paralleling unparalleable Growatt inverters

[tfb]

Hi there
Current set up
1 string of cells to one Growatt SPH5000 with 2 x Growatt 6.5Kwh batteries
another string of cells to another growatt SPH5000

Growatt tell me that the version of SPH5000 I have can't be paralleled.

What I want to end up with is each inverter with it's own battery - giving me 6Kw of discharge. But it I move one battery over I will end up with situation of one battery discharging to charge up the other and then vice versa.

Looking at the Growatt Modbus protocol I can see registers for min/max temp for battery charging. What I am considering is changing these values every hour or so on each inverter to flip-flop which battery can be charged. The other option is a register to enable/disable AC charging

Can anyone see any problems with this or have a better idea?

TFB

 

[connerian]

Hi, I have a very similar setup and the way I do it is by running my own program which checks the state of the inverters and shuts 1 off for a few seconds to interupt the discharge of 1 inverter into the other (switch it to grid mode with zero discharge power rate covering the current time, then back to normal by switching off the time slot).
This happens if 1 of the inverters starts charging off the other. Thankfully there is usually at minimum a few minutes before that starts to happen, so the setup works well.
Obviously there is still a trickle lost over the day, but it's neglible.

My program logs into the growatt site to authenticate then makes calls to their API (same as their site uses) to get the data and issue commands.

I wish there were a few more settings that could be controlled around telling the battery when it can charge from excess load or not.
If I could get faster updates from the inverters via a direct setup, rather than the 1 minute updates currently, then I could controll it a lot better, -that's my next challenge.