Ampere Time 24V LiFePO4 battery discharges during the night, with no load--fixable?

[rsi77]

Hi All,
Last winter my solar system stopped working, system simply stopped--no lights, no noise on inverter. I had too many other projects, plus work travel, etc. so I didn't try to troubleshoot then. But yesterday I finally had a look the system:
2 x 24V Ampere Time 100Ah in series for a 48 volt system

• 1 battery measures 24V
• 2nd battery measures 8 volts

I charged the low battery using a panel, and connected it back to the system. The Growatt sprang to life and started charging the batteries 53V.
I currently have no load on the system.
In the morning the system was not running at all. I measured the voltages on the batteries--same as before:

• 1 battery measures 24V
• 2nd battery measures 8 volts

Is there hope for the 2nd battery? Or does it simply need to be replaced?
Last fall I had a similar issue, but after recharging with the solar panel, everything seemed to be working.
I know there are ways to correct bad cells if you have access to the individual cells, but is there anything that can be done with the Ampere Time battery, which is sealed?

Last winter is was < 32F outside, but I don't think my garage (where the system is stored) got below freezing,(but I'm not positive about that).

System = Growatt SPF 3000TL LVM-ES (not connected to line power, only to solar array and batteries)
2 x Ampere Time 24V 100 Ah
6-panel array give 198 input voltage (no load)

Thanks!
Ron

 

[42OhmsPA]

Charge each battery, separately, to 100% then put them back in series.
What do you mean you charged it back up with a panel?

The idle consumption is likely draining the batteries down overnight and the packs are way out of balance.

 

[rsi77]

To charge separately, do I need a 24v battery charger, or will a solar panel do?
"I charged it back up with a panel" means I connected it to a solar panel until it read 24 volts (on par with the other battery), but I realize now the voltage reading itself is not a good indication of equivalent charge.
Should I balance out the batteries by connecting them to each other for a time, prior to placing them in series again?
Thanks,
Ron

 

[cs1234]

To charge separately, do I need a 24v battery charger, or will a solar panel do?

You need a 24v lifepo4 battery charger. A solar panel won't do unless it's connected to a 24v capable solar charge controller.

Should I balance out the batteries by connecting them to each other for a time, prior to placing them in series again?

No, you need to charge each battery separately with the above mentioned charger, then you can put them back into series.

Don't connect the batteries in parallel together with more than a 1vdc difference between them. You are blasting that poor 8v battery with huge current from the 24v battery every time you parallel them up.

 

[Rednecktek]

The idle consumption is likely draining the batteries down overnight and the packs are way out of balance.

The standby draw on those units is only about 60w so it shouldn't be near enough to drain the battery that low.

Yes, the batteries are out of balance, you need to get that 8v fully charged and see if it holds charge just sitting there not connected to anything.

You can probably do it with a panel and simple controller, but it'll take days.

 

[rsi77]

You need a 24v lifepo4 battery charger. A solar panel won't do unless it's connected to a 24v capable solar charge controller.

No, you need to charge each battery separately with the above mentioned charger, then you can put them back into series.

Don't connect the batteries in parallel together with more than a 1vdc difference between them. You are blasting that poor 8v battery with huge current from the 24v battery every time you parallel them up.

Clear enough. Thanks!

 

[rsi77]

The standby draw on those units is only about 60w so it shouldn't be near enough to drain the battery that low.

Yes, the batteries are out of balance, you need to get that 8v fully charged and see if it holds charge just sitting there not connected to anything.

You can probably do it with a panel and simple controller, but it'll take days.

Thanks.
I got it up to 25V with the panel. I'll leave unconnected over night and see how it reads in the morning.

 

[Rednecktek]

Just don't panic when it hits 26 and stays there forever. That's the flat and it takes a LOT of energy to get past that. If you think it's "close enough" let it charge for another day. Patience is a thing.

 

[rsi77]

Minimal loss of voltage with batteries disconnected. I will receive the charger on Wednesday--I will use that to bring both batteries to full charge. I like the idea of a green light to let me know when it's fully charged.