Battery wiring wrong?

[Tony 260DS]

Hi,
See picture. Service added a second battery in parallel for us and connected the RV pos and neg to ONE battery. 90% of what I’ve read says the pos and neg should be connected to separate batteries, for charging balance and efficiency. I have read a few places saying it doesn’t really matter, the difference is negligible.

And, if I needed to charge the batteries where would I attach the charger pos neg clamps in the current configuration? To the one battery with the rv connection?

Help with this?
Thank you.

[TitanMike]

Unless you are discharging and charging at HIGH current levels the difference IS negligible.

At the discharge/charge levels present in MOST RV's when using batteries, worrying about how the batteries are connected is like "picking fly poop out of ground pepper".

As long as 12 volt batteries are connected in parallel and 6 volt batteries are connected in series to produce 12 volts, that's what is important.

Use the largest wire size that's practical to connect batteries in parallel and all is good.

[Tony 260DS]

Originally Posted by TitanMike

Unless you are discharging and charging at HIGH current levels the difference IS negligible.

At the discharge/charge levels present in MOST RV's when using batteries, worrying about how the batteries are connected is like "picking fly poop out of ground pepper".

As long as 12 volt batteries are connected in parallel and 6 volt batteries are connected in series to produce 12 volts, that's what is important.

Use the largest wire size that's practical to connect batteries in parallel and all is good.

Thanks for the feedback and thanks for the LOL on that quote.

[rsdata]

Originally Posted by Tony 260DS

Hi,
See picture. Service added a second battery in parallel for us and connected the RV pos and neg to ONE battery. 90% of what I’ve read says the pos and neg should be connected to separate batteries, for charging balance and efficiency. I have read a few places saying it doesn’t really matter, the difference is negligible.

And, if I needed to charge the batteries where would I attach the charger pos neg clamps in the current configuration? To the one battery with the rv connection?

Help with this?
Thank you.

although it is too late to do anything about it now, for future reference two batteries in parallel should be the exact same make and age... as you now have it the weakest and/or oldest battery will always pull the better of the two batteries down ... to whatever level of performance is the lowest common denominator

when charging always hook POS to POS and NEG to NEG... any battery post in any configuration will be the same according to the wiring of parallel batteries...

check this out
https://batteryguy.com/kb/knowledge-...s-in-parallel/

[nvs4602]

The best way to wire them is to put the negative lead on 1 battery athe possible lead wire on the 2nd battery. Then both batteries will charge at the same rate. That will compensate for any resistance in wiring between the 2 batteries.

[TowPro]

what you got is fine, we are not wiring rocket ships here, its an RV. There is so little resistance in those hookup wires it don't matter.

The time you see a wire on each battery is when they hook Two 6 volt batters (golf cart) up in series to make 12V.

[eric1514]

If it bothers you, and it would bother me, move the positive cable to the other battery.

[Flybob]

The fact that you have differences in batteries is more significant than the wiring scheme, but for an RV you will likely not see any impact.

[eric1514]

And perhaps moving the cable would help mitigate those differences.

[Chuck_S]

It's not that hard to connect correctly but it may take 5 minutes...



-- Chuck

[5picker]

Originally Posted by TitanMike

Unless you are discharging and charging at HIGH current levels the difference IS negligible.

At the discharge/charge levels present in MOST RV's when using batteries, worrying about how the batteries are connected is like "picking fly poop out of ground pepper".

As long as 12 volt batteries are connected in parallel and 6 volt batteries are connected in series to produce 12 volts, that's what is important.

Use the largest wire size that's practical to connect batteries in parallel and all is good.

X2

The voltage/amperage loss in that less than one foot of heavy battery cable is negligible and you will not see a difference in performance or life of the battery.(ies)

[TitanMike]

Originally Posted by TowPro

what you got is fine, we are not wiring rocket ships here, its an RV. There is so little resistance in those hookup wires it don't matter.

The time you see a wire on each battery is when they hook Two 6 volt batters (golf cart) up in series to make 12V.

Something that's hard for many to grasp because they saw a wiring diagram on an RV Blog, etc, etc, etc.

When using a heavy gauge wire (the larger the better) as you said, there is so little resistance it doesn't matter.

Same for worrying about equal length jumper wires, etc.

Then again, if one is wiring batteries with SMALL wires, then it might make a difference but in that case there are other issues far more important. For charging, when the batteries approach full charge the current drops and they will all reach the same voltage/state of charge, even if wired with 16 ga wire connected on the "same side".

[eric1514]

Originally Posted by TitanMike

Something that's hard for many to grasp because they saw a wiring diagram on an RV Blog, etc, etc, etc.

When using a heavy gauge wire (the larger the better) as you said, there is so little resistance it doesn't matter.

Same for worrying about equal length jumper wires, etc.

Then again, if one is wiring batteries with SMALL wires, then it might make a difference but in that case there are other issues far more important. For charging, when the batteries approach full charge the current drops and they will all reach the same voltage/state of charge, even if wired with 16 ga wire connected on the "same side".

All true, but we know that moving that positive cable to the other battery is the correct thing to do whether it’s theoretical or not, and since it would take 5 minutes to do including stopping for a beer break, why not just go ahead a get it done.

[NMWildcat]

Originally Posted by eric1514

All true, but we know that moving that positive cable to the other battery is the correct thing to do whether it’s theoretical or not, and since it would take 5 minutes to do including stopping for a beer break, why not just go ahead a get it done.

Because it really does NOT matter in this case. The only change would be to make you feel better...

[itat]

Originally Posted by eric1514

If it bothers you, and it would bother me, move the positive cable to the other battery.

Me, too. I’m a bit of a perfectionist and it would bother me even though, as others said, it doesn’t make much difference in performance for the OP’s situation. I like to form good habits and do it the proper way. Heck, I’d be bothered by having two different-aged 12V batteries.

[TitanMike]

Originally Posted by eric1514

All true, but we know that moving that positive cable to the other battery is the correct thing to do whether it’s theoretical or not, and since it would take 5 minutes to do including stopping for a beer break, why not just go ahead a get it done.

I agree that one could do it if they want but the latin term for this is "de minimis - lacking significance or importance: so minor as to merit disregard"

Those that are insistent that this is the ONLY proper way overlook the fact that sometimes the extra length of wire necessary merely contributes to the "rat's nest' effect and it's contribution to performance is 'de minimis'.

FWIW, if you have a large number of batteries connected into a large bank like in a Fork Lift, Off Grid Solar System, or maybe a 'Diesel Electric Submarine, where discharge and charging currents are in the hundreds of amperes, then wiring so electrical paths on the positive and negative sides of batteries are equal length (translated into equal resistance on each side) THAT's when this wiring strategy becomes important.

With half a dozen batteries in an RV, being charged with a 50-60 amp converter charger, way too much over-thought going into it.

More important is having matched batteries and charging for more than "a couple hours in the morning and a couple hours in the evening".