Battery wire question

Ideally, batteries shold be "balanced" - loads (or alternator) should use Pos from one battery, and Neg - from another one.

If they dropped each Neg directly to the frame - I don't know how to balance them, other than running a separate #6 Neg wire from the farthest battery to loads/alternator. Maybe braniacs here will suggest something better ;)

With ours I put the second battery in the front left corner of the truck bed ahead of the wheel well. I cut a hole in the camper lower side up there and installed a plastic "cable hatch".

I parallel linked the two batteries through the cable hatch so they were close together, and I was able to also pass a wire out to the second battery for the load/charge to its neg post, while the inside battery had the pos load/charge wire.

If they are that close and with low amps (under 20 say) #6 should be fine. With an inverter to run 120v things you will want #4 links even though they will be shorter than now.

When loading the camper, you get it in past the wheel well, then pass the wires so you can still see the second battery, then slide it in all the way. VV unloading.

#6 is fine. Since they are rarely relied upon I would leave it as is. Yes it would be better to balance them.

Best bet is to be fanatical about clean bright connections...

Years ago researchers ask 3 groups of men "Briefs or Boxers"

The young men answered briefs
The middle age boxers
The seniors... "Depends"

And well. the Seniors have the wisdom of their years.. It Depends.

It depends on how much power you use at peak times.
If you are only have a few lights, and a water pump and control power for Fridge and other appliances.. 6Ga is more than enough 10 might be enough.

IF you charge at 80 amps, as I do and can draw as much as 200 (2000 watt inverter) 6ga is called a "FUSE".

So it depends.

On a trailer.. with no inverter. Likely ok.


Personally if I were adding I'd use 4GA. not because it is better, but because I can buy 4GA in assorted lengths at most any auto parts store with the needed lugs already attached cheaper than I can make it up in the shop.

I use copper stranded welding cable myself, with crimp on, solid copper Tweco lugs. Welding cable is available at any welding shop by the foot so you buy only what you need.

It would be good to know if the batteries are 12v, 2 in parallel, or 6v, 2 in series. It would also be good to know if the batteries are charged by the engine or do you have a converter?

I'm not familiar with truck campers but I suspect the charging current would be the big current. Fortunately the wires are fairly short.

When I replaced my converter I used #4 wire to reduce the voltage drop and give faster charging.

Neok,

None of the answer you got are really wrong, but would you like an real solid answer??

It won't matter.

Two 12V batteries that are so far apart will never balance anyway. It will simply be impossible to charge or discharge both the same amount. Not just because of the wire between them, but also because they:
* Were not matched to begin with,
* Will always be at different temperatures,
* Will get different levels of care,
* They are going to charge and discharge differently do to the resistance between the jar and the activity.

Parallel batteries are very hard to keep matched. There is just nothing that can be done about that. When installing paralleled banks (I never like to) I used a special instrument to balance the connecting cables to 0.01 ohms. If the owner called and said he had lost capacity, I would tell him to clean the cables ends and recharge. Or I could come and do that on his dime.

Matt

Matt_Colie wrote:
Neok,

I used a special instrument to balance the connecting cables to 0.01 ohms.

Matt

mind telling us what the special instrument is?

There may be another solution.Battery balancer
Good luck with your project!