Help with BMS Settings 280ah

[McDavid403]

Hi, I have the JBD Smart BMS 4S Lifepo4 200A BMS with Balancer. Model sp04s034 on my 4 cell 280Ah build.​

Have been charging with solar sometimes with my generator. Things were working fine until now. Am seeing one of the cells (cell 4 in my setup) have big voltage drops when a large load is running. All 4 cells would be similar and then the 4th cell would drop suddenly, for a sec then go back to normal.

Corresponding with this is the lights will flicker and the inverter will trip with any load. 400w or higher and then everything would go back to normal after it trips. This repeats itself anytime there is a large load. I have the Renogy 2000w inverter.

Any ideas? Can anyone share BMS config setting if you have a similar setup? Should I update my firmware? I am thinking it’s in my BMS. When charging on solar, I see the same behaviour on that 4th cell. It would blip and spike in voltage and then drop down to match the other 4 cells. Not sure if I need to rebalance cells.

Am calling right now with no cell service but when I go to cell coverage am away from BMS but will try to take a pic of my settings and post next time I’m in cell coverage area.

Thanks in advance!

 

[sunshine_eggo]

Welcome back. Is this the same battery as:

JBD 4S 200A BMS

And I'm not convinced the balancing function works well when the cells are a bit out of whack. It is happily balancing all 4 cells now after manually equalizing them a couple of times. The balancing function works fine, if you top balance first, and charge/discharge on a regular basis. Once...

diysolarforum.com

The defaults are generally fine in most cases. Have they changed since your prior posts?

Time to check all connections for quality, proper torque, cleanliness, etc. Sense wire crimps can loosen and cause erratic behavior.

What you describe is almost always either a connection issue, imbalance, or failing cell issue. JBD failures don't seem very common if they aren't abused with regular BMS protection triggers.

 

[sunshine_eggo]

Also, have you confirmed the voltage drop behavior you see on the BMS with a separate meter?

 

[McDavid403]

Welcome back. Is this the same battery as:

JBD 4S 200A BMS

And I'm not convinced the balancing function works well when the cells are a bit out of whack. It is happily balancing all 4 cells now after manually equalizing them a couple of times. The balancing function works fine, if you top balance first, and charge/discharge on a regular basis. Once...

diysolarforum.com

The defaults are generally fine in most cases. Have they changed since your prior posts?

Time to check all connections for quality, proper torque, cleanliness, etc. Sense wire crimps can loosen and cause erratic behavior.

What you describe is almost always either a connection issue, imbalance, or failing cell issue. JBD failures don't seem very common if they aren't abused with regular BMS protection triggers.

Yes same battery from that post. BMS settings are the same. I’ll re-check my connections when I’m back at home.

But there is something definitely off with that 4th cell. When I’m charging from the generator or on solar, that 4th cell is always triggering the high voltage shut off and is at 3.6V compared to the other cells which are just above 3. and then when there is a load drawing from the battery, that 4th cell drops and is significantly lower then the other 3.

 

[McDavid403]

Also, have you confirmed the voltage drop behavior you see on the BMS with a separate meter?

No, but good suggestion. I’ll do some further testing when I’m back at home. I might try to top balance each individual cell again as well.

 

[sunshine_eggo]

Yes same battery from that post. BMS settings are the same. I’ll re-check my connections when I’m back at home.

But there is something definitely off with that 4th cell. When I’m charging from the generator or on solar, that 4th cell is always triggering the high voltage shut off and is at 3.6V compared to the other cells which are just above 3. and then when there is a load drawing from the battery, that 4th cell drops and is significantly lower then the other 3.

If this behavior is confirmed with a voltmeter (and connections are confirmed good), you have a bad cell.

 

[Ampster]

I might try to top balance each individual cell again as well.

I would not do that until you confirm connections are good and BMS is showing same voltage as voltmeter. If cell #4 has reduced capacity it will exhibit high voltage on charging and low voltage on deep discharge. I have observed that phenomen and it turned out to be a bad connection of that cell to others.

 

[McDavid403]

It was indeed a bad connection. Volt meter showed cells were all fairly matched and volt meter was not picking up the spike in voltage for cell 4. After I tightened the one terminal which was loose, cells are back to what I was seeing before. Thanks again for your help!! What a great community!

 

[McDavid403]

It was indeed a bad connection. Volt meter showed cells were all fairly matched and volt meter was not picking up the spike in voltage for cell 4. After I tightened the one terminal which was loose, cells are back to what I was seeing before. Thanks again for your help!! What a great community!

Just noticed, the BMS had set total capacity to 252000 mAh. I never changed it but that’s what it was set to when I read the BMS config settings. I’ve changed it back to 280000 now.