Batteries

Ahir

Hi,
I am using six CosLight (6-FGM-150X/H)  12 volts batteries for 24 volts system.The batteries were all ok till i closed the whole system after full charge, remove the terminal for two months, after 2 months all the batteries were at approx 12.30 volts current. but now i am experiencing the issue that zero load following is the condition
Battery #
01 at 12.60
02 at 12.30

03 at 12.65
04 at 12.33

05 at 12.55
06 at 12.30

When putting load of 1.75 ampare AC after some time the condition becomes
Battery # 
01 at 12.40
02 at 10.65
03 at 12.40
04 at 10.55
05 at 12.38
06 at 10.65

if charging is resumed after some time batteries went on float. 
How this situation can be handled?
Regards,

inetdog

If these were FLA batteries the simplest thing to do would be to fully charge the bank to Float and then put it on an Equalize cycle until the resting battery voltages were again equal.
But since it is a sealed, AGM, battery you must not use the Equalize cycle of a standard Charge Controller (CC). If you can get specific recommendations from the manufacturer an extended Absorb or mild Equalize period might be possible, but you would need to know the exact voltage limits and monitor the voltage and temperature of each individual battery.

In your case, however, I would start by disconnecting the batteries and charging each one separately with a 12V charger (with correct voltage limits.)

What has apparently happened is that some of your batteries have a higher self discharge current than the others and so have gotten out of balance, in terms of state of charge, with the other batteries in the bank.
If you cannot get a suitable 12V charger, rearrange the batteries so that the two batteries in each series string start out roughly equal in voltage.
Do NOT reconnect the series strings in parallel until you have gotten the string voltages matched by charging the strings individually.
Also make sure that during the Bulk stage of charge the current to each string does not go above C/6 where C is the listed AH capacity of the battery.