Low Specific Gravity Issue in Flooded Lead Acid Battery

[Mohsin Ali]

Hello Everyone,
I purchased a 12volts Flooded Lead Acid Battery last month having 140Mah capacity and installed in my off grid solar system, a brief overview of which is here,
1) MPPT Solar Charge Controller 80A
2) 3 X 180watt Solar Panel & 1 X 330 watt Solar panel connected in Series
3) Pure sivewave Inverter 1500 watts

The manual came with the battery suggested Cutoff Voltage setting of 14.4 volts and low voltage cuttoff of 11.5 volts. But I set cutoff voltage of 14.1 volts in the SCC and discharged battery upto 11.6 volts. After a month of use I notice decline in backup time so checked the Specific gravity which came out to be 1200 which is low as per standard. Now what should I do to get back the normal Specific Gravity of 1250 .
Thanks in Advance

 

[DIYrich]

1200 when fully charged? Did you measure each cell? Can you remove the top, or is it sealed? If sealed, not much you can do.

 

[Mohsin Ali]

1200 when fully charged? Did you measure each cell? Can you remove the top, or is it sealed? If sealed, not much you can do.

Yes I removed caps and checked each cell separately, almost all have a gravity in between 1200 - 1225

 

[wpns]

Why charge to 14.1 instead of 14.4? Might just need a good equalizing charge.

 

[Mohsin Ali]

Why charge to 14.1 instead of 14.4? Might just need a good equalizing charge.

To avoid overcharging, I lowered the bulk charging voltage
Can you please guide how to equalize charge with an MPPT solar charger having no equalization function?

 

[time2roll]

Set the charge voltage to 14.8 and the minimum s/b 12.0 - 12.1 volts. Do this for 2 to 4 weeks then drop back to 14.4 volts.

To equalize this would be closer to 15.5 volts for an hour.

Have you checked the water level?

Also that absorption time to hold charging voltage s/b 90 - 120 minutes maybe more.

There is a good chance the battery is partially sulfated and may never return to full capacity.

 

[OzSolar]

To avoid overcharging, I lowered the bulk charging voltage
Can you please guide how to equalize charge with an MPPT solar charger having no equalization function?

Chronically undercharging flooded lead acid batteries is one of the best ways to kill them. The low SG you are seeing demonstrates that.

Disconnect all the loads if you can and charge the battery to at at least 2.55 Volts per cell (~15.5 V) until the SG of all the cells is up to 1275. One or more the cells may lag behind the others, hence the reason this is called equalization charge.

Check out the link in my signature line for all you need to know.

Only add enough water to cover top of the plates. DO NOT TOP THEM OFF or as they start to recover they will could "boil over".

Flooded lead acid batteries are robust and when this situation is caught early the battery is going to be fine.