Thread: Charging Deep Cycle in my camper

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.

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


Charging an aux battery in a trailer?
this may help,, or not, but its worth a read just for the banter--

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

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.

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?

Originally Posted by 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?

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

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

Drivesafe...

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

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.