Way late on a response but here is an update on my Growatt SPF6000TDVM. The system is up and running and I've had 3 blissful weeks of continuous operation finally. The Growatt is paired with a DIY 48V 16S 120 Ahr LFP battery pack operating with a 150Ahr Daly Smart BMS and a 2 kW solar array. I use the system only to run my well pump and it is also intended to provide emergency power eventually (we live in hurricane alley south of Houston).
The Growatt SPF6000TDVM is incredibly inexpensive but it has its limitations. Long story short is it will not handle what I consider "nominal" behavior from a battery pack - namely if the battery shuts down either because of under voltage or over voltage. I had both happen to me as I sorted out issues with one poor behaving cell in my 16S pack.
The first issue was with a low voltage on the battery pack. The lower capacity cell would hit the “low cell voltage” set point on my BMS and the BMS would do the correct thing and isolate the battery pack. The inverter would stop inverting and throw a low battery voltage fault. At the time this happened, I was still figuring out the Growatt, and I had not enabled the “switch to grid power” when the battery voltage goes low. I do note if you do not have grid power, well you don’t even have that option. So what would happen is the battery pack would eventually enable when the offending cell voltage rose about the cut-off voltage. And since the inverter DOES NOT stay in fault mode (this is the first major short-coming of the Growatt inverter) , the inverter would then do its thing and start inverting, and the cycle would repeat. Well this happened in front of my eyes for about 3 or 4 cycles, and my main inverter board put on a very entertaining fireworks display that include loud pops and lots of magic smoke! Now mind you I had not figured out all of this at the time it happened.
I bought my Growatt from Signature Solar (
https://www.signaturesolar.us/) and they are great – they sent me a replacement set of boards at NO COST, since at this point I was just thinking the inverter crapped out. They stand behind their products and they took care of me. The Growatt unit is relatively easy to work on and I got the two boards replaced, turned it on, and I was back in business. This time I made sure the “switch to grid power” was enabled if the battery went low.
So now the fun in the other direction – This time it was a high voltage issue. The inverted would shut down during charging when the same low performing cell went above the “high cut-off voltage” set point and the BMS isolated the battery. It would go into a “high voltage” fault since the battery was disconnected and the array was sending all that glorious solar energy to the battery. But that fault state is "soft" (like with the low voltage fault this is the second major shortcoming of the Growatt inverter) and the unit will try to restart charging if the battery voltages drops below the “maximum voltage” set point. When the offending cell voltage would drop (like LFP cells do after charging is removed), the BMS would revert to enable, and the cycle would repeat. After about 5 cycles of doing this, my inverter main board promptly blew magic smoke again from several components on the PCB (less than the last time but still fatal).
So now I was finally figuring out I had one lower capacity cell in my 16S battery pack. I called Signature Solar, shelled out $250 for another set of boards, got them installed, and fired the unit back up. This time I set up inverter operation well inside of the published limits for LFP cells (2.5 V low and 3.65 V high). I set the “low voltage switch to grid” set point at 49.2V (3.075 V/cell) and the high voltage end of charge to 54.6V (3.4125 V/cell). I’ve been tweaking a bit on those two set points (plus the float voltage), to try and ensure I get 80% capacity out of my pack whether it is a bright sunny day, or something less.
So I’m up and running now and the 2kW system is performing well. Except for 2 exceptionally cloudy days, it’s been providing all of my well-pump power. I will say the inability to survive what I consider to be routine behavior of an off-grid solar power system (battery disconnecting due to low or high voltage), is a major short-coming of the Growatt LF series. You will always have to be checking your system as it ages to make sure it does not get into either a low-voltage or high-voltage situation because if it does, the unit will fail. I am fortunate that I have reliable grid power, but others using this unit as primary power will have pay close attention. I will say, the $1200 cost (roughly 1/5 of say a Sol-Ark 8K), may make this worth the pain for many folks (myself included at least for now).