Equalization Question

[MBJ]

Hi there,

I've been running an off grid setup for 3 years with a 48v battery bank comprising of (16) Exide 6v deep cycle batteries @186AH (so 372 AH for the bank). Also, midnight classic 150, Spartan inverter/charger, and genset. 1.8kw solar. Admittedly, I have done a poor job equalizing over the past 3 years because the hydrometer that I had was crap and could not get enough fluid in it for a proper reading. So, today I finally got my hands dirty and took a full reading of all 16.

This was at 73% SOC on the whizbang junior.

Almost all cells read 1.26-1.27, with the exception of 4 cells. 2 cells had no reading and 2 cells had a reading of 1.215. Each "bad cell" came from a separate battery.

So the question is....Do I do a big EQ charge on the whole bank? or do I take each "bad" battery out of the system and try to equalize it on its own?? OR do I need to replace all my batteries....hoping it isn't the latter, but I figure its best to expect the worst.

Thanks,

Matt

[chrisski]

I’ve only equalized once.

I would do it with t the whole bank. Tearing down and rewiring batteries for me is not an easy thing and would require making more cables.

Can you elaborate on the no reading cells? Was the hydrometer off the scale or not floating?

I’m assuming the readings you gave were for a fully charged battery. The specific gravity comes out to about 73% just like you said.

[MBJ]

I will try equalizing the whole bank tomorrow. I have a "spinning wheel" type of hydrometer (midnight solar hydrovolt), so when I filled the bad cells with electrolyte, the wheel just didn't seem to spin at all.

[chrisski]

I got a glass Deka Hydrometer from an auto parts store. Not the cheaper plastic version. THe glass one worked fine to me.

[MBJ]

So, I've equalized twice, once for 2 hours and now today for 4 hours. I'm seeing some improvement in the SG of the bad cells.

Question: why does the battery bank voltage go down on the charge controller the longer I equalize? I have my eq set to 63 volts. It will hit 63 volts for the first hour, then fall to 60 volts by the third hour. Roughly 40 amps charging between the solar and the genset.

[SunEagle]

So, I've equalized twice, once for 2 hours and now today for 4 hours. I'm seeing some improvement in the SG of the bad cells.

Question: why does the battery bank voltage go down on the charge controller the longer I equalize? I have my eq set to 63 volts. It will hit 63 volts for the first hour, then fall to 60 volts by the third hour. Roughly 40 amps charging between the solar and the genset.

It sounds like that battery bank will never be good again. Most batteries that are near the end of their life will charge up and quickly lose voltage because the plates are bad. IMO no amount of equalizing will help get your battery system working the way you want it.