Problems with Batteries Low Cell Voltage - happened to four different batteries.

[pulper11]

If thats' the original cell that was very low, it is going to take a very long time to charge, and the voltage will take forever to increase.

It's certainly taking longer to charge each cell (and that particular low cell took a longer time).

Is that going to be a recurring theme then with this battery? I was hoping that lower capacity just means that it would not achieve a certain voltage. And seeing that it does achieve high voltage with these cells (albeit slowly), I was hoping that the battery is ok and just needed to be top balanced. not trying to argue here...just making sure I understand. Again, this is an already replaced battery that I was hoping might be able to get back to a good working condition.

Thanks.

 

[sunshine_eggo]

It's certainly taking longer to charge each cell (and that particular low cell took a longer time).

Likely at a lower state of charge overall.

Is that going to be a recurring theme then with this battery?

Hopefully not. Hopefully, the battery was just built with cells at horribly mismatched states of charge.

The ~15 min top-off of all cells should look about the same as the other battery if the outlook is positive.

 

[pulper11]

Likely at a lower state of charge overall.



Hopefully not. Hopefully, the battery was just built with cells at horribly mismatched states of charge.

The ~15 min top-off of all cells should look about the same as the other battery if the outlook is positive.

Thanks! Definitely worth the effort to do this since it is already opened up and I'm setup with the DC power output.
Appreciate your help!

 

[pulper11]

I had an issue with the two most recent batteries that were received from trophy (#3 and #4).
These were very recently top balanced.
I've had about 3-4 days now with little sun. I have been using these batteries little during that time. Mainly LED lights and a fan at night.
Last night the fan went off during the night and the lights wouldn't turn on. I checked solar assistant and found the image posted below. I checked the batteries themselves and they had the red light and were LV.
My question is - Is it odd to have one pack at 95.6% SOC with 114.8AH out of 120AH, but have a voltage of 49.8? These numbers are very similar for the other battery as well if you scroll on the image.
I'm a little confused with this. Both packs also have one cell that is well below the other cells.
Again, these two packs were very recently top balanced.
I'd appreciate any insight.
Thank you!

 

[pulper11]

Can someone help me with accurately measuring (or at least estimating) the state of charge of a battery based on voltage?
These two batteries show a SOC of over 99% with voltages of 51.1V and an average cell voltages below 3.2 Volts.
Thank you.

 

[sunshine_eggo]

Given the 0a state,

You're at about 3.2V, so SoC is almost certainly below 20%.

 

[Sojourner1]

When you say top balanced what do you mean? How did you do it?

I had an issue with the two most recent batteries that were received from trophy (#3 and #4).
These were very recently top balanced.
I've had about 3-4 days now with little sun. I have been using these batteries little during that time. Mainly LED lights and a fan at night.
Last night the fan went off during the night and the lights wouldn't turn on. I checked solar assistant and found the image posted below. I checked the batteries themselves and they had the red light and were LV.
My question is - Is it odd to have one pack at 95.6% SOC with 114.8AH out of 120AH, but have a voltage of 49.8? These numbers are very similar for the other battery as well if you scroll on the image.
I'm a little confused with this. Both packs also have one cell that is well below the other cells.
Again, these two packs were very recently top balanced.
I'd appreciate any insight.
Thank you!

View attachment 181102

 

[pulper11]

Given the 0a state,

You're at about 3.2V, so SoC is almost certainly below 20%.

Thanks. Since the batteries themselves don't seem to be reporting SOC correctly, is there a way for me to measure it?

 

[pulper11]

When you say top balanced what do you mean? How did you do it?

Starting with this post should explain it:

Problems with Batteries Low Cell Voltage - happened to four different batteries.

What is your over voltage release setting? That's when it will reconnect to allow charging again. Also, your trying to turn the higher voltage in that one cell into heat. The BMS can probably only do this at 40mA or something tiny. If you can get inside the battery, you can do this manually at...

diysolarforum.com

Then read the following three or four posts through post 58.

I cycled through each cell a second time after doing it a first time, as suggested by @sunshine_eggo

 

[sunshine_eggo]

Thanks. Since the batteries themselves don't seem to be reporting SOC correctly, is there a way for me to measure it?

No. SoC is not measurable. It's calculated.

Start with a known condition, typically 100% based on cell voltage > 3.50, then measure current in and out compared to capacity.

Your only option is what we've done - estimate based on voltage. Less than 20%.

You need to charge them to full.