need help with my setup, Growatt and LG Chem Lithium Ion batteries

[Milko]

Hi all, new to the forum here.

I just purchased a SPF-6000T-DVM-MPV 6kW Growatt inverter, everything looks awesome so far and I am already installing the inverter at home.

I am wondering if you guys can guide me with the BMS selection, (if I really need one), I am wondering which BMS would work with the inverter based on the batteries I have. My current battery setup is as follow.

I will be using 10 Lithium Ion battery modules, (LG CHEM MB 12S 44V 20AH 880WH, each module have 12 Lithium Ion cells in a 12S configuration with an output of 20AH and 880WH. The 10 modules are connected in parallel having a total output of 200AH and 8.800WH. I am well aware that this is not the optimal batteries for my inverter but I already had these modules around for a different project and would like to give them a try.

Can I connect the batteries to the inverter without a BMS? Is there a BMS you guys know that can work fine with the inverter and good for this battery configuration?

I am building this setup to give power to my house when the grid is down, will be using a gas generator when batteries need to be charged and grid is not able, next step will be to add a solar panel set on the roof to keep batteries charged when needed without the use of the grid.

Thanks!

Milko Migneco

 

[sunshine_eggo]

Can I connect the batteries to the inverter without a BMS?

Yes. BMS connection with inverter is only required if you configure the inverter for lithium. If you configure it for Lithium, your battery must communicate with the Growatt.

You may install ANY suitable battery without BMS communication. You simply set custom charge voltages. Your 12S configuration is at the absolute bottom end of the voltage ranges for this inverter and will likely perform suboptimally compared to the proper 14S configuration.

Is there a BMS you guys know that can work fine with the inverter and good for this battery configuration?

No. None likely exists.

You will need 10 12S 3.7V BMSs - one for each 44V module. Something like this. Expect to pay $75-100 each. Failure to protect each and every module individually with its own BMS runs the risk of 1) Best case - ruining one or more modules, 2) worst case - burning your house down.

You should also NOT charge your battery to 4.2V/cell as that will dramatically shorten its life. Consider a peak charge voltage of 4.05V/cell. You will lose 10-20% of your capacity by doing this but will multiply your cycle life by 4-10X

IMHO, your chosen battery configuration is about as worst-case as it can get. Just because you have something that you perceive it will work doesn't mean it's a good idea.

Good luck.

 

[billyblacc]

Hi Guys,

Was just about to ask for my own problem but I came across this topic and checked if it applies to mine - not really, but it sparked my interest in case of charge voltage not exceeding 4.05V/cell according to your advice @sunshine_eggo. Lithium-Ion cells would nominally work on that voltage, so what's the reason to drop it to 4.05v/cell?

 

[sunshine_eggo]

Hi Guys,

Was just about to ask for my own problem but I came across this topic and checked if it applies to mine - not really, but it sparked my interest in case of charge voltage not exceeding 4.05V/cell according to your advice @sunshine_eggo. Lithium-Ion cells would nominally work on that voltage, so what's the reason to drop it to 4.05v/cell?

Did you read my post?

You should also NOT charge your battery to 4.2V/cell as that will dramatically shorten its life. Consider a peak charge voltage of 4.05V/cell. You will lose 10-20% of your capacity by doing this but will multiply your cycle life by 4-10X.

Non LFP/LTO chemistry has notably lower cycle life.