Is this normal?

[D. Abineri]

I am using a Growatt SPF 6000T dvm invreter and a 48V battery of lifepo cells.

I am guessing that I am missing a setting somewhere that might avoid the following behaviour.

In the afternoon sun when the battey reaches 100% SOC and is about 55V, I get a "03" (Battery overcharged) error and the inverter beeps for a while and shuts off the solar input and begins using the battery to feed the load. Then the error goes away and solar begins to come in again. This repeats and gives the data I will attach.

Have I got a parameter set wrong on the inverter? I have an Overkill bms and a Nee bms running on the system to try to keep things balanced.

I am attaching a graph of this behaviour in the hope that it helps someone to clue me in on what is going on.

Thanks

 

[sunshine_eggo]

First, all connections should be checked for proper torque and quality - crimps, no shrink caught under connections, etc.

Second, what is happening with the cell voltages reported by the Overkill?

My guess would be that you have one or more cells hitting high voltage cut-off. When this happens, the MPPT voltage typically spikes briefly before it can completely clamp down on the charge current.

Are you seeing protection events in the BMS?

Recommend you set absorption to 54.4V and float to 54.3V. Set the NEEY to balance at and above 3.40V even if not charging. Make sure no balance occurs below 3.40V as that can undo a top balance.

The battery just likely needs some time at elevated voltage to ensure it gets top balanced.

 

[Brett V]

What are your Growatt settings? What about the BMS settings?