DC-DC charger- which one?

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Originally Posted by drivesafe

Hi Silenceisgolden and sorry mate but that is straight out of the advertising B/S they use to try to convince people that an alternator can't charge batteries but these wonder devices can.

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Dunno. I don't read advertising. I spent my working life designing electronic equipment and one project was designing and building in Australia a product that incorporated a very early adoption battery management system. For this I relied heavily on generous information from Sonnenschein batteries, back then the leaders in the field. This product was manufactured under the brand name of a Japanese based multi-national, a permission not lightly granted. I am not fully up to date with modern battery types such as Lithium, but am up to speed on AGM's.

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Originally Posted by drivesafe

First and foremost, the charging algorithms of DC/DC devices are a copy of how battery chargers operate.

As such, battery chargers can be connected and charging batteries for many months at a time.

This is why they have a float mode. If you kept a constant voltage of 14.4v on a battery, after about 24 hours, you would start to DRY the battery out.

So to avoid DRYING OUT the battery, these devices MUST lower the voltage being applied to the battery.

Exactly. The DC-DC charger can do this, the alternator does not. A 'smart' alternator will drop voltage to suit the cranking battery, not the house battery.

If you apply a constant voltage of 14.7 or higher, you will end up cooking a battery. Again, to avoid cooking batteries, chargers do not stay at such high voltages for very long. ( time depends on the chargers make and model )

Now as DC/DC devices use the same style of electronics as battery chargers, its just simpler to use the same algorithms.

It is as simple as that.

As for alternators shortening the operating life spans of batteries, there is not only no evidence to back that advertising crap, but reality and 60 to 70 years of RV use clearly demonstrates the exact opposite is the case. Just more misleading advertising hype, used to try to convince people they need something that will achieve nothing over what an alternator can do.

Now some real facts. How many times have you heard of an alternator cooking batteries, can't happen, but you hear of plenty of cases where DC/DC devices have cooked batteries.

How many vehicle manufacturers advise not to have a fridge powered from any battery being charged from the vehicles alternator?

There are a number of brands of DC/DC devices that state exactly that. You must not power a fridge from any battery being charged by their DC/DC device, because the fridge cycling on and off can cause many DC/DC devices to overcharge the battery.

Yes, this happens because as in my post, safe charging requires the voltage to drop to a float level when the battery draw drops to a specified level. If the fridge is running at the time when absorption should end, the current draw can trick the charger into thinking that the battery still requires more absorption charging. However, as soon as the fridge cycles off, the charger goes into float mode, so it is not a great problem with compressor type fridges. But note - your alternator will NEVER go into float mode to suit the house battery, so it WILL be overcharged and have its life reduced.

Then there is the problem of mixing battery types. Not recommended when using a DC/DC device.

Perfectly safe with a DC-DC device. Most allow you to select the profile of the house battery. Mixing should not be done with an alernator.

Yet when using an alternator, not only can you have any number of mixed battery types but they will each be charged at the optimum charge rate for each battery, regardless of type or state of charge. Can't do that with a DC/DC device ( or battery charger ).

Sorry mate, you have that the wrong way around. Maybe it is you who have been reading advertising B/S.

With all the wonder devices on the market today, alternators are still the ultimate and safest way to charge any type of lead acid battery.

I could go on but most of you will get the CORRECT picture.

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Originally Posted by Eevo

whats the difference between a house battery and car battery?

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One starts your car..

The other one starts your house?!

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Originally Posted by Silenceisgolden

Sorry mate, you have that the wrong way around. Maybe it is you who have been reading advertising B/S.

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Sorry, but it is you have it the wrong way around. No advertising BS, just that I understand physics. Alternators quite happily charge a mix of batteries and the batteries happily charge and live a long life. I have 3 different types in my system, and all stay fully charged and happy with just the alternator doing the work.

Notice that on DC DC devices and chargers the battery type is set from a menu or switch - so it knows what charge rate, voltage, etc to run at. My alternator doesn't ask what type of battery I have.

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Originally Posted by drivesafe

If your D4 is cycling down to 12.2v, then your cranking battery is being discharged while you drive and that is not the intended operation of any alternator, with exception of the Stop/Start setups, where they have their own separate battery.

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No mentioning of B/S, Crap or claiming others are falsely advertising from me... I will stick to the subject.

I think many of our D4s are cycling down to 12.2v for periods of time. As most of us don't monitor voltage constantly we just wouldn't know.

I have spend a fair amount of time searching the net for a good explanation of variable voltage alternators and how they save fuel. There isn't much on the net but here are two articles. One states batteries getting down to 12.5V. It seems Land Rover may have taken that a step further.


Century Batteries:
[ame="http://www.centurybatteries.com.au/content/documents/battery-talk/issue-4-battery-talk-regulated-charge-control.pdf"]http://www.centurybatteries.com.au/content/documents/battery-talk/issue-4-battery-talk-regulated-charge-control.pdf[/ame]


AGCOAUTO
http://www.agcoauto.com/content/news/p2_articleid/350


So we know that the car will use some cranking battery capacity to drive the cars electrical systems under certain conditions. When this happens voltage may drop to 12.2v for a period of time. The longest I have seen so far is about 10 minutes. The Body Control Module monitors battery state of charge and the state of the car (accelerating, cruising, coasting) to determine how it will use alternator power to charge the battery. The algorithm used and its exact parameters is not knows (except by some boffin at Land Rover). It may include the capacity and chemistry of the car battery.

While the car is operational the systems will monitor and track battery capacity. It will see any devices drawing current (including any DC/DC charging devices).

However when the car is asleep (switched off) it is probably that the BCM will not be monitoring what is being drawn from the battery. Therefore a second battery system connected directly to the car battery or that interferes with the SOC of the car battery while the car is asleep may cause confusion to the algorithms that manage the car battery.

A DC/DC charger can not cause this confusion. It is only active when the car is active and is fully visible to the body control module.

Yes, my car drives around at 12.2v from time to time. It did that before I fitted the DC/DC charge. It still does it now. I don't expect any cranking battery problems as a result.

See... no colourful language, blame, angst or provocation. I hope we see the same in any responses to my theory (with some evidence).

Originally Posted by drivesafe
First and foremost, the charging algorithms of DC/DC devices are a copy of how battery chargers operate.

As such, battery chargers can be connected and charging batteries for many months at a time.

This is why they have a float mode. If you kept a constant voltage of 14.4v on a battery, after about 24 hours, you would start to DRY the battery out.

So to avoid DRYING OUT the battery, these devices MUST lower the voltage being applied to the battery.

Exactly. The DC-DC charger can do this, the alternator does not. A 'smart' alternator will drop voltage to suit the cranking battery, not the house battery.

First off, how many vehicles have smart alternators, or the correct terminology is VARIABLE VOLTAGE ALTERNATORS.

Even today, most vehicles have alternator voltage levels that never go below 14.2v, so why do all these vehicle not have the problems you fictisiously claim they will. Once again, reality proves you wrong.

But lets forget REAL facts for now. Above, in this post, you stated A 'smart' alternator will drop voltage to suit the cranking battery, not the house battery.

Then you state. But note - your alternator will NEVER go into float mode to suit the house battery, so it WILL be overcharged and have its life reduced.

So according to you, an alternator both drops its voltage but still manages to over charge the house battery. Now thats one clever feat.

Mixing ( battery types ) should not be done with an alernator

It is a well established FACT that an alternator can SAFELY and properly charge banks of mixed battery types and does it far better than any other charging system. And this is fact, not your fiction.

Enormous amount of CSB in this thread....

People challenging facts whilst presenting none of their own... And always pushing the DC-DC hype.

Those with DC-DC chargers; that's fine... But here is the only valid argument for your set-up.

"I spent a lot of money on an electrical DBS charging system that works for me."

Any other attempt to justify such expenditure/complexity is defying simple physics and electrical knowledge.

There is not a Land Rover out there at this point in time that requires such a system to effectively charge or maintain their Multi-battery installation.
(Assumption: Wiring and connections/storage cells are up to scratch)

Peter, I have no idea what your reason was for posting that document. It pretty well confirms what I have been posting.

If you discharge a battery down to 60% SoC or 12.2v as you claim is happening, then it will take quite a few hours of continuos driving with an alternator voltage of 14.4v, to recharge that battery.

This is something I have already pointed out and that info is in the document you just posted up.

But you yourself stated you could not find any reference to batteries being discharged any lower than 12.5v or 90% SoC.

And just for your info, the EU has had these Emission Control Regulations in place since 2005 and hence the reason why the D3 was one the first vehicles in Australia with Variable Voltage Alternators.

So if your D4 is running at 12.2v, ( and I suspect its just the voltage readings not the actual battery voltage level ), but if your battery is running that low, its not going to last very long.

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Originally Posted by RoverLander

While the car is operational the systems will monitor and track battery capacity. It will see any devices drawing current (including any DC/DC charging devices).

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Actually, the D4 can not see any other current draw other than the cranking battery itself., That is the only current draw the D4 is set up to monitor.

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Originally Posted by RoverLander

However when the car is asleep (switched off) it is probably that the BCM will not be monitoring what is being drawn from the battery. Therefore a second battery system connected directly to the car battery or that interferes with the SOC of the car battery while the car is asleep may cause confusion to the algorithms that manage the car battery.

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There is a little problem with this theory in that most D4s that have had a problem with low operating voltages are in the Uk and almost none of them had any form of dual battery system fitted. The problem was as stated, is a software problem, and once the software is updated, as has been the case here as well, the problem ceased to exist.

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Originally Posted by RoverLander

No mentioning of B/S, Crap or claiming others are falsely advertising from me... I will stick to the subject.

I think many of our D4s are cycling down to 12.2v for periods of time. As most of us don't monitor voltage constantly we just wouldn't know.

I have spend a fair amount of time searching the net for a good explanation of variable voltage alternators and how they save fuel. There isn't much on the net but here are two articles. One states batteries getting down to 12.5V. It seems Land Rover may have taken that a step further.


Century Batteries:
http://www.centurybatteries.com.au/content/documents/battery-talk/issue-4-battery-talk-regulated-charge-control.pdf


AGCOAUTO
http://www.agcoauto.com/content/news/p2_articleid/350


So we know that the car will use some cranking battery capacity to drive the cars electrical systems under certain conditions. When this happens voltage may drop to 12.2v for a period of time. The longest I have seen so far is about 10 minutes. The Body Control Module monitors battery state of charge and the state of the car (accelerating, cruising, coasting) to determine how it will use alternator power to charge the battery. The algorithm used and its exact parameters is not knows (except by some boffin at Land Rover). It may include the capacity and chemistry of the car battery.

While the car is operational the systems will monitor and track battery capacity. It will see any devices drawing current (including any DC/DC charging devices).

However when the car is asleep (switched off) it is probably that the BCM will not be monitoring what is being drawn from the battery. Therefore a second battery system connected directly to the car battery or that interferes with the SOC of the car battery while the car is asleep may cause confusion to the algorithms that manage the car battery.

A DC/DC charger can not cause this confusion. It is only active when the car is active and is fully visible to the body control module.

Yes, my car drives around at 12.2v from time to time. It did that before I fitted the DC/DC charge. It still does it now. I don't expect any cranking battery problems as a result.

See... no colourful language, blame, angst or provocation. I hope we see the same in any responses to my theory (with some evidence).

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gunna be fair here we asked for evidence, fact and proof, you gave us an advertising blurb from a battery company on that I'd probably, without further research, consider betting is involved wit ha susiduary company that manufcatures DC/DC chargers and other gubbinary that is efectively just a poor substitute for some proper reseach and application of knowledge. of course why bother going to that effort when for just the low price of, you dont have to and hell for just $15 more we'll even arrange installation.

claiming the BECM will always know whats being drawn out simply isnt true if you've patched a DC/DC charger (or any other load) into the system where the amps its drawing cant be monitered then the becm wont know how much charge is making it to the battery. IF its got the alternator out put set to 15 amps because it knows the state of charge is 80% and that the car only needs 14 amps to meet the switched on loads if you've got a DC/DC in there thats pulling an unseen 10 amps to put 3 amps into your second battery and run your fridge then your cranking battery is slowly discharging.

its entirely possible to develop the situation where with the battery being pulled down by the DC/DC charger and then robbing the expected amps that are supposed to be going back into the battery leaving it in a lower than expected SOC.

so lets say you wind up a number of short drives on a nice warm afternoon, with a cosey battery, the BECM has shut down with what it thinks is a 60% battery thats enough or a start. you park up the vehicle it rains and theres a cold snap overnight. its first thing in the morning now and you goto crank it over, the starter engages and the battery voltae dips to 10.2v. What happens?

now at this point its your call.

I can quite easily diatribe on about the facts about dc/dc chargers and tell you that I'm trying to teach you thats option one but I dont reckon its going to work.

OR

I can rip open a thread and do q/a on everything you've thrown uprange we'll call it a ranging shot and I'll give you some little corrections and let you shoot again and we'll just keep doing that and eventually you'll bracket yourself in and drop some around the target then with simple logic and evidence you'll drop the next salvo on target. I'll call it learning, you'll call it everything but right up untill you hit the straddle and then put the rounds on target. then you'll call it knowledge.

Or.

we can simply run with everyone can have their own opinion. Just beware that unlike people opinions are not all created equal some are a great deal more researched and robust than most.

so far your "research" is an adverstising blurb and your pushing up against some substantially qualified and experienced persons here.

as a final freebie bit of advice. look up right, numbers while manipulable dont generally lie by themselves.

I can never understand why people think a DC-DC Charger does a better job than an alternater, this means that all the car manufacturers in the world are wrong and the manufacturers of DC-DC Charger are right and know better.

I have a friend that has a setup that doesn't use any form of DBS or DC-DC Charger, he uses the alternater to charge both his batteries, he uses a battery clamp switch to isolate his batteries when stopped, it's a manual version of a DBS basically, as well, when he had his camper, it was the same, the wire ran back to the camper and the alternater charged that battery as well, now I've known Howard for a long time and I can tell you, he's no dill, tight maybe(Scottish heritage) he's been doing this long before I've known him, so if it has been working well for all these years via the alternater, why use a DC-DC Charger, trust me, if there was a better way that saved Howard money, he would do it.

Baz.

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Originally Posted by Redback

I can never understand why people think a DC-DC Charger does a better job than an alternater, this means that all the car manufacturers in the world are wrong and the manufacturers of DC-DC Charger are right and know better.

Baz.

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Nor can Drivesafe or Blknight understand it, but it is not that complicated really. The requirements of the house battery and the cranking battery are quite different, and hence different types of batteries are used and require different charging regimes.