Charging Deep Cycle in my camper

[wardy1]

Just got back from a great trip in the Ben Boyd NP. Only problem I had was trying to keep the power up to my deep cycle battery in the camper trailer.
In the end, I swapped my normal battery over for the deep cycle and went for a drive for a few hours (Eden and surrounds) and it was fine. Although this worked, as we all know, the batteries are bloody heavy!:o
Hoping that Drivesafe may read this thread but advice/ideas from all members appreciated as always.

[drivesafe]

Hi wardy1, from what you have posted, the most likely cause for your deep cycle not charging is the cable size.

Any idea of what size cable you have and do you have both a positive and a negative cable running through the tow vehicle and not just earthed the negative to the chassis at the rear of the tow vehicle.

This is a start and I will see what I can help you with once I know more about your set up.

Cheers.

[Pedro_The_Swift]

I'm just about to test my setup with The Cooma trip,, (if it doesnt work I'll never hear the end of it:p:p)
You dont mention how long it took to discharge the battery, what discharged it, or the battery size.


http://www.aulro.com/afvb/technical-chatter/39419-charging-aux-battery-trailer.html
this may help,, or not, but its worth a read just for the banter--:D

[wardy1]

Hi guys and thanks for the replies so far.
Currently I have 6mm cable to an Anderson plug running off my main battery.
Whilst running, I have a 3 way fridge running in the trailer (and yes, it draws heaps). I have a Waeco running off the second battery in the Disco.
As soon as we set up, I change the 3 way over to gas so from then on, the deep cycle mainly runs a couple of lights or is used to back up the second battery to run the Waeco (via a set of jumper leads).
I really thought 6mm would be enough but I'm more than willing to accept that a larger diam cable is req'd. If I upgrade the cable on the car, will I also need to upgrade the cable on the trailer side of the anderson?
Drivesafe you can call me on 0417 367 625 if its easier.
Alan

[drivesafe]

Hi wardy1, your problem will mostly be solved by replacing the cable, in the Disco and the trailer.

The 6mm is 6mm auto which is actually only 4.5mm2 which is way, WAY too small.

You need to run nothing smaller than 6B&S ( 13.5mm2 ) from the Main ( cranking ) battery to your trailer’s battery via the Anderson Plug.

That should pretty well solve all your charging problems.

Cheers.

[EchiDna]

related question Tim....not to steal the direction of the thread starter...


is it possible to go too big with the wire dimentions? reason being, I've got a roll of 50mm2 double insulated welding wire running around here somewhere - could I use that for charging a second battery?

[kaa45]

related question Tim....not to steal the direction of the thread starter...


is it possible to go too big with the wire dimentions? reason being, I've got a roll of 50mm2 double insulated welding wire running around here somewhere - could I use that for charging a second battery?

Short answer: Bigger the better.....less resistance.

In the real world.....weight, flexibility, etc

[justinc]

:TakeABow:Drivesafe...:D:p

I had a similar experience when doing a hurried mod to switch my 2nd batt from the left to the right in the back of the RR to make room for the roller draws. Ran a longer cable across, in an inferior diameter, (I'm not saying how small, incase Drivesafe reads this and shakes his head in disgust) and lost 2 volts between the alternator and the aux batt. 14.8V down to 12.8V!!!

In this case though, the earth was the major culprit. I ran a larger one straight to the body and picked it up to 13.7V, which is OK for now. When the camper trailer gets here, In goes one of Tims SC80 caravan/ trailer 3 battery systems. Immediately.

Volt drop sucks.

JC

[drivesafe]

Hi EchiDna, as kaa45 posted, bigger is better.

If you have some 50mm2 cable, use it and it will be better than using 13.5mm2.

The reason for posting the minimum recommended cable size as being 6B&S (13.5mm2 ) is that a number of factors have to be considered when choosing cable for use in a dual battery system.

The thickness of the cable and the distance between the two batteries are the main factors but you also need to consider the total stored capacity of the the auxiliary battery(s) and how much of this capacity is likely to be used on a regular basis, each time you go on a trip.

This last factor is usually the hardest to determine in advance of actually using the system but can be a major factor in how your batteries are recharged.

For example, if you have a long run between the cranking battery and the auxiliary battery(s) and you know your auxiliary battery is only going to be used to supply power over night and then be charged up each day as you will be driving every day. As the amount of stored capacity needing to be replaced is not going to be that great and as the auxiliary battery(s)’s State of Charge ( SoC ) is not going to be low, the amount of current needed to recharge the battery is not going to be high so there is not going to be much of a voltage drop, all of which means your battery(s) will be charge in a relatively short period of time.

Special Note, in many references to using auxiliary batteries, there is an extremist fanatical opinion that you need to fully recharge the auxiliary battery after each use, BOLLOX. In the above type of use and in many holiday type uses, it is not necessary to fully charge the auxiliary battery(s) but simply replace the bulk of the charge by bringing the auxiliary battery(s) up to 85 to 90% of full charge state will easily cater for most users requirements and will not have any detrimental effect on the auxiliary battery(s)

Fully charging the battery(s) at the end of a holiday or at periodical time during a long holiday will keep the battery(s) healthy.

Now, in the situation that wardy1 has, the deep cycle battery is probably not going to need all that much to recharge it but the current needed to recharge the deep cycle battery is supplied down a cable that is also powering a fairly thirsty fridge so 6B&S is the absolute minimum size cable that would run the fridge and top the battery up at the same time.

A point to remember is that with this type of fridge, getting a higher voltage, it is going to run more efficiently and therefore need less current to run it thus reducing the load on the cable supplying both it and the auxiliary battery.

In this situation, you could run thicker cable but there comes a point where the cost of thicker cable starts to out weigh any potential gain of having thicker cable.

If, on the other hand, you were in a situation where you were using a fair bit of the stored capacity of your auxiliary battery(s) between charges then thicker cable would be of greater advantage, particularly in reducing the charging time which equates to the amount of driving time needed.

Cheers and sorry for the reply being so long winded.

[drivesafe]

Hi justic, it surprising how cable size ( and distance between batteries ) can effect charging.

If you had two batteries side by side, there would be little difference in charging time whether you used 6mm auto wire or 50mm2 cable, the distance in the case is the governing factor.

[kaa45]

Hey Drivesafe,

That wasn't "long winded". It was concise and yet simple. The best explanation I've seen in a long time without getting technical (Ohm's law and alot of maths).

Bloody well done!
Danny

[Yorkshire_Jon]

When we put in split charge systems we use 35mm^2 between batteries.

The bigger the cable, the less resistance you have = better. Add into the scenario voltage drop - you will have several metres of cable between your battery box and trailer battery so you need to consider voltage drop.

I would expect to see 35mm^2 cable running back to the anderson plug at the rear of the vehicle and onwards to the trailer as a minimum, maybe even 50mm^2.

As for Anderson plugs, there are different sizes over here, a small one, a 175A and a 375A one. These are continuous power ratings and the 175A one would be more than enough for you.

[fraser130]

The way I see it here, the main culprit is your 3 way fridge, these genrally draw around 15amps on 12 volts, so no matter (to a point) what cable you use your camper battery is at a huge disadvantage as this load will always pull the voltage down a bit. Have you thought about something like an "Arrid" charger unit to put in the camper for it's battery? These actually can take a voltage as low as 8 volts (I think) and step it up to provide up to 25amps to charge the battery. The other (and cheaper) option would be to run 2 more cables all the way from your dual battery controller to your camper battery so the voltage drop caused by your fridge is only affecting the fridge voltage.
Or you could run the fridge on gas all the time.

Fraser

[Captain_Rightfoot]

The way I see it here, the main culprit is your 3 way fridge, these genrally draw around 15amps on 12 volts, so no matter (to a point) what cable you use your camper battery is at a huge disadvantage as this load will always pull the voltage down a bit. Have you thought about something like an "Arrid" charger unit to put in the camper for it's battery? These actually can take a voltage as low as 8 volts (I think) and step it up to provide up to 25amps to charge the battery. The other (and cheaper) option would be to run 2 more cables all the way from your dual battery controller to your camper battery so the voltage drop caused by your fridge is only affecting the fridge voltage.
Or you could run the fridge on gas all the time.

Fraser
15 AMPS!!! WOW.

A 40l engel uses 2.5 peak and that has proven enough to keep a family of 4 fed for at least 2 weeks. I think people get a bit carried away with refrigeration. :eek:

[drivesafe]

As for Anderson plugs, there are different sizes over here, a small one, a 175A and a 375A one. These are continuous power ratings and the 175A one would be more than enough for you.

Hi VentureOverland, why on earth would you want to use anything bigger than 50 amp Anderson plugs.

As far as cable goes, bigger is better but as posted, the advantages of thicker cable starts to be undermined by cost and handling size for what is usually only a minimal reduction in voltage drop and then only in cases of where the auxiliary battery is very low but the use of large size Anderson plugs is just a waste of money.

The bigger cable size will still not allow anywhere near 175amps to be carried because you would need to have an alternator of at least 200 amps capacity to provide anywhere near that sort of current.

Furthermore, even with a low auxiliary battery and the fridge running, it is highly unlikely that the set up could pull much over 50 amps at any time and as 50 amp Anderson plugs can take short bursts of up 180 amps, why go to bigger plugs.

Last but not least, I don’t know what the RV industries choice is in Britain but here, Grey 50 amp Anderson plugs are now pretty well the RV industry's standard for connecting battery cables between the tow vehicle and a caravan, camper trailer or float.

So using 50 amp Anderson plugs will not only meet wardy1’s needs but will keep his set up standard.

Cheers.

[fraser130]

Yes I know Captain!
3 way fridges are REALLY heavy on the current as they use a heating element in place of the gas flame when running on electricity. They are very inefficient on 12v, but are great on Gas (if it's not too hot) I don't think they even have a thermostat wired in to the 12v circuit. Really only to be used while the car is running.

Fraser

[wardy1]

Thanks guys. Captain Rightfoot, I run 2 fridges, one is a Waeco 50 ltr and then the 3 way in the camper. I find this provides a level of flexibilty in that the 3 way will provide 'cooling' while I can set the Waeco to freeze when required.
It is impossible to run any fridge on gas all the time as the flame will not remain lit when you are on the move, there would be a significant fire risk involved here also as the flame vents through a small flue which could in turn, turn the camper into a mobile bonfire!
I'll be upgrading the cable etc some time very soon:).

[Yorkshire_Jon]

I think we may have an inter-continental clash in descriptions here...

Of course a fridge and a few bits and bobs wont pull more than 50A. We rate the plugs at there max peak loading and not constant load rating (gray = 175A)... I therefore suspect that we are talking about the same plug!

[drivesafe]

Overland, I think we must be talking about two different types of plugs.

Anderson 50 amp plugs are rated at 50 amps continuos load with a surge load of up to 230 amps for around 1 second.

The colour actually has nothing to do with the current carrying capacity of any of their load ranges.

The colour is used to distinguish between different voltages and a plug of one colour is keyed so that it can not be connected to a plug of another colour ( voltage ).

Yellow = 12v

Orange = 18v

Red = 24v

Grey = 36v

Blue = 48

Green = 72v

For some unknown reason, here in Australia, we have adopted Grey as the RV industry’s standard for 12v use, while Red is commonly used for 24v.

[Redback]

Thanks guys. Captain Rightfoot, I run 2 fridges, one is a Waeco 50 ltr and then the 3 way in the camper. I find this provides a level of flexibilty in that the 3 way will provide 'cooling' while I can set the Waeco to freeze when required.
It is impossible to run any fridge on gas all the time as the flame will not remain lit when you are on the move, there would be a significant fire risk involved here also as the flame vents through a small flue which could in turn, turn the camper into a mobile bonfire!
I'll be upgrading the cable etc some time very soon:).

I have the same setup, i use a 20 watt solar panel too keep the battery in the camper topped up, i run the 3 way fridge off the car on 12volt while travelling and gas while camped.

I only run lights and a 12volt water pump in the camper, so i don't need much to keep the camper battery topped up while camped and the 12volt fridge is in the car running through Drivesafes SC40 dual battery controller (excellent bit of gear)

I have 6mm wire (that's the wire diameter not the wire and insulation combined) from the second battery in the car too a 50A Anderson plug and 6mm wire running to an Arrid smart charger in the camper too keep things charged while travelling, the wire is recommended for this sort of setup, drivesafe has it in stock if you want the correct stuff.

Baz.

[BradM]

I believe the altenator on the Disco II TD5 is 120 amp Nippon Denso. 15 amps being sucked by a 3 way fridge still leaves 105 amps to play with.

I have a 1000 cca catapiller battery as main, 60 amp deep cycle as auxillary joined together by starter motor cabling (including earth) from the wreckers through a 150 amp solenoid with zener diode built into it so it will not fire uless the voltage on the main side is higher than the auxillary. (Had a pirana isolator but it died)

I have a 50 amp hot wire which goes to the rear 12 socket from the aux which I run a 40l engle plus 70l engle impersonator fridge when travelling. Another 75 amp hot wire runs from the aux to a 50 amp anderson plug which charges 2 x100 amp deep cycle batteries in the caravan and powers the 12 volt heater in the Dometic 150 litre 3 way fridge when travelling. This fridge has a separate freezer in it which will freeze items or keep them frozen while travelling. The fridge is towards the back of my 21.5 foot van.

At night I have run all of the above with high beam, 4 spotlights on, rear lights plus van lights. The batteries have never gone flat and no problems down the back with the 3 way fridge.

The secret is the cable diameter and the terminating lugs as drivesafe has stated. Electrons travel mostly on the outside of the cable. Thicker the cable, the more electrons you get to the end allowing you to utilise the 120 amps available.

Regards,
BradM

[jik22]

related question Tim....not to steal the direction of the thread starter...


is it possible to go too big with the wire dimentions? reason being, I've got a roll of 50mm2 double insulated welding wire running around here somewhere - could I use that for charging a second battery?

Electrically, it can't ever be too big, but you do have to worry about the physical aspects of being able to run it where you want, and terminate it with something properly.