Hi Wrenches,
I am regretting some HomeGrid Stack'd off-grid installations right now. There is a major flaw in the way these function in an error state. For those of you that don't know, these 48V batteries are stacked with a single BMS on top, covering up to 8 batteries below. Each battery module has a circuit breaker and dip switches to identify the battery communication number and location in the stack. Each BMS can be paralleled to additional stacks with communication cabling.
The issue is when one battery module goes into an error state. What will happen is that battery stack's BMS will recognize the error, and then shut down the whole stack. This cascades to the other stacks and the system shuts down - fails to deliver 48V at the output terminals on the BMS of any stack.
That is annoying, but what's even more problematic is you can't just shut off the offending battery to bypass it. You need to physically change all of the dip switches to bypass it and then reprogram the BMS to re-recognize the new module count (after taking it out of parallel). This is all very time consuming and requires the inverter system to be shut down. Even if a battery is not in an error state, you can't just turn it off. The whole system goes haywire.
Once you have it bypassed, you can hook up a RS-232 cable (Mac users need not apply) and use their software to gather diagnostics. Customer service will then want to do additional diagnostics with the battery in the stock, but that is not reasonable in and off-grid system where uptime is critical. One of the faulty modules I am dealing with was diagnosed as one of 15 cells with low voltage. The "solution" is to take it out of the stack and charge it to 100% with an external charger.
By the time I'm done with all of the diagnostic nonsense, I can almost pay for a new battery with the lost labor. Isn't the whole idea for this not to happen with balancing done automatically? It was suggested to me that it didn't get charged to 100% often enough, and that is why it happened. That isn't an acceptable reason for failure in an off-grid system.
I hate to say this, but EG4 has a far better 5kWh solution in this respect. Each module has it's own BMS. When one fails, you can simply turn off the circuit breaker and everything else continues to work. In fact, a fault in one BMS doesn't take out the whole stack or stacks of battery modules.
Back to HomeGrid. When this happens, in my mind this is an automatic RMA. They should be replacing these, no questions asked. Especially at almost twice the price of EG4. They actually want me to disassemble the case of the battery and charge it with an external charger (which I don't have) directly from the terminals that are internal to the battery case. Totally unacceptable. Whatever is inside that case is their problem in my opinion.
I am not selling anymore HomeGrid until I get satisfactory resolution to these issues. EG4 isn't perfect, but I have actually had pretty good success installing some that I sold and quite a few that consumers purchased directly. And at almost half the price, it's easier to eat the cost of a battery here and there for customer satisfaction.
Anyone have similar issues with HomeGrid?
Jason Szumlanski
Florida Solar Design Group
