LG 6.5KWh modules with new BMS and cells balance.

[Glock24]

Hello everyone!

I got 5 LG EM048126P3BA 6.5KWh 48V modules for really cheap. They all work but I have no way to communicate with the onboard BMS to check cell voltages and balance them if needed. Because of this I decided to get a new BMS and my choice was the JK BMS JK-BD6A17S8P as the max charge/discharge current for these modules (according to spec sheet) is 60A and they have a 2p14s configuration.
I ordered 2 units and they arrived surprisingly fast. I got one out and made a temporary test connection to one of the battery modules. I used the connector for the factory BMS thanks to the pin layout I found here:

BMS in LG CHEM ESS modules

I've just my personal measurements and drawings, but I can send it to you.

secondlifestorage.com

Of course I verified voltage on each pin before connecting the BMS. Once everything was connected I pressed the button and it came to life!

As I feared, the cells were not balanced. Most cells were within 10mV but the lowest one was 35mV lower than the highest one.

After leaving it balancing overnight the voltages are more close, bit still20mV difference.



So far the balancing has been going with the battery disconnected, would it be faster while the battery is charging?

It seems this BMS works OK, I think I'll order one for each module.

 

[Glock24]

For those with more experience, how do I change the settings? I'm trying to set 4.05V for 100% SOC voltage but it won't accept it, neither does it accept 4.2V for OVP. I see no profile for NMC so I'm using the default LiFePo.

 

[Glock24]

Duplicate.

 

[400bird]

I'm not an expert on that BMS, you may need to enter the password or turn off the input/output mosfets.

As far as balancing, it's just going to take a while. On that cell chemistry and with the slow balancing, it will get there, just be patient. I should also note that you probably don't need to stress over it. NMC has a linear voltage to SOC relationship, so 20mV imbalance is pretty close to balanced. Once you get the BMS settings figured it out, I wouldn't hesitate to put it into service and let the balance work itself out over the first week or two in service.

 

[Glock24]

Thanks for your reply. I already entered the password and I could change some other values, but not the voltage settings.

Right now I made a temporary connection and won't put it into service like that, I'll get some proper connectors first and leave it permanently.

 

[Glock24]

The BMS managed to balance the cells to 2mV difference, I disabled balancing, connected it to the SCC and the next day in the afternoon there was a 17mV difference, with cell #14 again being lowest.

Question: would leaving balancing on all the time be counterproductive?

I attached the BMS to another battery and to my surprise voltage delta was 3mV!



Coming back to the JK BMS settings... I really hope the manual included an explanation of the settings! Selecting the Li-ion profile had values more in line with NMC, I just had to adjust to my preferences.

I managed to find what most settings mean, but there are some that are a mystery to me:

* Vol. Cell RCV
* Vol. Cell RFV
* Vol. Smart Sleep
* Time Smart Sleep



Anybody know what those are for?

 

[JPilkey1]

To Glock24, I am in the same situation. I can purchase that same model for my 8K Sun inverter. Just wondering if you got you system to work OK and if purchasing one of each of the BMS that you chose for each unit was a good way to go?

 

[Glock24]

To Glock24, I am in the same situation. I can purchase that same model for my 8K Sun inverter. Just wondering if you got you system to work OK and if purchasing one of each of the BMS that you chose for each unit was a good way to go?

Sorry for the late response, I completed the system just recently as I was waiting to install some additional panels and needed bus bars and some cables.

Yes the system works great with the JK BMS. Note that I don't use communications from the BMS to the inverters, I just use the BMS as a protection device and to monitor batteries' health.

You need a BMS for each battery.

 

[Glock24]

For those with more experience, how do I change the settings? I'm trying to set 4.05V for 100% SOC voltage but it won't accept it, neither does it accept 4.2V for OVP. I see no profile for NMC so I'm using the default LiFePo.

Using the profile for "Li-Ion" as a base is the best way to go for NMC, the settings are very close to what I needed/wanted.

 

[Glock24]

Well, I found info on what every setting means and the order in which they must be set. This video contains all the info:

On a side note, I ordered 5 identical JK-BD6A17S8P and The last few days I've been installing them on my batteries. To my surprise one of the BMSes is different, apparently it's an older version. According to the app, it is HW v.11, the other ones are HW v.15



There are some items missing from the app toggles but nothing really important, maybe the current limiter would come handy.

Besides that I kinda prefer the connection style of the older BMS as I can attach the cables directly.

 

[Glock24]

Just out of curiosity, is there any firmware available for the non-inverter JK BMSes? I've only found info for the JK-PB series.