Hi, I have a few Lead Acid 55Ah 12V batteries holding it's voltage at 12.7V, but I've measured the capacity to about 20Ah. Is there a way to increase the capacity on these batteries?

 

simple answer is NO. Now you need to define how you came to the 20 AHr figure. Factory ratings are mostly "total depletion" points, or 11 volts or less under load for 12 volt battery. Discharges around 50%, which are considered normal and not deep discharge, make your 20 Ahr figure close to expected value

 

Buy new or larger batteries.

LA battery capacity decreases with time, especially if they are left undercharged, and over discharged, so just buying new ones of the same rating may be sufficient.

If the original batteries are too small, buy ones with more Ah...

 

If not sealed make sure the water level is where it should be.

If sealed or the level is fine then buy new ones.

 

simple answer is NO. Now you need to define how you came to the 20 AHr figure. Factory ratings are mostly "total depletion" points, or 11 volts or less under load for 12 volt battery. Discharges around 50%, which are considered normal and not deep discharge, make your 20 Ahr figure close to expected value

Its also worth remembering that manufacturers quote the Ah capacity over something like 10 or 20 hour discharge rate.

If you calculate a load to discharge a 55Ah battery in 1 hour - it'll be flat somewhat sooner.

 

Hhave you attempted to equalize the batteries and at least test the spec. gravity of the cells to see what's happening?

 

@kje
To get some extra life out of a battery, you can try this but it only works some times.

Empty the battery, rinse/flush with distilled water, refill with new battery acid (sulfuric acid at correct concentration). Charge.

If there is significant sulfated bridging or thick/hard sections of sulfate, or lead plates that are cracked or other damage, the battery has to be replaced.

If the batteries are new and you just want to increase the capacity of your existing batter, you will not find an improvement for each individual battery. You can add capacity by adding more batteries in parallel.

 

Once batteries have lost capacity, dump them, there will be more problems soon, total failure possibly.

 

@GopherT I would like to make a small correction about your post. Please take a look at the next link: http://blog.thesolarbiz.com/page/10/ It looks like not a good idea to connect batterys parallel. Or am i wrong? Btw, sorry for my poor English.

 

@GopherT I would like to make a small correction about your post. Please take a look at the next link: http://blog.thesolarbiz.com/page/10/ It looks like not a good idea to connect batterys parallel. Or am i wrong? Btw, sorry for my poor English.

You should use a charge balancing circuit to insure that you do not under-charge one or more batteries in a series-parallel configuration.

 

I tend to agree with GopherT.
The article points the problem out and leaves it to you to figure out the rest so it is somewhat misleading.
I don't think that because a magazine article states a problem that we are going to or should quit paralleling batteries, if the voltage is not what you want then ???
Charge the bank correctly and maintain it well and it should serve for the expected life of your system.