significant voltage difference before and after BMS

[Pattap]

Hi all. My setup is a 4s lifepo4 280ah with heyo BMS. I had to replace one cell after two years of no issues whatsoever. I have put a new cell in back to the pack in order to charge them to 3.6v so I can top balance. Since I have only a small charger, 6a I thought I'll connect it to my solar that's controlled by epever 40a controller. The controller however refuses to charge due to the voltage reading that's 14.1 whereas when I measure before BMS it gives me 13.3v. Now I have no idea if it's the bms that has gone faulty or I'm missing something stupid here. Like I said this worked for two years with no issues so no settings in the controller have been touched. Same applies to dc2dc charger, it won't charge.
Any advice would be much appreciated.
Thanks

 

[HRTKD]

Charge each cell individually with the 6 amp charger. Yes, it will take a while.

 

[mikefitz]

The BMS has detected a protection level, perhaps cell overvolts, and shut down the charge path. The cells will not be balanced with your new cell in the pack

Lower the charge voltage.

Measure each cell to determine the high cell and bleed charge with a DC load, car headlight bulb works.

Why did you need to replace a cell?

Mike

 

[Pattap]

thanks for your responses.

The BMS has detected a protection level, perhaps cell overvolts, and shut down the charge path. The cells will not be balanced with your new cell in the pack

Lower the charge voltage.

Measure each cell to determine the high cell and bleed charge with a DC load, car headlight bulb works.

Why did you need to replace a cell?

Mike

That has been happening before I have put the new cell in. The reason was that it seems one of them was charging/discharging much quicker than other and as you mentioned BMS would shut off due to too low/high voltage of that cell.

What I don't get is why the voltage difference before and after BMS. Even the cells are within acceptable voltage bracket, BMS is happy and on the Smart bms app it appears that charge and discharge are on yet still I can't charge the pack. As previously mentioned the reading after BMS is much higher. Not sure how would those factors we are discussing right now be affecting this reading. Again this is the reason my DC2DC or my solar controller won't charge the battery.

I'm charging the packs individually right now, it will be a long process. I want to top balance them once again to be on the safe side.

Still really confused about the voltage differences ..

 

[HRTKD]

This write-up found in the Resources section of the forum may help you understand what's going on with the cells and charge/discharge.

What Causes Runaway Cell Voltage?

Quite often, a cell will hit a High (or low) voltage unexpectedly and/or faster than the other cells. (On the DIY Solar Forum, this is usually called a ‘Runaway Cell’. ) The runaway cell can eventually cause the BMS to unexpectedly shut down...

diysolarforum.com

 

[Pattap]

This write-up found in the Resources section of the forum may help you understand what's going on with the cells and charge/discharge.

What Causes Runaway Cell Voltage?

Quite often, a cell will hit a High (or low) voltage unexpectedly and/or faster than the other cells. (On the DIY Solar Forum, this is usually called a ‘Runaway Cell’. ) The runaway cell can eventually cause the BMS to unexpectedly shut down...

diysolarforum.com

thanks I'll give it a read

 

[Pattap]

This write-up found in the Resources section of the forum may help you understand what's going on with the cells and charge/discharge.

What Causes Runaway Cell Voltage?

Quite often, a cell will hit a High (or low) voltage unexpectedly and/or faster than the other cells. (On the DIY Solar Forum, this is usually called a ‘Runaway Cell’. ) The runaway cell can eventually cause the BMS to unexpectedly shut down...

diysolarforum.com

I did read, good article i don't think this applies to the issue I'm facing. None of this explains why my BMS outputs higher than the batterie's voltage.

I've run some tests today. I've reassembled the pack. What i noticed is that when i put any load on the battery i am able to charge it but it will only charge with amps equal to the load e.g. i take 10 amps and BMS will allow 10amps not more.

Another thing was when i disconnected the load the voltage on BMS spiked to 16v! Just for a brief moment.

 

[HRTKD]

On a working JBD BMS, if you disable the discharge, I believe that the voltage can be "off". It's there, but not what you would expect. That's what I remember reading, but I could be wrong. But if I'm right, it sounds like you may have an internal problem in the BMS.