Battery Help

[Skispcs]

These two batteries have been on an Inverter/Charger since new. About 18 months.
Last weekend I noticed that I was able to smell these batteries. When I investigated, they were VERY warm.
I shut it down and let them cool, water levels are good. I did add a little distilled water as some were a bit low. I attribute that to them getting hot.
I took them outside and I have tested them with my load tester. They perform great on the load tester. In this image I have the load on and the coils are just starting to glow red.
I have tried charging them with 4 different chargers and they will "not take a full charge". I put that in quotes because I am not sure if it is the correct term. Reading the charger manual, they charge with a constant current until the battery gets to 14. something and change to float or some other mode.
These batteries have not gotten above 13.8 each so they stay in the first charge mode and get very hot and start off-gassing.

Because I have tried four different chargers with the same results, I guess something is wrong with both batteries. Am I missing anything? Anything I can do to try to rejuvenate these before I have to drop money on new ones?

[Carl]

Questions??


While at rest (not charging or discharging) what is battery voltage of each battery?

While tied to a charger and charging...What voltage is measured on each battery?

What current do you charge batteries ?  As they appear to be GROUP 29 or about 50 to 75 Amp Hour...SIX amps would be suggested charge rate ,if mine.

Have you used the inverter to discharge the batteries occasionally and recharge to help prevent sulfation??

Check each cell for specific gravity?  May be bad cell.

Battery life begins at manufacture date and while 18 months is a tad early,,,,they could be near end of life due to misuse.

[Skispcs]

At rest voltage is 12.75 on each battery, after a 5 second hit on the load tester.

When charging it has been different, but the latest was around 13.9 or 14.0 on each.

I have tried them on different chargers. The yellow marine charger is usually about 10A per battery, the NOCO only does 2.2 total so about 1A each.
The Inverter can charge at up to 30 amps when the batteries are in series for 24V.

I have not intentionally discharged this set of batteries. Have lost power a few times and they ran the equipment for a few hours each time.

I was looking for my specific gravity tester but have not found it yet. Since both batteries are doing the same thing, I am kind of discounting a bad cell in one but it is possible.
Normally this set of batteries is hooked up in series for a 24V Inverter. I separated them and was charging them separately in the hopes I could essentially equalize them.

Could be, I guess I put faith in an $800 Inverter/Charger, that it would maintain the batteries for me.
I hooked the inverter back up and am discharging the batteries with a 1.5KW load on the Inverter. I will let that run for a while and then hook back up to the charger and see what happens.

The one charger has a "desulfation" mode where it charges at 15 Volts. if all else fails, I will try that.

[Carl]

  The load tester indicates the batteries are still "OK" and you smelled the gassing due to charging at too high a rate for indoors...they will 'normally vent sulfur-dioxide  (rotter egg smell) gas when charged or discharged at a high rate. Lead acid batteries should not get HOT unless being charged at too high a rate in my opinion.It is normal to need to add a bit of water for the plates from time to time but indicates to me that you are charging them at a higher rate than is optimum. I wouldn't charge above 6 to 10 amps for one or both batteries (in series for 24 volts)  without expecting some boil off of fluid. This should be done in a ventilated area and while not the way I do it ,is not always harmful to boil or mix the chemistry a bit.

  I suggested a lower rate of charge some time back for a project that sounds like this and I think WHY I made the suggestion is beginning to show. Lead acid batteries have design limits as to charge and discharge and should be maintained,but not charged 24 x 7...sometimes the automatic chargers get it wrong...or JUST MAYBE,if the charger you had connected was capable of and had initiated a DESULFATION MODE  that can reach 15 volts or more and cause some heat,gassing,general mayhem.


  I suggest a monthly running of the inverter to test and EXERCISE the equipment that you expect to depend on and let it operate for at least a couple of hours noting the time and voltage at end of test while inverter is still under load ...so as to determine when batteries are weakening and should be replaced...About 3 to 5 years for what little I know about your system. The fact that they were warm...and smelled ....is not a bad thing,unless it is a trend.

Best I can do for suggestions now as my mind is loaded with chemo and morphine and a bit scrambled.

  IF hot batteries and smell becomes common...you should watch how much current that you charge with...I would not think it indicates bad battery.
PLEASE work a schedule to test run the equipment and mark voltage when in use for a period of time to best determine battery/system health.

[Skispcs]

Carl,

As a followup, I hooked both batteries backup in 24V series and reconnected to the inverter.
Hooked up a 1.5KW drain and let it run until the batteries were about 12.4 volts each.
THen plugged the inverter back in and it has been charging for about 24 hours.

The current through the battery cable has been about 4A according to the clamp-on ammeter and the batteries are at about 13.2V each.

If I read the manual correctly, it should stay like this until the batteries reach something like 14.4V and then change to absorption or whatever the next stage is.

I am trying to not get my hopes up as the batteries have been at 13.2 for 3 or 4 hours now without any increase.

[Carl]

  The readings appear about right for that current and the charge voltage....I usually get the voltage to 14.2 to 14.4 on each 12 volt battery while charging BUT ,once fully charged...the voltage per battery should drop to 13.2 to 13.5 as a maintenance charge level. Sounds like all is OK and you just somehow got in a continuous charge condition that caused the gas and hot batteries.