battery capacity

Thread Starter

petercl14

Joined Sep 29, 2012
3
I have been using deep cycle lead acid and ni-mh batteries and it has become quite clear to me now that a new battery needs to be used quite a few times before its capacity increases to a maximum. this capacity seems to be 50% or more from its new capacity.
for instance I have a new 6,800 mah ni-mh battery which is not lasting as long as my well used 4,600 mah ni-mh battery. I would have said that the 6,800 battery was not really this capacity if I didn't know better. the 4,600 mah was also depleting rapidly when new and not storing much charge in the first place.
It is the same with my 55 a/h agm battery. When new it was not lasting long at all but now I get a very good result from it after using it quite a few times.
I don't know if this is well known or not, but I have never seen anything on it. Does anyone know the reason for this and would I be able to understand the explanation if it is not a complicated chemical engineering problem. a battery is of course a chemical reaction delivering a electric current
Anybody else noticed this in batteries and knows the reason? is there any good literature on this giving for instance the number of times the battery has to cycled before it reaches its maximum storage capacity?
 

bountyhunter

Joined Sep 7, 2009
2,498
I have never heard of this problem with lead acid (AGM) batteries. Ni-Mh should not be doing it either. Lead acid typically show max capacity new and gradually decline with cycles. I am not sure why yours are doing this.

The only thing I can think of is perhaps the "new" cells sat on the shelf too long and grew some internal bridges that were current paths to degrade capacity and they burned away with cycling.
 

Thread Starter

petercl14

Joined Sep 29, 2012
3
that sounds like a distinct possibility" bounty hunter." I obtained the batteries through e-bay and got them cheaper than normal probably because they had been in the sellers possession for too long.
does that really happen i.e. internal bridges in the battery? anyway your explanation certainly would explain the facts.
does anyone else out there have any further ideas or agree with bounty hunter.
 

bountyhunter

Joined Sep 7, 2009
2,498
I know older Ni-Cads and NI-Mh grow internal bridges after the separators degrade over time.

I did get a new lead acid motorcycle battery once (shipped dry) that had an internal bridge of some kind. When I added the acid, it got very hot without any charging (I quickly set it way out in the back yard by the fence). It cooled down but would not take a charge. I let it set a week and then charged it up and down a few times and it then worked normally.
 

Lumenosity

Joined Mar 1, 2017
461
Because a link to this thread still pops up when you search on battery capacity...I wanted to add something for those who find it during later searches....like I did....

In response to post number 5.....

All lead acid batteries get very warm after you first activate them by adding acid. That's normal.
 

Lumenosity

Joined Mar 1, 2017
461
I've never really had a hydrometer test work for me. It seems to kinda sorta tell you the health, but not really the actual capacity

Maybe I just didn't use a good enough hydrometer.....
 

JoeJester

Joined Apr 26, 2005
4,077
I've never really had a hydrometer test work for me. It seems to kinda sorta tell you the health, but not really the actual capacity

Maybe I just didn't use a good enough hydrometer.....
Do you know the history of that battery? Are you the first owner?

Anyway, here's a tale of woe about two lead acid batteries. These batteries were connected in series to start a 24V a 300 kW emergency generator.

Symptoms: They would not turn over the motor. The no load voltage was 12V, the hydrometer read within the fully charged range.

I replaced the batteries because my EPO (leading mechanic) stated he had nothing but trouble with those batteries. The new batteries were over 100 dollars each. We renewed those batteries. We put the failed batteries under a test after charging them. The AH rating of the battery or CCA of the battery escapes me as it happened 20 years ago. Using enough high power resistors to create a load, we connected the battery and watched the voltage drop. We took a hydrometer reading and voltage reading hourly. The voltage decreased but the hydrometer remained in the "fully charged" range. After about four hours, the battery voltage dropped to about 8 volts but the hydrometer read "fully charged." So I asked the non-rated person working in the area to tell me about the maintenance they were doing on the battery. He explained they added "acid" as that is what he was told to do. I asked who told him and he answered me. I said ... he lied to you ... and then held a training session on batteries and battery maintenance. The hydrometer is suppose to decrease as the battery discharges.
 
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