In charging my twin group 27 deep cycle lead acid batteries wired together to produce 12 volts (called series?) if I charge at 15 amps am I really charging both at 7.5 amps? Or are they both charging at 15 amps? BTW I got an astonishing nine years out of my last set of Costco interstate batteries. I had a load test performed on the deceased and one rated good, the other was toast as I mistakenly set the smart charger to charge at 40 amps.

What does the battery manufacturer recommend for charging voltage?

That is wired in parallel.And yes,7,5 amps per battery.And 40 amp setting won't hurt 2 27 DC batteries

Are you sure you have group 27 batteries? Those are 12 volt batteries, so two of them wired in parallel is the only way to properly connect them. That is, positive to positive and negative to negative. This connection method provides 12 volts, but gives you the amp hour capacity of both batteries combined, so about 105 amp hours x2 = 210 amp hours, 12 volt.If you had 2 x 6 volt golf cart batteries, you must connect them in series (one positive terminal going to other battery's negative terminal, the remaining terminal of each battery being pos and neg. Their voltages combine to become 12v, but the amp hours will only be that of a single battery (220 amp hours).Google search battery series / parallel connections for a good picture or two.To answer your question, yes if you have a parallel battery setup each battery will see about half the rated current of the charger. If you had a series system with 6v golf cart batteries, then the current would be the rated current through both.

Series. Daisy chain. What climbs from one end, comes off the other end. 15A it is. What puzzle?

Oasisbob wrote:In charging my twin group 27 deep cycle lead acid batteries wired together to produce 12 volts (called series?) if I charge at 15 amps am I really charging both at 7.5 amps? Or are they both charging at 15 amps? BTW I got an astonishing nine years out of my last set of Costco interstate batteries. I had a load test performed on the deceased and one rated good, the other was toast as I mistakenly set the smart charger to charge at 40 amps.The answer is "depends" in a perfect world both would receive 7.50amps....... The way the batteries are wired play a large role on charge and discharge behavior. Here is some homework if you are interested.Good stuff here

BATTERY CHARGING PUZZLE? | Good Sam Community

wnjj
Explorer II
Apr 26, 2018
Almot wrote:
Oasisbob wrote:
I have my two group 27 batteries wired together positive to positive and negative to negative.

This is parallel. Current is split.

Yep, and the reason it’s called parallel is that a schematic diagram, much like the actual wiring red31 showed, has the positive and negative wiring running parallel to each other.
wa8yxm
Explorer III
Apr 26, 2018
Group 27s wired to produce 12 volt would be in PARALLEL and yes if your charger is putting out 15 amps. each battery is likely eating 7.5.

GC-2's are six volt. to get them to make 12 you put 2 in series.

Batteies wired in parallel add capacity (you have just under 200 amp hours at the /20 rate adn can use about 40-45 of them safely)

Batteries wired in Series you add VOLTAGE.. My DEKA G-20's are 230 amp hours and I can use 115 of those safely.

BIG time differnece.
ChuckSteed
Explorer
Apr 26, 2018
If they are flooded group 27 batteries I’d routinely chec’ the specific gravity of each cell..
Gives you a good idea of the real charge and health state of t(e battery...
grizzzman
Explorer
Apr 26, 2018
If concerned there are balancers that work at keeping the batteries at the same voltage.
garyemunson
Explorer II
Apr 26, 2018
Parallel connecting batteries is always problematic. As they get older and one battery gets weaker, the 'better' battery ends up working to try to bring the weaker battery's voltage up. Series connections are generally a better idea with batteries to prolong their life. Why a pair of 6 volts hooked up in series to provide 12 volts always seem to last longer.
Oasisbob
Explorer
Apr 26, 2018
You folks are great. A thousand thanks. You are what makes this forum great
2oldman
Explorer II
Apr 26, 2018
parallel
Almot
Explorer III
Apr 26, 2018
Oasisbob wrote:
I have my two group 27 batteries wired together positive to positive and negative to negative.

This is parallel. Current is split.
Oasisbob
Explorer
Apr 26, 2018
Sorry sports fans. Perhaps my terminology is wrong. I have my two group 27 batteries wired together positive to positive and negative to negative. Volt meter reads 12 volts going to my trailer. I am now confused. Is this Series like I thought or is this called paralell? And I am understanding the charging amps gets split between the two? Is that right?
Almot
Explorer III
Apr 26, 2018
2*6V series would get 15A per each 6V battery, 2*12V parallel would get 7.5A per each 12V battery.

He never clarified what his 12V bank made of: 2*6V or 2*12V, - assuming this is really 12V bank.

Page 2 and counting :)

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