I'am using two serial 12V 122Ah AGM batteries to get 24V. I'am measuring the Mid-Point Voltage via a SmartShunt and a Multimeter.
Between the Batteries there is a thirdparty balancer which measures the voltage of each battery and charges the one with less voltage with up to 2A to equalize.
Also the Battery are AGM of the type "China" :)
+ ---[BAT1]---[BAT2]---- -
I'am charging the batteries with a victron IUoU Charger which delivers maximum 15A
Absorption Voltage is set to 29,4V, compensated by 60mV/degrees measured at the surface of BAT1
so far so easy.
Usually Absorbtion starts at a tail current of around 10A and from around 6-8A tail current (approx. 95% SOC) the Mid-Point deviation reaches 4% or more.
Today: at 94%, 4A Tail Current BAT2 got 15,3V out of the 29,6V feed. For testing reason, the balancer has been removed.
The Age of the batteries is 1,5 Years, i never discharge it more than 70%SOC.
What could be the issue here, higher inner resistance of one Battery? is there a way to mitigate that?