Cons of my battery bank? 8s4p

[Bitbin]

I have a 24v battery bank consisting of 32 used 80ah cells which in reality after capacity testing them gave be between 72 and 79 amps each. They are bloated and prob grade c but i didnt pay for them so cant complain.

I connected 4 of them in parallel for a total of around 290-300 amps and then 8 of them in series for 24v. Are there any cons of this setup? each 4 cells are counted as one cell in the bms now. Its been working great but i havent capacity tested it as a battery bank. Any advice is appreciated

Thanks

 

[Bob B]

I have a 24v battery bank consisting of 32 used 80ah cells which in reality after capacity testing them gave be between 72 and 79 amps each. They are bloated and prob grade c but i didnt pay for them so cant complain.

I connected 4 of them in series for a total of around 290-300 amps and then 8 of them in series for 24v. Are there any cons of this setup? each 4 cells are counted as one cell in the bms now. Its been working great but i havent capacity tested it as a battery bank. Any advice is appreciated

Thanks

I think you mean to say you have 4 of them in parallel and then 8 of those in series.

I have a pack with 2 cells in parallel then 4 in series to form a 12V battery, but none of those cells are bloated .... I would suggest that it is undesirable to have bloated cells in parallel that way and I wouldn't want that battery in my residence.

 

[Bitbin]

I think you mean to say you have 4 of them in parallel and then 8 of those in series.

I have a pack with 2 cells in parallel then 4 in series to form a 12V battery, but none of those cells are bloated .... I would suggest that it is undesirable to have bloated cells in parallel that way and I wouldn't want that battery in my residence.

Yea i mean parallel. Why would it be undesirable for bloated cells? I havent compressed them and they have enough air going through them

 

[Bob B]

Yea i mean parallel. Why would it be undesirable for bloated cells? I havent compressed them and they have enough air going through them

First of all, bloated cells in ANY configuration can be dangerous ..... with 4 of them in parallel, you are unable to monitor individual cells that may start to have problems ..... this makes the bloated cells even more dangerous.

Maybe you can post a picture of your pack so we can get a better idea how bloated they are.

 

[ScrotpusGobbleBottom]

I wanna see the spicy pillows!

 

[Bitbin]

First of all, bloated cells in ANY configuration can be dangerous ..... with 4 of them in parallel, you are unable to monitor individual cells that may start to have problems ..... this makes the bloated cells even more dangerous.

Maybe you can post a picture of your pack so we can get a better idea how bloated they are.

But wont the 4 cells always stay at the same voltage? So at 3.6 per cell maximum that doesnt seem too dangerous or im a wrong.

 

[wpns]

But wont the 4 cells always stay at the same voltage? So at 3.6 per cell maximum that doesnt seem too dangerous or im a wrong.

When one of the parallel cells shorts out, the other three will dump all their current into it.

 

[740GLE]

Agreed whats your definition of bloated? Share the pics!!! Have you taken them to above 3.5v?

 

[Bitbin]

Agreed whats your definition of bloated? Share the pics!!! Have you taken them to above 3.5v?

They are contained in a wooden box and ive covered them cant really take them out with ease. What i mean with bloated is they they arent straight when putting on a table laying down. They wobble a bit. It can be clearly seen that they are grade c at least. But they arent pregnant. Just not straight

 

[Bitbin]

Agreed whats your definition of bloated? Share the pics!!! Have you taken them to above 3.5v?

I charge them to 3.55-3.6.
28.4v as a pack

Cuz of around 5-10% diffrence in capacity the first cell that reaches 3.65 cuts the charging of and then the active balancer balances them to around 3.55 per cell by the end of the day.

 

[740GLE]

doesn’t sound that bad, when cells go bad they completely deform.

If you laid them flat on a table you think they’d have less than 1/4” of gap? Or more?

 

[Bitbin]

doesn’t sound that bad, when cells go bad they completely deform.

If you laid them flat on a table you think they’d have less than 1/4” of gap? Or more?

To be honenest havent measured how much but you could say half of them have some form of bulge on one side or both. But they arent compressed. Just taped together

 

[Bitbin]

Im very happy with it as i got 7kw of power each night that gets me through the whole night with the ac and fridge and the router and lamps working. Still got around 20-30% left when the sun comes up. I used to have 2 really bad lead acid batteries that would barely work until sunset.

Even though these are the "worst" kinds of lifepo4 cells as they are in best case grade c and have degraded 5-10% from the original 80ah rating. They are still 1000 times better than lead acid it feels like.

How nice would a 8s2p 560ah 24v lf280k setup be.