Quick battery bank wiring questions

[lfhoward]

I have three 12 volt deep cycle batteries that will be connected together and live in a tongue box on my trailer (12 volt system).


The charge controllers (plug-in plus solar) and the rest of my electronics including the 1000 watt inverter live inside the trailer itself. Thus, I will need heavy gauge cables connecting the batteries to the inverter & distribution center inside the trailer.

I am familiar with the need to have the load cables connect to + and - on opposite ends of the battery bank to equalize the electrical draw across all three batteries and maximize their lifespan.

Quick Questions:

1) Do the wires from the battery charger need to connect to the battery bank at opposite ends for the same reason (equalizing the charge), or can they go to the middle battery terminals, for example?

2) Can the charger instead be hooked up to the same load cables as the inverter on the trailer (power distribution) side (to eliminate the need of running separate charging wires into the tongue box)?

I am not familiar with the pros and cons of wiring the charger to the load cables rather than the battery terminals themselves. Would there be an issue when solar charging and running the inverter at the same time, for example?

Thanks for clarifying these issues for me before I set up the tongue box wiring!
Lauren

[Gunguy05]

I am interested in the answer to your question as well.. but that's going to be some heavy weight on that tongue.. like over 200 lbs?

Any worries about tongue weight as far as the TV goes?

[lfhoward]

Those are good questions. The TV has a 500 lb tongue weight limit, but the batteries are 45 lbs each. If the trailer is 2000 lbs when I'm finished (it's a steel military trailer) and the tongue weight is approximately 10% of the trailer weight without batteries, that would add 200 lbs. So with batteries, we are looking at perhaps a 350 lb tongue weight?

[Shadow Catcher]

Generally converters and controllers play well together, I do not disconnect the controller when on shore power.
Since it is three batteries that means 12V batteries so wired in parallel. You need to have vents at the top of the tongue box as the batteries can vent hydrogen.
If the controller is going to be in the box with the batteries, you might want to consider it, keeping the wiring from controller to the battery bank short is a good idea, then ventilation is doubly important.

[Redneck Teepee]

http://www.gearseds.com/files/twobat_onechgr2.pdf Here is a diagram for charging in parallel

[H.A.]

[

[lfhoward]

H.A., Redneck Teepee, and Shadow Catcher, thanks for your informative answers. It is really going to simplify my wiring to have the battery charger and solar charge controller simply plug in to my BlueSea fuse panel with the correct amperage fuses than to run separate charging wires to the batteries with in-line fuse holders. Sweet.

The BlueSea fuse panel has 6 circuits. They will be:
1. Fantastic fan - 5A
2. Dome lights and reading lights - 5A
3. Power outlet (L) - 15A
4. Power outlet (R) - 15A
5. Solar charge controller - 10A
6. Battery charger - 20A

[lfhoward]

Generally converters and controllers play well together, I do not disconnect the controller when on shore power.
Since it is three batteries that means 12V batteries so wired in parallel. You need to have vents at the top of the tongue box as the batteries can vent hydrogen.
If the controller is going to be in the box with the batteries, you might want to consider it, keeping the wiring from controller to the battery bank short is a good idea, then ventilation is doubly important.

Can you recommend a good waterproof vent that can be installed on a battery box? I am open to ideas. Thanks!

[lrrowe]

I really struggled with this issue. For the battery box I bought which can hold four 6V batteries if I want I drilled a hole and forced fit a plastic plumbing fitting to a 1 1/4" hose I was able to finally locate in a Big Box Store. For the exit end, I did order a trailer fitting part and adapted it to the hose. In other words, it was a pain in the neck to construct.

If others do not post better and more informative replies to your question, I can go out and take photos for you and try to find the Brand names for the items used.

[H.A.]

Can you recommend a good waterproof vent that can be installed on a battery box? I am open to ideas. Thanks!

Were it mine, probably a plastic elbow of some kind.
Thats if I thought its was tight seal.

At any rate, I say holes in its bottom also.
1,Water is bound to get in & needs a drain.
2, if hydrogen needs to vent in quanity, it will go better with bottom venting too.
Further, excess hydrogen is developed, excess heat will be present as well what helps convecting an airflow.

If you are using flooded batteries, be prepared to see alot of corrosion on that shiny interior.