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lifepo04 280ah eve cells capacity testing are these bad cells?

Jorvs

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Feb 21, 2021
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bought new cells eve 280 cells fully charged them and then bottom balance them connected them in parallel to bottom balance
the amp = 19 -21 mostly and U use a hair dryer as my load

I just notice that one cell no 3 is already 3.6 while others are not seem there voltages way off is here the image
sorry dint save a screen shot when it was full charge but as you can see here that cell 3 voltage is really high this image is when I just got started to capacity test
fully charged.jpg

after 6 hours this happened the test was finished the cell 1 hit 2.5v and the test was done
pic2.jpg

can some tell me if I did something wrong..
I tested my old 100ah cells and it hit 94ah pretty close to its capacity this ones way off

the 2 other cells seem fine? can some had this experience may be I did something wrong? and my cells were actually good
 
You said you fully charged the cells. Did you top balance them before hooking them up as a battery?
the inverter stop charging the cells sorry I dint take a screen shot forgot too

but the BMS says its not taking any more amp so it must be.. or a cell hit 3.6v too fast
and the BMS was also set if a cell hits 3.6 it will stop charging the volts of the cells were close to first image.
that image when I just started to start the capacity test...



after a full charged
I connected in parallel when a few hours tested voltage its was pretty close..
and I charged it again in 12v series connection for 20 minutes and begin the test
 
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Can you post a pic of your BMS settings? The BMS should NEVER let any cells get below 2.5V. Most folks set the low disconnect to ~2.8V or something above where the wheels come off.
 
the inverter stop charging the cells sorry I dint take a screen shot forgot too

but the BMS says its not taking any more amp so it must be.. or a cell hit 3.6v too fast
and the BMS was also set if a cell hits 3.6 it will stop charging the volts of the cells were close to first image.
that image when I just started to start the capacity test...


Why did you bottom balance them instead of top balance them?
sorry if I used a wrong term

what I did is top balance correct if I did my top balancing wrong or its called bottom balancing
I got 4 eve cells connected them in parallel but when I tried to used my old power supply to give them a 3.6v charge but it was broke
I ordered a new one but will take weeks...


so what I did is connected them is series to 12v and fully charged them. (1 cell hit 3.6 to I assumed that was fully charged)
after that I connected them in parallel again to balance it self
i know the time was kind of short for just a few hours I was testing them out fast as I can.. the warranty here in my area is very hard when days comes by they wont replace your battery bad battery..

may I ask as you can see at the image of the bms?
can balancing effect it that much?
there way too off?
the test was only 6 hours and 20amps?
 
Can you post a pic of your BMS settings? The BMS should NEVER let any cells get below 2.5V. Most folks set the low disconnect to ~2.8V or something above where the wheels come off.
yes the default was 2.8v
sorry I set mine to 6.5v to 2.5v just for capacity testing..


that I see in YouTube. to get a really fully capacity of your new batteries
this his channel
DIY Solar Power with Will Prowse
he dint actually says what settings on 1 video

I just piece by piece what he is saying in some videos and come ups
that it would be fully charged at 6.5v and fully discharged at 2.5v


feel free to correct me.. If I got it wrong
 
OK so you haven't completed a top balance due to a broken power supply.

I think the only real fix is properly top balancing. You weren't able to, and the cells weren't close enough in SoC, so your cells are all over the place. You could charge them in series til the BMS does a HVD, then use some sort of load on the high cell to bring it down some, then charge again until you hit a high cell, and repeat bleeding off a little bit until the other cells "catch up." Might end up having to bleed 2 or 3 cells to get the last one up there.
 
if some are asking they why did I balance it out that way..
putting in series of 12v and then charging them in an inverter.. and connecting them in parallel in a few hours only..
tested with a tester the last 3 digit of the volts different for each cell they look balance enough for me

so I connected them again in series charged them about 20 minutes and then do a capacity test..


the warranty is kind of hard in my area. i am on island separated from the capital city where the I ordered it
this was the fastest way I know to balance it out.. if I was to go there and complain I will ha to take a plane or a ship to get there..


I ordered my equipment separately in an app similar to shoppe(warranty here are hard when days comes to pass)
battery came first and the inverter second my new bms was not even here yet..
I am using my old bms on my 100ah battery I am just changing the capacity to 100ah on the settings when I switch them up..
 
OK so you haven't completed a top balance due to a broken power supply.

I think the only real fix is properly top balancing. You weren't able to, and the cells weren't close enough in SoC, so your cells are all over the place. You could charge them in series til the BMS does a HVD, then use some sort of load on the high cell to bring it down some, then charge again until you hit a high cell, and repeat bleeding off a little bit until the other cells "catch up." Might end up having to bleed 2 or 3 cells to get the last one up there.

may I ask was the few hours was not enough?
the last 3 digit in of the volts were different when I started it...

was that not balancing enough to hit this hard to be this way off when you load testing final result seemed there too way off if the problem was just balancing..

feel free to correct me
 
putting in series of 12v and then charging them in an inverter.. and connecting them in parallel in a few hours only..
Putting them in parallel and seeing if they equalize is a good thought but it does not work that way (it would have helped most of us at one time or another if it did!)
 
Charge up your battery again with the BMS connected . When the cell voltages start to diverge, connect a load across the high cell for several seconds whilst watching the display of cell voltages. A suitable load is a car headlamp bulb. After a little experience you will be able to judge how long to apply the load.
If things start happening too fast reduce the charge volts or disconnect for a short time. The objective is to have all the cells within about 0.050 differential above 3.50 cell voltage.

Mike
PS, sorry Sparky, was typing as you posted .
 
Label your cells and take notes on the one that charges highest and discharges lowest. Having good notes goes a long way when diagnosing issues.
 
OK so you haven't completed a top balance due to a broken power supply.

I think the only real fix is properly top balancing. You weren't able to, and the cells weren't close enough in SoC, so your cells are all over the place. You could charge them in series til the BMS does a HVD, then use some sort of load on the high cell to bring it down some, then charge again until you hit a high cell, and repeat bleeding off a little bit until the other cells "catch up." Might end up having to bleed 2 or 3 cells to get the last one up there.
thanks I will try that.. thanks for your suggestion...
greatly appreciated..
 
Label your cells and take notes on the one that charges highest and discharges lowest. Having good notes goes a long way when diagnosing issues.
I will.. thanks for that suggestion
greatly appreciated...
 
Charge up your battery again with the BMS connected . When the cell voltages start to diverge, connect a load across the high cell for several seconds whilst watching the display of cell voltages. A suitable load is a car headlamp bulb. After a little experience you will be able to judge how long to apply the load.
If things start happening too fast reduce the charge volts or disconnect for a short time. The objective is to have all the cells within about 0.050 differential above 3.50 cell voltage.

Mike
PS, sorry Sparky, was typing as you posted .
can I connect the bulb on a cell while the cells are connected in series on a bms? is that safe? it wont short or some thing?
 
You are 'shorting' current through the bulb to take power out of the cell and lower its voltage. The bulb limits the amount of current.
You need to take care that your 'test probes' on the wires to the bulb are suitable, this could be as simple as a few mm of the cable wire core that you 'prod' on the cell terminations or the buss bars to the cell.
As you lower the charge on the cell one of the others may become the 'high cell' so you switch your attention to that.
It's a bit like 'wack the mole', keep moving the load to the high cell for a few seconds when that cell becomes the cell with the highest voltage.
When working with cells take the usual safety precautions using eye protection, no metal jewelry or rings, insulated tools.

Mike
 
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