This question is a continuation of my previous question : What is the best way to combine multiple batteries (flooded lead acid)?
I have a battery bank of four 150 Ah 12 V flooded lead acid batteries connected in series and then parallel to achieve 24V 300 AH capacity. The batteries are charged by solar panels in the day and used to power connected load of approx 350 Watts at 230 V AC, through a 1.5 KVA 24 V inverter. The batteries are charged to 25.8 V by evening.
The inverter usually trips after about 8 hours of operation due to low battery. My problem is that at the time of tripping, the voltage in the (both) batteries to which the negative terminal of the inverter connected is 8.5V and that of the batteries where positive terminal is connected is 12.5 V. The inverter trip at 10.5 V which is the average of both values. The cables interconnecting batteries are of same size. I tested various combinations to see whether any particular battery is causing the drop but not found any thing abnormal. I Think this is highly abnormal. How can voltage of a 12 V battery can go as low as 8.5V ? The batteries where the positive of inverter is connected are seem to be in full power even as the inverter trips.why no power is drawn from the positive connected batteries ? What may be causing this sharp drop ?. How can I prevent such sharp drop in these batteries?.