6 Volt Battery Charging

[Great Horned Owl]

I just bought two 6 volt, 232 Ah, golf cart batteries. Initially, one of them was fairly well charged (6.38 V), while the other was not (6.04 V).

Since they are charging in series, the same current will flow into both of them. The one that started lower will never catch up, and will never get fully charged.

For reasons that I do not completely understand, the voltage difference between the two increased after several hours on the charger. At one point, I measured 6.59 V and 7.18 V. BTW, the manufacturer suggests bulk mode charging up to 7.75 V

I took took them off of the charger and hooked a 15 ohm load across the one with higher voltage until they were approximately the same. Then, I removed the load and connected the batteries in parallel to make sure that they were precisely the same. Next, I'll put them back on the charger in series.

Will this kind of imbalance keep happening? If so, is there a simpler solution, or am I worrying about nothing?

Joel

[Herk7769]

What comes to mind is that a plate might be damaged in one.
Identical batteries should charge identically in a series, I would think.
I would contact the manufacturer.

[RPAspey]

If the batteries are the same, including age, then the charge rate and capacity will be very, very close.


there may not be a problem just yet. 1-leave the batteries connected in series. 2-run an equalize charge on them for about 2-4 hours. 3-check cell voltages again. my guess is that voltages will remain similar.

I run the equalize function once a month or so. keeps the batteries from getting sulfated and prevents mismatched voltages.

[Great Horned Owl]

Thanks guys for your responses. It turns out to be a non-problem.

I put them back on thc charger for another 4 hours to equalize them, and they settled at a constant 7.21V and 7.51V. This was a lot closer.

After sitting overnight without being on the charger, they are now both reading 6.38V. Problem gone. The equalizing did the trick.

Joel