Problems with Renogy Smart Lithium

[Tylopoda]

Hello all!

I may need your help.
I have three 12V 100Ah LiFePo4 Smart BMS with self-heating installed in parallel in my motorhome, connected via Modbus and monitored via Home Assistant - so far so good.

Now I noticed a strange behavior:
When I draw >180A (so 60A per battery) the battery bank shuts down, even though they are rated for 100A per battery.
After removing the modbus communication between the batteries, I was able to pull >250A before my (too small) breaker cut the power.

So it looks like the batteries are communicating with each other and acting as one battery, but the BMS is not raising the max discharge current to 300A.
Has anyone noticed similar behavior and/or have a tip on how to solve this problem? (other than not connecting them)

Thanks in advance,
Oliver

 

[time2roll]

The batteries are separate and operate independently. There is no regulation between the batteries to split the load perfectly at 1/3rd each.
Need to verify balanced wiring between each battery and the bus. All connections must be clean and tight.

If anything is out of balance one battery may supply most of the power and shut down. Then the remaining batteries do the same in a cascade.

A DC clamp meter could verify what each battery is providing to a large load. Possibly the renogy app would also do this.

A couple pictures of how all is connected may help.

 

[Tylopoda]

Thanks for your reply!

Yeah, the load is balanced between the batteries, I think it’s only the BMS which is confused. I’ve attached a log of the drawn current over the 3 batteries (with around 135A peak)


The batteries are connected via 50qmm cables. To the + busbar from the first battery and to the - busbar from the third battery (each with 2x50qmm cables)

If I disconnect the blue RJ45 cables, the bank delivers >250A. Is really weird…

 

[time2roll]

I would have to assume the modbus is telling the batteries to shut down. I would try disconnecting communication to just the third battery.

Are you using just the Renogy monitor? Sorry not familiar with Home Assistant.

Any help from renogy?

 

[Tylopoda]

Renogy answered today, but they wanted a lot of input first

But you gave me an idea: I tested the Renogy monitor.
With the Renogy BT-2 Monitor connected, I was able to pull >250A and trip the breaker.
So it looks like the Bluetooth Monitor not only provides data to the app, but also manages the battery bank.
I added a full-lane Y-RJ45 splitter and am now able to see my data in Home Assistant, pull >250A, and still have the safety features that come with the in-bank communication.

Maybe I will further re-engineer the BT-2 Module to implement this kind of management in Home Assistant, but thats a future project ?

Thank you for your help!

 

[tgregg]

@Tylopoda, How did you connect the BT-2 module to your multiple Renogy batteries? I have 2 self heating 100ah batteries in parallel with a RJ485 cable daisy chaining then together and a Renogy RMS LFPS monitor connected to the last battery's RJ485 port.

I want to replace the Renogy Monitor with the BT-2 blue tooth module and use the DC Home app but I don't want to lose the ability to put the batteries in shelf mode.

Do in need the RJ485 splitter you mentioned? Does the app recognize multiple batteries? can you see the discharge current for individual batteries?

I also have a Victron 712s shunt based monitor that I use the relay function to turn on and off charging based on SOC.

TIA