the theory.

I now am the proud owner of two alternators that give a charge of anywhere between 12.8 - 13.6 - 14.1 volts. At $700 a pop how many alternators would you like me to try before I get a satisfactory charge to the auxiliary battery. I am losing only .2 volts through the Traxide system so there is no reason to look at that.

What I would like to know is the exact working description of a D2 alternator. Is it as what has been said previously that it is temperature compensated?
The alternator most like will output at 14+ volts but only for a brief period and this just replenishes what has been taken out from starting, etc. After this it just idles along i.e 12.8 - 13.6 volts.


Like I said, I am totally lost on this issue..over it.

With this information I do not believe that a D2 alternator will show constant 14+ volts forever for it to charge an auxiliary battery. And this is what you need to charge a battery efficiently.


Leave it with you.

[Blknight.aus]

I got one of the cheapy kmart ones... AS a jump pack its a WOFTAM... (although when the wifes astra struggled to start (couple of turns then the dreaded tickticktcik of the solenoid) it did have enough in it to turn that over

as a portable light, 12v source for the air pumps I use for inflating air mattresses and a weight for the corner of the tent its GOLD, I didnt pay full price for it tho I got it from the broken goods trolly. Its even got a little aircompressor built in thats not much chop on the internal battery but if hooked up to the main battery via the jumper cables actually makes the advertised 120PSI...

[lokka]

Well ive got a projecta jump start pack this one here http://www.projecta.com.au/catalogue/cid/26/asset_id/60/

Its great tho the battery in it has had a hard life and could do with replacement it will start most cars and 4x4's no probs if its fully charged and i mainly use it to run a couple of 2 foot fluros at camp and the pump for the airbeds and it will go for 3 nights running 2 fluros its great ive had it about 4years or more now cost me 100 buck and has saved my ass and many others plenty of times anyone who bags em must be using the cheap cr@py ones as ive had a great run from this one and no complaints :D:D:D:D:D

[drivesafe]

I am losing only .2 volts through the Traxide system so there is no reason to look at that.

Hi Feral, first off there should be no voltage drop through my unit.

One thing that could cause this is that your alternator is just not putting out enough current and because the auxiliary battery is low, there is a voltage drop being created across the system, from the alternator to the auxiliary battery.

Try removing the NEGATIVE terminal from your auxiliary battery, leave the positive terminal in place.

Then, with the motor warmed up and running, try measuring the voltage at your cranking battery.

You haven’t posted what type of cranking battery you are using. I will presume it is a wet cell ( correct me if otherwise ) Even if your cranking battery is low, the very maximum a wet cell type battery draws is 25 amps so your alternator should easily handle this load and you should have at least 14 volts coming from your alternator.

If you don’t then the alternator is definitely the problem.

Start there at let me know what you find.

Cheers.

[drivesafe]

One more question Feral, how often do you drive the vehicle and when you do drive it, how long do you drive it.

Cheers

[Captain_Rightfoot]

Can I say that I had all sorts of battery trouble a while back. Initially I suspected the Traxide system, but after a process of elimination it was of course a charging problem.

Basically LR didn't tighten the earth onto the engine so the battery couldn't charge. You should be seeing 13.8 but from my limited knowledge you'll never see more than 14.2. When I had the problem I would see between 12.6 and 13.2 and nothing was getting charged :o

[feral]

Tried that one.

I placed a jumper cable from negative terminal and earthed this out onto the engine block. It made no difference.

The main starting battery is a Supercharge Gold Series MF 31-931.

Auxiliary Battery is a Fullriver HGL 120-12B.

The Alternator is brand new Landrover 120amp supplied and fitted.


Let me clarify the voltage loss. It is losing .2 volts from main battery to auxiliary battery measured at the posts of the batteries. The main battery is in the engine bay and the aux battery is in the drive side storage bin in the rear of the D2. I think it would be quite acceptable to loose .2 volts considering the length of the cable run.


The length of time driving spent while on holidays was on some days up to 4 - 7 hours. The change of alternator at Alice Springs made no difference to the charge status of the auxiliary battery.

I will try the removal of the negative terminal and take a reading.

Cheers.

[drivesafe]

Hi again Feral, some more questions.

Although it sounds like you have run both cables, do you have both a positive cable and a negative cable run from the cranking battery to the auxiliary or have just run a positive cable between the two batteries and earthed the auxiliary battery to the chassis?

The .2 volt drop over that length of cable is quite acceptable provided this is while there is some form of load, even just the load that a low charged auxiliary battery will cause.

No load and there should be no voltage drop.

Driving those sort of hours should have at least near fully, to fully charged the batteries.

To have low charged batteries after that length of driving means there is a major problem ( obviously ).

Is your cranking battery low and causing starting problems?

Cheers.

[Wilbur]

This has been a very interesting thread. It really is a significant problem using a dual battery system with a modern multi-stage charging system that in some circumstances will output too low a voltage to trigger the dual battery system.

On the surface, it seems that Feral's first suggestion of using an inverter and a separate charger is the only real solution to the problem.

Of course, the savvy operator could when hot-starting after a very short break, simply run their headlights with the engine off for a few minutes to get the battery flat enough to demand full output from the alternator......

Considering older single stage alternators it is also true that many deep cycle batteries DO charge more quickly and more completely if charged at over 14 volts.

Some (single stage) alternators have a remote sensing lead so that the alternator regulates to the actual voltage at the battery without getting tripped up by voltage drops between the alternator and the battery.

In this case, putting a simple ten-cent diode in series with the sense lead will increase the alternator output by about 0.6 volts - ie, from 13.8 to about 14.4 volts. This then gives an excellent charge for both the auxiliary battery and the car battery. Most car batteries are happy at 14.4 volts.

This is a cheap and nasty trick in some ways, but it works pretty damn well and costs bugger-all.

All food for thought.......

Cheers all,

Paul

[cookiesa]

Just a thought..... and Drivesafe I hope will respond with any corrections as I don't have any experience with his product.

Could this be a combination of issues rather than just 1?

I am wondering if the cranking battery has been load tested? My reason is in the past I had a cranking battery that when a multimeter was put on it (engine off) it read around 12.4v so seemed OK. However I was having cranking problems, especially when cold (Diesel BJ40 Landcruiser)

The auxillary was causing problems with not appearing to hold a charge. After much anguish and searching for a bad earth etc etc we tried a new cranking battery, problem solved. No more cranking issue, and the axillary was now also holding charge!

Unfortunately we didn't have access to any "load testing" type battery testers but what led us to trying a new cranking battery (which was only about 8 months old at the time) was isolating the aux battery then using the headlights to gauge battery condition after a couple of very short turn overs it was apparent the battery wasn't holding up well.

The battery isolator was a simple system of a solenoid which was triggered by oil pressure.

Just some food for thought. Some of the other more knowledgeable may be able to "explain" this a little better!

[drivesafe]

Hi Wilbur, actually, all automotive type batteries, Flooded Wet Cell, Gel Cell and AGM Batteries will charge quick, the higher the charge voltage, providing the current is also available.

The BIG problem is that both Gel Cell and AGM batteries can easily be irrevocably damaged by high charging voltages and additionally, AGM batteries can be damaged by high charging currents.

Those old type diode isolators which never allowed batteries to charge properly, actually work quite well in vehicle fitted with an alternator that requires remote sensing, for the very reason you described.

In this case there is a fault of some kind as it is not normal for any alternator to run at voltages as low as 12.8 unless there is a particularly heavy load being applied to the vehicle’s electrical system. This does not seem to be case.

Poor earth connections can cause this problem but with a poor earth connection at the alternator, you usually get voltage run away where the alternator produces anything up to 18 volts and cooks batteries.

But, a poor earth elsewhere can easily hamper a battery’s ability to charge properly.

[feral]

The negative cable from the auxiliary is wired in combination of both to earth and to the battery.

The cable comes off the battery and is earthed at the point under the floor near the filler cap in the rear of the D2. The cable then continues on and goes all the way to the engine bay to the earth point near the fuse box. This earth point is 25mm away from the Landrover earth point that wraps around the negative cable which leads 75mm to the negative battery terminal.

In regards to the load test, it was tested at Alice Springs and it was deemed to be OK for use. All the testing equipment that Landrover used suggested that the battery was fine.

The Traxide controller appears to be working. If you observe when you start the car the yellow light continues to flash for about a minute and then it transfers to full on.

Does this make sense?

[drivesafe]

The Traxide controller appears to be working. If you observe when you start the car the yellow light continues to flash for about a minute and then it transfers to full on.

Does this make sense?

Yes and this means that the vehicle voltage is rising to at least 13.4v otherwise the SC40 would not cut in BUT, under normal operations, the SC40 would cut in in about 10 seconds. The longer delay in cutting in is indicating a vehicle voltage problem of some sort.

The earth sounds fine.

All this is not much help but it is eliminating things and the problem is still looking like being the alternator.

Cheers

[HangOver]

So ......................
What is a normal range of voltages for:

1. a properly charged battery, (disconnected)
2. an alternator that is working correctly

I know different batteries/alternators will most likely have different voltages but when is it time to get a new battery/alternator.

eg when the battery is less than 11.5 volts or an alternator that puts puts out more than 16v or less than 14v or whatever, (just examples).

[cookiesa]

Depending on how mechanical you are it looks to me like time to pull out the alternator and do the bushes and bearings and give it a good clean up.

Or off to an auto electrician (assuming your out of warranty of course) and get your alternator done.

[drivesafe]

Hi HangOver, just measuring the battery terminal voltage won’t work because a battery can be stuffed but if there is no load on it, it can still show 12.8v ( a fully charged battery’s voltage )

The only effective way to test a battery is to have it load tested by an auto electrician and this is normally done for free.

The obvious sign that the battery is on it’s way out is when the alternator is producing a constant output of around 14v and the battery is just not holding a charge.

The problem with a low voltage charge like what Feral’s alternator sounds like it’s doing, is that the battery WILL get some charge and in this case, enough to continue to start the vehicle.

BUT, the battery can never get fully charged or even near a full charge and if this situation continues, for even a sort period of time, the battery will have a VERY short operating life.

Cheers

[feral]

Depending on how mechanical you are it looks to me like time to pull out the alternator and do the bushes and bearings and give it a good clean up.

Or off to an auto electrician (assuming your out of warranty of course) and get your alternator done.


:D:D:D:D:D:D:D.....IT'S A BRAND NEW 120 AMP LANDROVER SUPPLIED AND FITTED ALTERNATOR.:p:p

I must be the most un-luckiest bloke around to score something new that is stuffed.....



Oh, hang on..that's not right.....Ron is :wasntme:

[cookiesa]

I was under the impression the MM 120amp was only suitable for the V8 engine.... Bugger I just bought the 100amp one..... but only paid $335 so I'm happy!

(Not that the alternator capacity is relevant to this!)

Maybe a long shot but if you are certain it is not the alternator itself, How is the drive belt tension/condition? If it is slipping you may not be getting sufficient speed on the alternator to charge properly. (especially when put under load) This may also mean your "charge" light isn't coming on to indicate there is a problem.

[Frontier1]

All this with the batteries, dual, ect, has got me wondering.

I have a dual battery setup using the old Jaycar kit that you had to put together and install yourself. Have had it running now for a couple of years and it's been great. I actually had the setup done since I ran my boat winch off the back.

Anyway, I am wondering ( Drivesafe & Harley?), whether the new jaycar product Battery Isolator by Steed ( 70amp ) might also be the way to go. The unit is $99.95 and I figure $32 in cabbles and $7 for clips/plugs.

How would you guys rate this compared to either your own sytems or other ones on the market.

I'm wondering this as I think I might install this in the boat as I have has a dead battery scenario recently due to keeping the accessories on and only having the cranking battery to run the lot off. ( Now have two batteries since I had to buy a new Pro 600 series. )

Cheers,Pete'

[drivesafe]

Anyway, I am wondering ( Drivesafe & Harley?), whether the new jaycar product Battery Isolator by Steed ( 70amp ) might also be the way to go. The unit is $99.95 and I figure $32 in cabbles and $7 for clips/plugs.

Cheers,Pete'

Hi Pete, post us a link to the product so we can see what it is.

Cheers.

[Frontier1]

Knew you were going to ask that!

http://jaycar.com.au/productView.asp?ID=MB3670&CATID=&keywords=Battery+Isolator&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

Seems a simple enough setup, even for me!

Cheers, Pete'

[drivesafe]

Hi Frontier1, that device is an absolute NO NO.

Their a diode isolator type and as such, have loads of drawbacks.

The main draw backs are that the lower the battery, the longer these take to charge the battery compered to ordinary relay type Isolators.

Unless you can trick up your voltage regulator ( not recommended ) you will never fully charge your battery and because of the point, you will most likely shorten the operating life of your battery.

Cheers.

[cookiesa]

If this is the correct one...

http://www.jaycar.com.au/productView.asp?ID=MB3672&CATID=&keywords=battery+isolator&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

Then the way I read it it isn't a true dual battery system in the sense of the way we use them. It draws from whichever battery has the higher voltage. To me it reads it will switch and drain from both however 1 dead battery can't flatten the other. More for protecting a battery in a "bank" than isolating them

[drivesafe]

If this is the correct one...

http://www.jaycar.com.au/productView.asp?ID=MB3672&CATID=&keywords=battery+isolator&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

Then the way I read it it isn't a true dual battery system in the sense of the way we use them. It draws from whichever battery has the higher voltage. To me it reads it will switch and drain from both however I dead battery can't flatten the other. More for protecting a battery in a "bank" than isolating them

Yep, that one seems a strange device and not that sure where it would be used in an automotive set up.

Out of pure curiosity, has anyone got any suggestions on it’s use, other than the one cookies click to.

[Frontier1]

Ok, fair enough and I always listen to those that know more. (ya' learn more that way!)

So what is the easiest and cheapest solution for what I want, knowing that I want a fully charged cranking battery and power left over charging my accessory battery?.

Plus that in an emergency I can start my car/boat, what have you, from my 2nd battery <or is it as simple as a set of jumper leads from Bat2 to Batt1>?

Thanks guys and sorry if this is rehashing what has gone before in this thread:)

Cheers Pete'

[PhilipA]

I hesitate to chime in BUT.
I have 2 alternators ( both 85 AMP Bosch type)and two batteries, run completely separately.
I have a Jaycar volt meter switched between the two batteries ( which I have checked to be accurate).
Both alternators run at between 14 and 14.5 volts depending on temp, when the batteries are fully charged, usually at the upper end say 14.4.
Recently I noticed that the starting battery alternator voltage would fluctuate down to 13.7 volts. I placed a Megapulse on the battery and the charge level went up to 14+, after afew days.
I recenty boughta Supercharge "All Rounder" to be starting battery.
I noticed some interesting things
1 The charge level is now always 14+ and nearer 14.5.
2 the charge level under high load eg aircon is now 14+ wheras before it was about 13.7. This is strange to me as one would think that once going and charged for a while the battery should have no bearing on the system voltage. ie under a similar load the system level should be the same with an old or new battery.
But it isn't so.
The other thing I notice is that my 95 AH AGM will accept about 80-90% charge in about 90 minutes from say 11 volts. At this level my system voltage is about 13.7 volts. It then will rise slowly over say another 3-4 hours to 14.4 volts. remember this alternator is ONLY charging the battery, so is governed by the battery. ( Well the Engle is taking 1.5 AH or so)
So my conclusion is that you get quite a lot of charge in the first short time but the final top up takes quite a while. This will happen regardless of whether you are using an alternator or smart charger as it is the nature of batteries.
Regards Philip A

[drivesafe]

The other thing I notice is that my 95 AH AGM will accept about 80-90% charge in about 90 minutes from say 11 volts. At this level my system voltage is about 13.7 volts. It then will rise slowly over say another 3-4 hours to 14.4 volts. remember this alternator is ONLY charging the battery, so is governed by the battery. ( Well the Engle is taking 1.5 AH or so)
So my conclusion is that you get quite a lot of charge in the first short time but the final top up takes quite a while. This will happen regardless of whether you are using an alternator or smart charger as it is the nature of batteries.
Regards Philip A

Hi PhilipA, that’s a very good observation and is exactly how ALL batteries ( not just AGMs ) charge.

[Wilbur]

Hi Drivesafe,

That Jaycar device is almost certainly the same device, but with the diodes reversed, ie, with the load coming from the junction of the two, and each other end of the diodes going to the two batteries.Thus the load will draw from whichever battery has the highest voltage - except that 0.6 ~ 0.9 volts will be lost across the diode.

Basically not much use at all!

Cheers all,

Paul

[Dougal]

For sh*ts and giggles I tried this today.
Plugged inverter into cigarette lighter and battery charger into inverter.

According to my clamp-meter it drew 3.1 amps from the socket to provide 1.7 amps at the battery posts.:cool:

[drivesafe]

Hi Doudal, very interesting and it would seem to be highly inefficient BUT need a few more details, such as the voltage at the cigarette lighter, the voltage at the battery posts and what is the size of both the inverter and the battery charger ( in watts if possible ).

Cheers.

[Dougal]

Hi Doudal, very interesting and it would seem to be highly inefficient BUT need a few more details, such as the voltage at the cigarette lighter, the voltage at the battery posts and what is the size of both the inverter and the battery charger ( in watts if possible ).

Cheers.

Not highly inefficient, 1.8/3.1 = about 60%.
For my experiment the charging battery and the source battery are the same.
The inverter I was using is only 300 watts but when drawing 3.1 amps is only running at a fraction of it's capacity.
I need to split out a single wire (either phase or neutral) to be able to measure the AC current from the inverter. I didn't do that.

The battery charger is rated at 4 amps but I've never got more than 2.2 amps out of it. It's a trickle charger, the sort that tops up a battery overnight. It can't compete with an alternator for stoking up a battery.

[drivesafe]

For my experiment the charging battery and the source battery are the same.

I suspected that.

This idea WHEN USED WITH TWO BATTERIES, can be very useful for topping up camp fridge batteries over night, using the vehicle battery without the risk of flattening the vehicle battery.

[Dougal]

I suspected that.

This idea WHEN USED WITH TWO BATTERIES, can be very useful for topping up camp fridge batteries over night, using the vehicle battery without the risk of flattening the vehicle battery.

How can you top up battery #2 by using battery #1 without flattening battery #1?
Remember you're taking 1.5 times the juice from #1 that you're putting into #2. Asking #1 to still start the car in the morning sounds a little much.

IMO you need a 12v split charging system which works when the engine is running.

[drivesafe]

How can you top up battery #2 by using battery #1 without flattening battery #1?
Remember you're taking 1.5 times the juice from #1 that you're putting into #2. Asking #1 to still start the car in the morning sounds a little much.

IMO you need a 12v split charging system which works when the engine is running.

If you have the equivalent of a 100 A/H cranking battery, you could safely hook up the your inverter to the cranking battery, run a 240 VAC extension cord to the fridge battery and your battery charger and let it run over night.

Say you connected up at 6 pm and let it run to 8 am, even pulling the full 3.1 amps, you cranking battery would still have about 12.2 volts which is heap enough to start even the most stubborn diesel motor on the coldest morning at lest a couple of times.

If you had a smaller battery then yes it would pay to have an SC40 Dual Battery controller, which allows the cranking battery to be discharged down to 12 volts before isolating.

This has been covered before, elsewhere on the site but I can’t remember where plus, I am getting a tad of subject so I’ll leave it at that.

Cheers.

[Relay]

The idea of smart starting is to ensure you primary battery starts you in the morning. The standing voltage of a battery doesn't mean much. You can have 11.8V in a battery and it might still start the car. You can have a surface voltage up to 13.6V in a battery (directly after charging) and it might -not- start the car. Voltage is -not- what starts your vehicle. The cold cranking amperage is what's really important. It requires around 40Amps per cylinder to crank an engine to firing speed (very roughly speaking). If your battery can do that, great. The killer is the fact that on most engines it needs to put out those amps and -still- have a voltage above 9.6V...why? So your ignition system works! Common problem on old (VK-L) commodores as their computers wouldn't work under 10V, due to computer design. Manufacturers have fixed that fault since then.

The simple answer, if you want to start in the morning, dont drain your primary battery overnight. All it takes is the right heat/chill combination to crack the plates of a battery. They can fail, at the drop of a hat. An alternator will cope...if it doesn't, get it looked at. (Provided you're not driving around with several hundred watts of accessory lighting or some other rediculous power draining equipment.)

[drivesafe]

Hi Relay, taking a healthy battery down to 12 volts over night or over a few nights won’t create a problem with starting.

A battery thats on it’s way out will have a problem at 12 volts but the same battery will in a very short time have a problem at 12.8 so a dud battery is not really relevant.

As far as taking a battery down to 12 volts and then starting, I’ve been doing that for that for 19 years now or more to the point, my gear has and as there are thousands of them out there, definitely not a problem starting off a battery with 12 volts SoC.

Cheers

[Relay]

I dunno about you darlings...but seriously, how often do you check to see if you're battery is healthy? Perhaps I'm just lazy...really lazy considering I have a tester at work that takes all of 5 minutes.

:D. I suppose I'm just cynical, on account of the amount of people I have to go jump start (our own cars included!)

[DEFENDERZOOK]

ive got one sitting here at home.......and i dont bother to test my batteries......


as far as im concerned....its either working or its not......
if i get stuck.....i can just ring SWMBO to come and pick me up or jump start me......

if i was to go on a long long long long...........long drive across oz on my own say.......
then i would definitely be either testing or replacing the batteries prior to the trip.......


out in the middle of nowhere is not a real good time to discover your battery has finally dropped a cell......

[drivesafe]

as far as im concerned....its either working or its not......


I have a load tester here and I'm forever testing other people’s batteries for them but I’m with zook on this one.

I honestly have no idea when I last tested ANY of my own vehicle’s batteries.

Cheers

[Dougal]

I honestly have no idea when I last tested ANY of my own vehicle’s batteries.

Cheers

The last time I turned the key was my last batteries test.
It passed.

[drivesafe]

The last time I turned the key was my last batteries test.
It passed.

:Rolling::Rolling: Good one, I’ll remember that for my next winging customer.

Cheers.

[DEFENDERZOOK]

i liked that too.......

how much whinging do you get when you test a customers battery and it fails......according to the computerised tester......
yet everything still works fine......and the customer just cant fathom the fact the battery isnt up to capacity.....