Parallel battery wiring error?

pthomas745 · October 2022

There have been some interesting battery installs popping up on FB in the last few days. Owners are asking about power usage, etc. They are asked for pictures of the battery. One the other day had the dealer "install and extra battery", so they just added another 80ah battery. But..without wiring it up. They just set it up in the tub next to the original!

This is the same type of install. The owners wanted a "dual battery" setup, so the dealer just supplied another 80AH battery. They owners are aware of the "too small battery and the 2 way fridge" issue, and have been driveway camping to test it out. But, they are complaining the batteries aren't lasting, even with "full sun". Finally got the Victron history pages, and the solar input has been only 30wh per day (not nearly enough). Of course, their battery is down to less than 50 percent. I asked for a picture of their battery wiring....and this is what they sent.

Image: https://us.v-cdn.net/5021717/uploads/editor/r7/iti12l325fez.jpg

It seems to me this needs to be cleaned up...but I honestly would just be guessing on the "right way". I can't tell which of the wiring harnesses are for the trailer and which one for the installed solar. The extra white "ground" wire on the right side battery just seems to be a bit off to me.

How should this really look? Or, is this correct?

techietab · October 2022

I don't see a wiring error. The battery terminals are connected in parallel correctly. The usual convention would be to attach positive and negative load connections at opposite 'ends' of the battery bank (e.g. positive on battery A, negative on battery B ), but things will still work if you wire as pictured above.

Personally, I'd move everything over to bus bars. Much easier to work with and supports better cable management.

Edited for clarity: load connections would be distributed to either end of the battery bank.

MuttonChops · October 2022

@pthomas745 ; The wiring doesn't look "that bad / messy". Dealership did as requested; just dropped in a second parallel connection 12V battery so they should have ~ 74Ahr of power available.

My view of the wiring is:
1. Factory Solar was moved to the added battery on left
2. Factory original wires, except solar, stayed on right battery.

Image: https://us.v-cdn.net/5021717/uploads/editor/bc/e2b6p4c31m1g.jpg

MuttonChops · October 2022

techietab said:
. . . battery terminals are connected in parallel correctly.

. . . The usual convention would be to attach positive and negative connections at opposite 'ends' of the battery bank (e.g. positive on battery A, negative on battery B ), . .

Edited *:58

@techietab; To be clear your comment on usual convention is confusing.

The Picture in your later post clarifies the words of your eariler post (at least for me).

Sharon_is_SAM · October 2022

@pthomas745 - a good lesson in "be careful what you wish for". It sounds like they are not aware of what they really need to begin with. Did you suggest they get two 6V batteries so they can have 225 Amphrs?

techietab · October 2022

Respectfully disagree with your assessment, @MuttonChops. The below is extremely typical in a 12v bank connected in parallel.

Whats The Difference Between Wiring Batteries in Series Vs Parallel

MuttonChops · October 2022

@techietab ; The picture clarifies what the earlier words confused (for me). Thank you.

pthomas745 · October 2022

Thanks for the responses and discussion. I guess I was more used to the "negative on one battery, positive on the other battery" wiring. This one looks a bit slapdash. For this owner, the solar does not "seem" to be charging. Does seem to be charging on shore power. I just wanted to eliminate a bad wiring setup before other discussions.

@Sharon_is_Sam I completely agree. The FB page has had a lot of new owners reporting the "too small battery" issue over the last year. New buyers don't exactly know what they are asking for, or they just get a bit overwhelmed with the choices. The two 80 amp hour batteries is "not bad" as an upgrade, and easy to do, at least. This owner is really practicing hard in the driveway, so I give them credit for that. I hope they can figure out their solar issues today.

techietab · October 2022

I wouldn't be especially concerned about the default solar panel not seeming to do much charging. The Victron controller will only start a charge cycle if the panel outputs +5v above the battery voltage, and that can be difficult to pull off during the fall in any but the most perfect sun conditions.

pthomas745 · October 2022

@techietab I understand what you mean, but their readouts are just too low (unless they are in Alaska, maybe!). I'm was mostly trying to eliminate the battery setup from the lack of solar input.

Parallel battery wiring error?

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