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Thank you for your help :)

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Ok then, thank you for your reply. :)
 
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SherylinRM said:
Cell data.
8 lifepo cells
280 Ah
About 24 volts
I use them on my mobility scooter.
I use the Daly BMS when charging.
I use a ten amp charger when charging my cells.

Ok so I have been using my battery bank by charging to 3.345 volts and not going below 3.2 volts at most.
More often I charge to 3.32 to 3.35 volts and discharge to 3.25 volts.
Everything has been going well for about 18 months until today.

Today I was going up a steep hill when the motor over heated and popped the 50 amp circuit breaker.
No problem. I sat a couple of minutes and pushed it back in and started again. After a little bit it popped again.
I waited again and put it back in place.
By this time i was at the top of the hill and it did not pop again.

However, the machine was slower than usual. Also the dial showed that the voltage was a lot lower than it should have been.
As I continued on my way home the machine was still slower than usual and the voltage indicator went down to one lit led.

When I got home I checked the cells and they were all fine except for one which read 0.207 volts.
I thought that this had to be wrong so I used another tester but it said the same thing.

I have no clue why this would have happened. The cells are less than two years old and I have tried to baby them since I got them.

Any ideas what happened?

This is the first time the motor has over heated when using these cells. But as the circuit breaker is rated for 50 amos. And the cells are 280 Amps. I do not see how they could possibly have over heated the cells.

Ideas? Thank you :)

Quick Edit: How dangerous is this? Or is it now so dead that I have nothing to worry about or what?
Thank you. :)
Click to expand...
Hi there - I have a similar battery cell configuration to yours and wondered why you only charge to 3.345 volts? Reason being I try to charge mine to 3.65 volts but can never get all cells this high and most sit on exactly 3.345 Volts no matter what I do. So wondering if this is what they are supposed to be charged to?
 
I hope this helps. :)
 
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I’d focus on the low voltage as being a hard line to follow but push you high voltage (3.45/3.6) limit say every other charge, or every 5th charge to allow balancing to happen
 
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SherylinRM said:
Well if you look at some posts here. They suggest to charge only to 80% and that is 3.325. I go a bit above that to 3.345 which is above 80 but below 90%.
I also do not allow them to get below 3.2 volts which is about 20 %.

This along with compression [mildly] will allow them to supposedly last for 20,000 cycles. Or basically the rest of my life.

Anyhow, that is why I do it.
I hope this helps. :)
Click to expand...

Certainly does - thank you. Just reading some other posts which suggest setting the max V to 3.55 or 3.475. Looks like my BMS does this anyway though. SO maybe I don't have a problem at all although I've heard it stated many times that voltage doesn't really correspond to SOC and guess this would be particularly true around the middle voltage range.
 
So no problems here with SOC for me LOL.
 
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Interesting, thank you.
 
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Depp you have a cell or cells that reach the 3.65 while some cells are still at 3.3. Your bms stops the charging to protect the high cells. All of the cells average together equal 3.4. Ideally you need to top balance them. Alternative is to use a balancer and keep an eye on them.

OP could gently change the dead cell it could recover. REMOVE THE CELL AND CHARGE IT OUTSIDE AWAY FROM ANYTHING. A bench power supply would be the only way. Start at like 2 volts at 1 amp for a while ( hours). Stop charging and check cell voltage. If it responds continue to charge slowly increasing.
You must use a properly sized BMS all the time with these cells or get some AGM batteries.
The 280’s are at least twice as much capacity as you need based on the little cycling you describe. The BMS is capable of some cell balancing but it doesn’t start until around 3.5 volts per cell. Also these probably needed to be top balanced when you got them. I recommend you watch some of Wills videos on building LFP batteries.
 
SherylinRM said:
Thank you. And no, I have never had a cell go below 3 volts before. And my records show I have not even gotten close to that either.
Click to expand...
What records? The ones you don't have for when the battery is actually in service? Unless you've been riding the scooter with a VM on every cell, you have no way of knowing anything. Case in point, you have a cell sitting at 0V.
 
acdoctor said:
Depp you have a cell or cells that reach the 3.65 while some cells are still at 3.3. Your bms stops the charging to protect the high cells. All of the cells average together equal 3.4. Ideally you need to top balance them. Alternative is to use a balancer and keep an eye on them.

OP could gently change the dead cell it could recover. REMOVE THE CELL AND CHARGE IT OUTSIDE AWAY FROM ANYTHING. A bench power supply would be the only way. Start at like 2 volts at 1 amp for a while ( hours). Stop charging and check cell voltage. If it responds continue to charge slowly increasing.
You must use a properly sized BMS all the time with these cells or get some AGM batteries.
The 280’s are at least twice as much capacity as you need based on the little cycling you describe. The BMS is capable of some cell balancing but it doesn’t start until around 3.5 volts per cell. Also these probably needed to be top balanced when you got them. I recommend you watch some of Wills videos on building LFP batteries.
Click to expand...
Many Thanks Doctor, yes that;s correct - cell 1 reaches the maximum voltage I set within the BMS (3.65V) very quickly but all the others are around 3.3V except Cell 5 (3.4). The balance function in the BMS then does it's job (eventually) but as soon as it turns on the charger the same thing happens again. I think you're suggesting I manually charge each cell separately (carefully checking voltage) which I might try so I can top balance. Presently I'm working on another theory that the charger I have always outputs 10.5 amps (rated 12 amps). The DALY BMS I have is rated 50A for charging (lol) but I'm thinking the charging amps are too high? So have ordered a 4 amp charger to see if that charges in a more orderly fashion. Several people have reported this problem with the DALY BMS on this forum so I'm wondering if this is the cause.

Only issue is that when I disconnect the charger from the battery and put a load on the voltages seem to equalise very quickly (15mins - 1.5 A load )to about 3.4 volts. So maybe the voltages the BMS reports are not accurate anyway? Have also seen on the forum that innacurate voltages is also an issue with some DALY BMSs so have contacted DALY to see if there is a firmware upgrade for my BMS which others have found solves this particular problem.
 


Thank you for replying. :)
 
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Have a nice day now.
 
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SherylinRM said:
Not really sure what you are saying here.
Are you actually suggesting I try to recover this cell?
Click to expand...
I’d recommend avoiding any work/use of the cell and source a replacement.

My advice is for continued use of a pack without a BMS (which I strongly suggest you use, unless you enjoy buying cells).
 
Ok thanks
 
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When you get yourself organised, if you absolutely refuse to take your BMS with you, consider getting a small 4 cell voltage monitor that you could mount on your handlebars. That way you have at least some chance of avoiding a repeat of your current situation.
 
Thank you.
 
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Ok thanks guys for your helped that actually tried to help. :)
 
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Bye and have a nice day.
 
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J Depp said:
Hi there - I have a similar battery cell configuration to yours and wondered why you only charge to 3.345 volts? Reason being I try to charge mine to 3.65 volts but can never get all cells this high and most sit on exactly 3.345 Volts no matter what I do. So wondering if this is what they are supposed to be charged to?
Click to expand...
Best to start a new thread. Post some details. You will get lost in here.
 
A good sport would have left the original post for others to read and learn.
Nothing will make sense to others now.
 
SherylinRM said:
Have a nice day :)
Click to expand...
That's not how the forum should work. The edit button isn't here so you can delete all the information!

That could be useful information for others in the future.

@Will Prowse
I don't think I've ever called on you before, but does it bother you that the OP deleted edited their posts to remove all content?
 
Okay then.
 
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