BMS PROBLEM!!!

[RogerW]

Hello everyone.
I'm having some difficulties here with my solar system. I only have couple days with it and I'm new to this. I have 2 jbd 200amp bms. Each with 16 batteries. But one of the BMS's indicates charge overcurrent. And usually starts at 50% batteries capacity. So it shuts down and couple seconds later starts up again and shuts down and on. During the day it still reaches 85-90% charge. But after Sun is down switches are on But there is no discharge. Only from the other bms. So of I turn of the working bms the other ones comes on. And if I switch the other on this one shuts down. We have the 2 sets of batteries with each fuse ran through one same wire. Would that be a problem? I have no idea where to go from here. And batteries were top balanced. They actually keep balanced even when it says current overcharged

 

[sunshine_eggo]

#1 cause of issues is bad connections.

Check each and every terminal for proper torque.

Check each and every BMS lead for good crimp and torque.

Check that wires are firmly in the BMS connector, and that those connectors are secure.

Literally check each and every location where electrons may move... cell interconnects, bus bars, inverter terminals, charger terminals, etc.

Your method of main connections looks fine. those don't look like Class-T fuses, so they may not suffice.

 

[RogerW]

#1 cause of issues is bad connections.

Check each and every terminal for proper torque.

Check each and every BMS lead for good crimp and torque.

Check that wires are firmly in the BMS connector, and that those connectors are secure.

Literally check each and every location where electrons may move... cell interconnects, bus bars, inverter terminals, charger terminals, etc.

Your method of main connections looks fine. those don't look like Class-T fuses, so they may not suffice.

Thank you very much for your reply. I'll be sure to go over all terminals and connections. I'm pretty sure they are all good. The fuse that came with each bms is a 400amp fuse. We only place them together to have one wire going to the buss bar. Besides checking on that. What else can be the issue?

 

[sunshine_eggo]

Thank you very much for your reply. I'll be sure to go over all terminals and connections.

Including any crimps.

I'm pretty sure absolutely confident that they are all good because I just finished checking them three times.

When you can say the above, you don't need to check them again.

The fuse that came with each bms is a 400amp fuse. We only place them together to have one wire going to the buss bar. Besides checking on that. What else can be the issue?

Too numerous to list, and speculative. I'm sticking with my original response as it's SHOCKING how often bad connections contribute to ALL types of issues. Checking connections is always the first steps to troubleshooting issues.

 

[42OhmsPA]

What do you have your charge overcurrent set to?
How many amps are you charging with?
I had reduced mine and kept getting disconnects around noon until I remembered I reduced it...

 

[740GLE]

Can you post a screen shot of both BMS and cell voltages from the app, so we can compare the two.

 

[WindWizard]

Someone can possibly help you if you post the actual data from the BMS when it is not charging. The problem is that the BMS does not tell you why, you have to be a detective and figure out why. The BMS is doing what it is supposed to do and not charging because of some reason.

 

[42OhmsPA]

You can see faults if you connect to the PC.
I'm running 2 of the 200a and 1 300a.
I'd bet charge overcurrent is set to low in the BMS or a cell is running.

I'm in a agreements with other's, we need to see settings to assist further.

Nice build buy the way. I like those DIY bussbars. I would add a class T fuse.

Note the voltage settings in mine have been changed from factory.
If anyone has the factory JBD settings would you mind sharing them? I forget to record them before I made changes...

 

[HighTechLab]

If pack 1 BMS operates fine until pack 2 is turned on (or vice versa), my bet is that they are not at the same SOC and there is significant current flowing between the two packs to balance out the SOC difference.

Personally, I don't like that fuse arrangement on the positive terminals. A+ for creativity, but you really ought to upgrade to a real fuse holder because the fuses on their own lack much of any structure and it would be really easy to destroy the fuses if the main positive cable got pulled a bit. I've seen it happen. If you want your fuses on the terminals (which is actually a good and safe place to put the fuse), then use a BlueSea MRBF fuse/fuseholder. The MRBF fuses are rated to 58v/5000AIC

 

[RogerW]

What do you have your charge overcurrent set to?
How many amps are you charging with?
I had reduced mine and kept getting disconnects around noon until I remembered I reduced it...
View attachment 183579

I see there is one parameter set different. The one that is working has 285000 and the one displaying overcurrent I the one with 28500. Maybe that's the problem?

 

[42OhmsPA]

I see there is one parameter set different. The one that is working has 285000 and the one displaying overcurrent I the one with 28500. Maybe that's the problem?

I don't think that would do it.
(edit that would do it. My calculator malfunctioned, thanks @Quattrohead )How many amps are you charging with when the faults occur?.

I would change a bunch of settings in your BMS.
Batt overvoltage 5760mv
Cell Overvoltage 3600mv
Cell undervoltage 2600mv
Under temp 0c or warmer, make sure temp probes are in a good spot
Max charge discharge could be changed as well depending on the cell specs.
Some will consider them somewhat aggressive but they will keep your cells safe. You also want to make sure the settings in your charge controller are below the BMS limits.

You can save configuration files with the Overkill app if you weren't aware. This makes it really simple when configuring a bunch of packs.

Did you happen to catch the individual cell voltages while the faults occurring?

 

[Quattrohead]

The one that is working has 285000 and the one displaying overcurrent I the one with 28500. Maybe that's the problem?

Yep that will do it. One is set to 285 amps (too high) and the other 28.5 amps (too low)

 

[rhino]

As a side question from your pic, do you have anything between the cells? For safety you should not rely on that blue wrap around each cell alone to isolate cells from one another.

 

[RogerW]

Can you post a screen shot of both BMS and cell voltages from the app, so we can compare the two.

Someone can possibly help you if you post the actual data from the BMS when it is not charging. The problem is that the BMS does not tell you why, you have to be a detective and figure out why. The BMS is doing what it is supposed to do and not charging because of some reason.

 

[WindWizard]

Changing the parameter should correct your charging issue. I would seriously consider getting two Class T fuses to put on your positive terminals to protect your Cells.

Another item to note. Some of your BMS wires are very tight. It would be better to leave a bit of slack in the wires, so the wires don't pull out of the connectors.

 

[RogerW]

Changing the parameter should correct your charging issue. I would seriously consider getting two Class T fuses to put on your positive terminals to protect your Cells.

Will definitely order a couple of those to the US. Thank you.

 

[RogerW]

I don't think that would do it.
(edit that would do it. My calculator malfunctioned, thanks @Quattrohead )How many amps are you charging with when the faults occur?.

I would change a bunch of settings in your BMS.
Batt overvoltage 5760mv
Cell Overvoltage 3600mv
Cell undervoltage 2600mv
Under temp 0c or warmer, make sure temp probes are in a good spot
Max charge discharge could be changed as well depending on the cell specs.
Some will consider them somewhat aggressive but they will keep your cells safe. You also want to make sure the settings in your charge controller are below the BMS limits.

You can save configuration files with the Overkill app if you weren't aware. This makes it really simple when configuring a bunch of packs.

Did you happen to catch the individual cell voltages while the faults occurring?

All cells are well balanced. 0.003 different.

 

[RogerW]

As a side question from your pic, do you have anything between the cells? For safety you should not rely on that blue wrap around each cell alone to isolate cells from one another.

This is how the batteries are. What do you suggest.

 

[42OhmsPA]

I like these
Arrow Home Products 10pc Flex Cutting Mat, White https://a.co/d/dj1RUnG

 

[SeaGal]

This is how the batteries are. What do you suggest.

I trust the change of overcurrent has now fixed the issue?

My 2p worth...

1) Add some insulation between cells as mentioned above - some Perspex or mat as already suggested.

2) You may want to add some compression / restriction for bloating - there are many many threads about that on here.

3) When changing the fuses, personally I'd swap the black +ve cable for a red one, or as a minimum add red sleeving... It's probably just my ocd, but it's easy to think, having just built the thing, "Of course I'll remember that that black lead is actually positive", but in 18 months time, in the middle of the night, if something goes wrong and you need to do an emergency fix, you may not remember - then a mistake on the non-fused side of 28kWh of storage isn't going to be pleasant.