JDB BMS not balancing? Battery has reset on occasion.

[solarstevec]

This forum has been so helpful in my research and I finally joined after having set up my first system. Thank you all so much in advance! In the (van) system that I didn't personally build: a 200ah diy lifepo4 battery with JDB 4s 120a BMS. Hooked up to an Epever Triton 3210n mppt and 225w pv.
I first noticed problems this spring. The battery AND mppt would occasionally reset for a millisecond, causing my fan to shut. I've only seen it happen twice and unfortunately have never been staring at my BMS app. My mppt could certainly have problems, but this post is to find out if my BMS is bad, as I'm seeing weird behavior when everything's working like normal. Please see photos.
I see a "cell overvolt" alarm on when it shouldn't be (it's constantly being triggered like this, even when battery isn't full). I often see cell 1 being either way higher or way lower than the test, but not even being balanced. I've tried lowering the start voltage and delta - no help. Then all of a sudden it'll be quickly back in line with the rest. I also noticed today that voltage is up resting around 14v once fully charged and no longer charging - worried if that's too high. There are probably other weird things I'm forgetting, but this seems like enough. Is it toast? Seemed to work fine for the first couple years.
Thank you!

 

[42OhmsPA]

Looks like an out of balance pack to me.
I'd adjust charge voltage on the epever to ~3.45v/cell and let it balance as long as possible. You're not getting much additional capacity at the top of the knee anyway.
Other options are using a bench power supply and bringing the low cells up one at a time or a resistor / light bulb and bringing the high cell(s) down.
It took one of my JBDs a few days to balance some old cells.

 

[mikefitz]

I don't think you have serious issues.
Lower the charge volts , boost volts, in 0.1 volt steps until you no longer get cell overvolt shutdown, perhaps down to 13.8 volts if necessary. Set float volts to 13.5 volts.
The random effects may be due to connection issues around cell 1. Check the BMS sence lead, buss bars and power cable. Ensure correct torque on buss bars.
Often a picture of the battery helps the discussion

 

[solarstevec]

Okay, thank you both so much. I've never opened the battery before, nor configured the Epever (requires a serial connection I don't yet have). Got my homework cut out for me!

 

[42OhmsPA]

Okay, thank you both so much. I've never opened the battery before, nor configured the Epever (requires a serial connection I don't yet have). Got my homework cut out for me!

Do you have the mt50 for the epever? You can change settings with it if you do.
You shouldn't have to open the battery at all unless you want to check the BMS connections.

Edit - looks like the Triton can be programed directly from the unit using the buttons.

 

[JJJJ]

Was a top balance performed?

 

[solarstevec]

Do you have the mt50 for the epever? You can change settings with it if you do.
You shouldn't have to open the battery at all unless you want to check the BMS connections.

Edit - looks like the Triton can be programed directly from the unit using the buttons.

Duh me! I saw a PSW (password) required thing, but never actually tried a blank one. I'm in.

I don't think you have serious issues.
Lower the charge volts , boost volts, in 0.1 volt steps until you no longer get cell overvolt shutdown, perhaps down to 13.8 volts if necessary. Set float volts to 13.5 volts.
The random effects may be due to connection issues around cell 1. Check the BMS sence lead, buss bars and power cable. Ensure correct torque on buss bars.
Often a picture of the battery helps the discussion

Looks like anything over 13.6 would trigger the alarm for cell 1. The BMS still doesn't appear to be balancing as it "should" given my parameters, but I'll leave it like this and keep an eye on things. I'm guessing the BMS connections are funky.

Was a top balance performed?

No idea. I didn't build it and have never taken it apart. Guy who did didn't make it easy to pull out. Hopefully it won't come to that ?

 

[Bob B]

The JBD BMS has low balance current .... That is the reason so many people are recommending trying to hold it around 3.45 V per cell for as long as possible. It may take it a long time to balance.

Yours is set to start balancing below 3.4 .... that could be a problem over time also. Trying to balance below the knee could cause cell imbalance.
I have set mine to balance at lower voltages on a temporary basis if the same cell stays high at the lower voltages ... but I would only do that on a temporary basis.

 

[solarstevec]

The JBD BMS has low balance current .... That is the reason so many people are recommending trying to hold it around 3.45 V per cell for as long as possible. It may take it a long time to balance.

Yours is set to start balancing below 3.4 .... that could be a problem over time also. Trying to balance below the knee could cause cell imbalance.
I have set mine to balance at lower voltages on a temporary basis if the same cell stays high at the lower voltages ... but I would only do that on a temporary basis.

Hey thanks Bob. That's from me tweaking it only recently. I'll change back to 3.4.

When you say "hold around 3.45" - does that mean I shouldn't let it discharge, or just not charge above that? Living with the thing, got a fridge etc...

I was aware of the slow balancing.. I just didn't understand why it wouldn't even attempt/display "Bal" when clearly it needed to be. Perhaps at higher deltas it doesn't even attempt (?). Other lower-voltage cells would display "Bal" while cell 1 was triggering over voltage alarms but apparently not being balanced. Cell 1 - always be the highest while charging and lowest while discharging.

 

[Bob B]

The longer you can keep the pack in the 3.45 to 3.5 V per cell range .... the longer the BMS will have to accomplish the balancing.

There are also ways to manually bleed off that high cell .... a search should turn up some results for how to do that.

 

[740GLE]

balance all the time (not just when charging) cells are above 3.4 and just keep the pack at a high voltage for a few days. Your setting already show this so now it’s just a matter of keeping it at a high state of charge.

Or active balancer.

Our 460ah 12v pack sits idle 90% at or near 100% charged of the time, it still sees 3.4v each day for as long as the sun is shining. That time allows the small balancer to do its magic.

 

[Alkaline]

https://www.amazon.com/Cywhrvzsf-Equalizer-Balancer-Equalization-Capacitor/dp/B09G74WDN5

install and enjoy life.

 

[solarstevec]

Hey guys, thanks again.

Decided to pull out and learn how it's put together...
Cells balance when disconnected, not sure if that affirms anything (?).
Looks like my guy zip tied + glued the BMS to the lid of the battery box. Makes things tricky.
Everything looks clean except for some residue on one of the blue wires, altho I don't measure any resistance and assume it's fine.
No way to measure torque at the moment.

He said he didn't top balance because the cells were all within 1/100th V of each other.

I decided to order that active balancer. Guessing it'll help with my isolation manager's high current too. I'll have to guess on the torque when installing... hopefully I'll be able to get in there with a wrench ?

I'm still suspicious of my MPPT because I saw it power cycle while noticing my battery reset anomaly. But that's for another day.

 

[solarstevec]

https://www.amazon.com/Cywhrvzsf-Equalizer-Balancer-Equalization-wCapacitor/dp/B09G74WDN5

install and enjowy life.

I've tried two of these and they don't help. When I'm above the knee the delta starts to climb, even when charging with low current. They don't seem to balance any quicker than my passive bms. I'm sure top balancing would help, although getting my battery back out is such a pain and I'm not sure this warrants it (?). Seems like my only option is to keep my float charge low. I'm all ears if anyone has other ideas. Thank you all!

 

[mikefitz]

If you can access the cell bussbars, then using a suitable DC load, ( I use a car headlight bulb with cables to make simple probes), apply across the high cell whilst monitoring the BMS status. ( under a low charge condition as shown in the last capture).
Apply the load for several seconds and review the voltage drop. Adjust the duration as needed.
Repeat for the highest cell. Once you get the differential to around 40 mv, let the voltage increase to over 3.50 and continue the manual balance if needed.

 

[740GLE]

I've tried two of these and they don't help. When I'm above the knee the delta starts to climb, even when charging with low current. They don't seem to balance any quicker than my passive bms. I'm sure top balancing would help, although getting my battery back out is such a pain and I'm not sure this warrants it (?). Seems like my only option is to keep my float charge low. I'm all ears if anyone has other ideas. Thank you all!
View attachment 173081View attachment 173082

How long do you leave the balancer connected? All the time, or only when you’re above 3.4v

For my 4s I turn on the haltec balancer only above 3.4v and it will take a delta of .080v down to single digits in a mater of minutes..

 

[solarstevec]

How long do you leave the balancer connected? All the time, or only when you’re above 3.4v

For my 4s I turn on the haltec balancer only above 3.4v and it will take a delta of .080v down to single digits in a mater of minutes..

Always connected at the moment.
Seems like my passive BMS does things that well too. Something like a mV every 10-20 seconds...Is that what I should expect?
Perhaps what I'm dealing with is acceptable... I don't know. Things balance out when charger is removed and it's back at 13.3. Thank you so much.

 

[Alkaline]

I've tried two of these and they don't help. When I'm above the knee the delta starts to climb, even when charging with low current. They don't seem to balance any quicker than my passive bms. I'm sure top balancing would help, although getting my battery back out is such a pain and I'm not sure this warrants it (?). Seems like my only option is to keep my float charge low. I'm all ears if anyone has other ideas. Thank you all!
View attachment 173081View attachment 173082

You need to let the cells get up to 3.6v they don't work unless cells are high up in the upper range.

 

[solarstevec]

You need to let the cells get up to 3.6v they don't work unless cells are high up in the upper range.

That doesn't make any sense. That's over-voltage range. Their Amazon listing says "1.8 V-4.5V" and 0-5.5A depending on imbalance. I'll try messaging them again, will update if I find anything useful.

 

[Alkaline]

3.65v is the limit

 

[solarstevec]

3.65v is the limit

I'll have one cell rise above that while the others are low, and the BMS goes into overvolt shutdown. I was hoping the balancer would prevent that. It won't. The seller has been absolutely worthless but no point in returning after all the work I did to install. I think I'll just keep my charge limit and float charge low, since accessing the battery is a real pain. At the least, it helps the BMS balance things quicker when it does shutdown.

 

[Alkaline]

The balancer will not stop the shutdown but it will help balance the cells faster than the bms' built in passive balancer.

 

[solarstevec]

3.65v is the limit

Right, but because mine are imbalanced, one will be over that (and trigger shutdown) while others are much lower.
I'm going to try the @mikefitz method above...