Mid-point voltage deviation

[crookedspoon]

Hi all,

I have 2 PowerQueen 25.6V 100Ah connected in series. They're being charged with a Victron Smart Solar 150/35 and a Hoymiles Inverter is taking energy from it. Lately, when reaching the absorption phase of charging, my Victron smartshunt has been throwing alarms to inform me the mid-point voltage deviation is too high.

1 Battery is 4 months older than the other, and has some 30 cycles more than the other.

Using a multimeter, I noticed the older battery seems full (with a higher voltage) where the newer on is still charging (lower voltage)

Connections are tight. Cables are short, 6mm PV-cables.

Yesterday, I had both batteries connected in parallel over night as to 'balance' them - to no further avail.

Any course of action here? How else should I / could I balance these batteries?
How can I know if one of the batteries is defect?
What to do to solve the voltage deviation problem?

thanks for you insights!

all the best,
shiny

 

[sunshine_eggo]

Did you fully charge each battery to 14.4V individually and then again in parallel before wiring in series?

If not, that may be needed.

There are balancers that seek to keep the 12V at equal voltage:

https://www.amazon.com/dp/B09CYMXJRR