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I have 4 Rolls 500 batteries in series. They are 11 years old, and apart from being a bit thirsty, still do the job. J read somewhere that it is a good idea to end to end them occasionally. I never have, partly because they way a ton and not brilliantly accessible. Any ideas?
Thanks,

Mike

Absolutely. Swap the inners and outers. The cells closest the cables work the hardest and consume the most water hence deteriorate fastest.
I sort them by open circuit voltage after a day's rest having charged the cells to 1.275 specific gravity per. Strong outside, weak inside.

ok, will do thanks.

I am confused.

I can understand why end for ending would help batteries in parallel when the cable path to/from each battery is not exactly the same. However, for batteries in series, the current through each battery is the same.

Do you have 4*6v batteries to give you 24v?

Indeed I do, and to be honest, the end batteries do not seem to drink more water than the others. Maybe I don't have to disconnect and turn around. here's hoping!

John_S wrote: ↑Wed Jan 15, 2025 9:56 am I am confused.

I can understand why end for ending would help batteries in parallel when the cable path to/from each battery is not exactly the same. However, for batteries in series, the current through each battery is the same.

Do you have 4*6v batteries to give you 24v?

The current is the same but the voltage across each cell is not because of the voltage drops in the interconnecting cables which increases the further towards the centre cells on both charging and discharging. Thus the outer batteries work harder and the inner ones less in terms of power (I x V). The difference is small but can make a difference over the years.

I thought the OP just confirmed that they're in series.

The cables transmit heat into the cells too making them gas more. That said if it's a tight pack like a forklift bath then the centre cells will get hottest from lack of convection and being surrounded by other exothermic cells.

Yes, they are in series. They are big batteries, 1156 AH each battery, connected by thick wires. They don't work too hard, we draw about 4 kwh a day. max draw is 1 kw from the washing machine and max charge from the panels or generator is 70 amps 24v dc.

I suppose if you EQ them and they all have identical specific gravities and water consumption there's nothing to fix.

I rotate my lead every 2 years.