Don't have my references handy so over to you guys please. If you have a good and bad 6 in series will the bad one ruin the good one? (Where the combo still acts ok as a 12 and is working ok for discharging and recharging)I know about the parallel situation where one drags down the other etc. But what about in series?Actual situation-- six-year old pair of 6s. When "full" one has three cells just in the green and the other has the middle cell just in the green but the outer two are in the red on the hydrometer.Is it just like a single 12 with six cells in series with two low cells?If the bad one won't ruin the good one, is it safe to add two more old 6s (both good) to have four in series/parallel? Will the pair with the bad one ruin the good pair it is in parallel with?If so, is this ruination a slow process --months? or fast--weeks?Thanks

When I had my bad interconnect cable the low SG 6V was continuously pulling amps from the Iota. Not much amps as they were on float but still pulling. It didn't seem to have much effect on the high SG 6 as it was only a little lower in SG than baseline. That could've been because I caught it early. Long term might have been different.

Hi BFL13,No the series connection will not "ruin" the other six volt jar--but capacity will be limited to what ever the worst "bad" cell can produce.You might try getting "fancy" and equalizing just the one cell by using a probe and a 2 volt charging current.Adding another series string won't help and would drag the "good" sixes down in capacity to what ever the worst cell does.

The capacity of the combo now with the one bad battery has not been measured. It will accept draws of over 100amps to run a microwave or toaster. When resting at 12.6 it will hold at 11.5 for two minutes with the microwave on, which seems fairly sturdy for a bad combo IMO. (U-2200s)Based on that, the owner is not going to be panicked into buying new batts just yet. I have advised him (he agrees) to try to last until end September when the trailer will be stored until next April. If he can hang on, then he can buy two or four new 6s next April and have no batts to maintain all winter, tossing these in October.The question really is what are his prospects with the good and bad 6s he has now? Three months to go. Does it happen that fast?(Back up plan is I can lend him a T-1275 or two to get him by if it all goes to poop.)

The bad battery, will limit the draw through both batteriesAnd will limit the amount of rechargeTotal capacity will be less than normalAnd the good battery will be slowly made worse, because of improper/Low recharge

Think about the issue with individual 2V cells. Parallel and series wiring attributes stay the same. Many of your 2V cells are already connected in series.

Series vs Parallel on Good and Bad Battery Combo?

14 Replies

MrWizard
Moderator
Jun 25, 2014
The bad battery, will limit the draw through both batteries
And will limit the amount of recharge
Total capacity will be less than normal
And the good battery will be slowly made worse, because of improper/Low recharge
BFL13
Explorer II
Jun 25, 2014
The capacity of the combo now with the one bad battery has not been measured. It will accept draws of over 100amps to run a microwave or toaster. When resting at 12.6 it will hold at 11.5 for two minutes with the microwave on, which seems fairly sturdy for a bad combo IMO. (U-2200s)

Based on that, the owner is not going to be panicked into buying new batts just yet. I have advised him (he agrees) to try to last until end September when the trailer will be stored until next April. If he can hang on, then he can buy two or four new 6s next April and have no batts to maintain all winter, tossing these in October.

The question really is what are his prospects with the good and bad 6s he has now? Three months to go. Does it happen that fast?

(Back up plan is I can lend him a T-1275 or two to get him by if it all goes to poop.)
pianotuna
Nomad III
Jun 25, 2014
Hi BFL13,

No the series connection will not "ruin" the other six volt jar--but capacity will be limited to what ever the worst "bad" cell can produce.

You might try getting "fancy" and equalizing just the one cell by using a probe and a 2 volt charging current.

Adding another series string won't help and would drag the "good" sixes down in capacity to what ever the worst cell does.
mena661
Explorer
Jun 25, 2014
When I had my bad interconnect cable the low SG 6V was continuously pulling amps from the Iota. Not much amps as they were on float but still pulling. It didn't seem to have much effect on the high SG 6 as it was only a little lower in SG than baseline. That could've been because I caught it early. Long term might have been different.

Forum Discussion

Series vs Parallel on Good and Bad Battery Combo?

14 Replies

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