12v, 200Ah, tublar tall lead acid batteries

[Houston Raven]

Sirs,
Originally I had a 24V UPS that lights up my home with 2x200 Ah tublar flooded batteries hooked up in series (24v). Those batteries are about 8 months old. Now I installed a 6x545w PV solar system with 60A MUST controller/charger plus 2 more 200Ah batteries in series with the old ones to give me (48v). I've noticed that the new ones charge at 14.5-15v & the old ones charge to 12.4-12.8v only? All batteries in series (48v) charging at 10A from the controller & the inverter when power from electric company available.
Is there a way to make all batteries equalize at same voltages knowing that my inverter has an equalization button in which I did perform equalization for 30 minutes only, but still they read: -
Old batteries 12.4 & 12v
New batteries: 14.2 & 15v
Please can anyone help & direct to how can I make all 4 batteries voltages equal & how?

 

[OzSolar]

Hello Houston Raven,

This a common problem with mixing older and newer batteries. You've got to make sure they are all at the same state charge before you put the system in service.

I suspect your old and new batteries are at radically different states of charge. Since your batteries are flooded you can use a hydrometer or refractometer (my favorite) to determine the state of charge of your batteries. These are the kind of batteries that you can open up cap on and see the electrolyte, right?

Your were on the right track by using the equalize function on your charge controller except 30 minutes is not nearly long enough, especially when your batteries are that far out of whack.

If was me I'd take the system out of service until you get this resolved. Those older batteries are danger of being ruined because they are such a low state of charge.

There's a few options to choose from but lets start with the way I would do it.

Reconfigure your system back to 24v using the two batteries of the lowest voltage. Charge them batteries back ~15v each. Hold them there until each cell is at least 1.270 specific gravity. This will likely take more than one day.

Repeat that process with the newer batteries and don't put the system back in service until each cell in each battery between 1.265 to 1.275.

If you have any questions please also supply the exact model of your battery and a link to the manufacturer's care and maintenance documents.

 

[Houston Raven]

Hello Houston Raven,

This a common problem with mixing older and newer batteries. You've got to make sure they are all at the same state charge before you put the system in service.

I suspect your old and new batteries are at radically different states of charge. Since your batteries are flooded you can use a hydrometer or refractometer (my favorite) to determine the state of charge of your batteries. These are the kind of batteries that you can open up cap on and see the electrolyte, right?

Your were on the right track by using the equalize function on your charge controller except 30 minutes is not nearly long enough, especially when your batteries are that far out of whack.

If was me I'd take the system out of service until you get this resolved. Those older batteries are danger of being ruined because they are such a low state of charge.

There's a few options to choose from but lets start with the way I would do it.

Reconfigure your system back to 24v using the two batteries of the lowest voltage. Charge them batteries back ~15v each. Hold them there until each cell is at least 1.270 specific gravity. This will likely take more than one day.

Repeat that process with the newer batteries and don't put the system back in service until each cell in each battery between 1.265 to 1.275.

If you have any questions please also supply the exact model of your battery and a link to the manufacturer's care and maintenance documents.

Thanks a bunch for replying so soon. I will do exactly what you suggested, were planning to do it anyhow but was not sure it will work?
I will shut down the whole system, hookup the 2 old batteries in series & charge them as you mentioned up to 15 v, then do the same for the new ones. Will let you know very soon since I'm in lebanon & power only comes for 2 hours in 24. But I will run my gen set for that purpose.

 

[OzSolar]

Thanks a bunch for replying so soon. I will do exactly what you suggested, were planning to do it anyhow but was not sure it will work?
I will shut down the whole system, hookup the 2 old batteries in series & charge them as you mentioned up to 15 v, then do the same for the new ones. Will let you know very soon since I'm in lebanon & power only comes for 2 hours in 24. But I will run my gen set for that purpose.

Wow.. Lebanon and your power is off 22 hours a day. I suspect my utility isn't down 22 hours a year so I'm glad to try to help.

Please confirm that these are flooded batteries. My advice only applies to batteries with cells that you can add distilled water to yourself.

You might even have to take the system voltage up to 32 and hold it there. At 30 volts the highest SOC (state of charge) battery might be at 15.8 while the other one sits there at 14.2. You're really going to want to be checking the cells with a Hydrometer and making notes every few hours if at all possible.

Do you have access to a "stout" automotive 12v battery charger that plugs into your mains power? That type of charger probably won't take your battery to 15 volts but it can get it to 80% or better SOC. One rated to at least 20 amps would be ideal while one rated less than 10 amps probably will only put out 5 to 7 amps and will never make a dent in what you're up against.

 

[Houston Raven]

Yes Mr. Oz, howdy do?
I do have a 30 Amp. Charger where I started today with the process, it seems to be promising, as of now after couple hours I managed to bring up the battery from 12.4 v to 14.89v still in process till I reach the 15v.
I'm an American from Houston Texas living & married from a Lebanese woman. Corruption is everywhere, our ministers are ruthless & been having problems with power Generation for years, hope we get better soon, living only on UPS & PV, or diesel Generator?
Will keep informing you about the process periodically. Thanks a bunch.

 

[OzSolar]

Sounds like you've got it on the run now HR. There's the connection between your user name and Lebanon. It's very interesting to you hear your story. It's my pleasure to help.

UPS? Are you saying you've got a repurposed UPS vs. a standard inverter charger.

Voltage by itself is poor indicator of SOC (state of charge) so be careful using itself.

Volts and Amps together are better. Roughly speaking.... If it takes all 30 amps of your charger to hold the battery at 15 amps you've got a while to go. Versus you can hold the battery at 15v with 2 amps means it's either fully charged OR heavily sulfated.

Specific Gravity is the best. You need to get all of those cells up to ~1.270.