HELP PLEASE I think I may have some bad cells

[Moltensurf]

I got some battery cells on Alibaba I hooked the cells together, to top balance them but it was taking forever. 8 cells. I decided to break the pack in half into two separate 12 V batteries. I put one on a standard battery charger that works well. The other I left on a TuffIom battery charger 3.65amps. When I came back sometime later the 12 volt bank I hooked up to my smart battery charger said bad battery. The cells in the bad 12 volt block; I am individually charging the cells with the small charger.
I am charging the other 12 V bank with the smart charger.
The batteries are wired in parallel with bus bars. What I find strange is if I touch my DC meter to the positive and negative on that 12 V block it still reads 3.31 if they are joined together in parallel should they not be 12 V?
I am trying to test these babies, so if there is something wrong I can file a dispute. Any advice out there would sure be helpful
thank you

 

[Jim Burrow]

connecting them in parallel doesn't increase the voltage. In parallel, you will see the 3.31 volts if all batteries are good. you will get a lower reading if you have a bad battery or not fully charge to that of the other cells. To add voltage to your battery pack, they needed to be connected in series.

 

[Moltensurf]

connecting them in parallel doesn't increase the voltage. In parallel, you will see the 3.31 volts if all batteries are good. you will get a lower reading if you have a bad battery or not fully charge to that of the other cells. To add voltage to your battery pack, they needed to be connected in series.

Thanks for the reply I really appreciate it.

 

[Gazoo]

What I find strange is if I touch my DC meter to the positive and negative on that 12 V block it still reads 3.31 if they are joined together in parallel should they not be 12 V?

The fact that you don't know the difference between connecting cells in parallel and connecting in series, and are attempting to charge the cells connected in parallel with a 12 volt charger is a testament that you have no clue what you are doing.

My advice to you is to stop everything you are doing immediately and learn something before you damage your cells. You had plenty of time to read up since you joined the forum in October. Why didn't you?

You posted in another thread you own an Overkill Solar BMS. Did you bother to read the instructions? Everything is explained including parallel top balancing and how to connect the cells in series with the BMS after top balancing is completed. Sorry to be so crude. But you should have done your research before you ordered the cells so you would know how to properly do things. There are no excuses. LFE cells are not toys and not to be played with.

I hope you take the time to study the resources section of the forum, read the threads that pertain to you, read the Overkill instructions....and so on so you can be successful constructing your batteries.. BTW, Here is another good read from Nordkyn Design. Good luck.

 

[Moltensurf]

Yep, I screwed up. I have been wanting to get my solar system going for a long time, but I’ve been super busy with work. I had some money so I bought my batteries, while I still have money. I am not completely ignorant to solar, are used to live on a sailboat and had a system i installed. It’s been a little while and I don’t mess with solar batteries every day so I am kind of rusty, there is a lot of information to learn and retain. I finally tested at one of my cells. The manufacturer said it was a 400 amp hour 24 V bank. I am just trying to sort things out if I have a problem. It looks like there is not as much capacity in the sales as the manufacturer claims

 

[Moltensurf]

The fact that you don't know the difference between connecting cells in parallel and connecting in series, and are attempting to charge the cells connected in parallel with a 12 volt charger is a testament that you have no clue what you are doing.

My advice to you is to stop everything you are doing immediately and learn something before you damage your cells. You had plenty of time to read up since you joined the forum in October. Why didn't you?

You posted in another thread you own an Overkill Solar BMS. Did you bother to read the instructions? Everything is explained including parallel top balancing and how to connect the cells in series with the BMS after top balancing is completed. Sorry to be so crude. But you should have done your research before you ordered the cells so you would know how to properly do things. There are no excuses. LFE cells are not toys and not to be played with.

I hope you take the time to study the resources section of the forum, read the threads that pertain to you, read the Overkill instructions....and so on so you can be successful constructing your batteries.. BTW, Here is another good read from Nordkyn Design. Good luck.

Feeling super stressed out, because I dropped a lot of money on these battery cells

 

[snoobler]

Rightfully so.

Stop everything you're doing. Don't touch a cell or a charger. Go here:

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

Click the orange download button, save the PDF, open it and read it. If you don't understand something, ask questions.

 

[Moltensurf]

Rightfully so.

Stop everything you're doing. Don't touch a cell or a charger. Go here:

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

Click the orange download button, save the PDF, open it and read it. If you don't understand something, ask questions.

Thank you

 

[Moltensurf]

Thank you

I watch this video, and top balanced my cells. I was going to do a capacity test on the whole bank, but the tester only excepts 12 V. Thinking about getting a 24 to 12 volt converter to run the test on the whole bank. I tested at one of the cells, with this little heater unit. I am in the process of testing another one.
Are each of these cells I bought supposed to be 200 amp hours, or am I mistaken?

 

[John Frum]

I watch this video, and top balanced my cells.

Did you read the doco that @snoobler linked?

 

[Moltensurf]

Did you read the doco that @snoobler linked?

I did read that, and I’m studying other stuff right now

 

[John Frum]

New cells are usually shipped at ~50% state of charge.
The voltage upon reciept should be ~3.29 volts.
16 200 amp cells in parallel will require ~1600 amp hours to completely charge.
A typical bench power supply can offer ~10 amps.
At 10 amps it will take ~160 hours.
The doco that @snoobler linked will show you a way to get the job done much quicker.

"~" = approximate

 

[Moltensurf]

Did you read the doco that @snoobler linked?

I am looking at it right now. I was a little confused I watched Will’s video. Will said if the cells are not already topped up, to make 2 4S batteries and charge them with a traditional charger; then top balance them. He did not mention in the video to use the BMS. I do not have a 12 V BMS, I only have a 24 V bms.
in the link snoobler sent me in step 3 pre charging it says to put the bank in parallel and use bench power supply to bring the cells up.

 

[John Frum]

I am looking at it right now. I was a little confused I watched Will’s video. Will said if the cells are not already topped up, to make 2 4S batteries and charge them with a traditional charger; then top balance them. He did not mention in the video to use the BMS. I do not have a 12 V BMS, I only have a 24 V bms.
in the link snoobler sent me in step 3 pre charging it says to put the bank in parallel and use bench power supply to bring the cells up.

If you have an 8s bms make an 8s battery then charge to high cell cutoff.
Repeat for the process for the other 8 cells.
You may have to bleed some energy off the high cells before you put them in parallel to finish them off.
Are the cells connected in parralel or serial now?
What voltage are the cells at?

 

[Moltensurf]

If you have an 8s bms make an 8s battery then charge to high cell cutoff.
Repeat for the process for the other 8 cells.
You may have to bleed some energy off the high cells before you put them in parallel to finish them off.
Are the cells connected in parralel or serial now?
What voltage are the cells at?

Right now I have the batteries connected in parallel. I had eight batteries connected. First I did what it said in Will’s video I made 2 4S cells and charge them with my battery charger. Then I connected them in parallel, with my bench charger set to 3.65. The voltage never got down to zero it was bouncing around between 80 and 30 and back to 80. I took two of those batteries out. I tested the capacity on one cell; I am in the process of testing the capacity on the other cell.

 

[John Frum]

The voltage never got down to zero it was bouncing around between 80 and 30 and back to 80.

The voltage of an 8s lifepo4 pack should never exceed 29.2 volts.
I think you might be talking about amperage.
But the question I was asking is what voltage are the cells currently at?
Since they are in parralel it should not exceed 3.65 volts and is most likely ~3.3 volts.

 

[Moltensurf]

If you have an 8s bms make an 8s battery then charge to high cell cutoff.
Repeat for the process for the other 8 cells.
You may have to bleed some energy off the high cells before you put them in parallel to finish them off.
Are the cells connected in parralel or serial now?
What voltage are the cells at?

The pack of cells is at 3.32 V at the moment it is not connected to anything just resting in parallel

 

[Moltensurf]

The voltage of an 8s lifepo4 pack should never exceed 29.2 volts.
I think you might be talking about amperage.
But the question I was asking is what voltage are the cells currently at?
Since they are in parralel it should not exceed 3.65 volts and is most likely ~3.3 volts.

Sorry I was speaking about the Sorry I was speaking about the Voltage on my bench power supply. It is supposed to drop to zero when everything is balanced.

 

[John Frum]

Sorry I was speaking about the Sorry I was speaking about the Voltage on my bench power supply. It is supposed to drop to zero when everything is balanced.

I think you are mistaken.
The current(amperage) should approach zero as the charge voltager and battery voltage converge typically at 3.65 volts.

 

[Moltensurf]

The voltage of an 8s lifepo4 pack should never exceed 29.2 volts.
I think you might be talking about amperage.
But the question I was asking is what voltage are the cells currently at?
Since they are in parralel it should not exceed 3.65 volts and is most likely ~3.3 volts.

Yes they are at 3.3 V