Solis/Pylontech battery charge/discharge different when forced

[Sunrise42]

Hello, I'm new to both solar, batteries and this forum so I hope I have the right place to post my question. I'm in the UK.

I have been benefitting from a large solar array via Solis inverters and Pylontech batteries. They are working well. Recently I swapped to a utility tariff which has periods of cheap imports and high exports so have been experimenting with force charge and discharge at the advantageous times; again all is working well but I've noticed one anomaly:

The inverter dedicated to the batteries is rated at 3kw (Solis RAI-3K-48ES-5G). All settings are as set by the installer.
When charging from solar the rate (+/- a few watts) is 3.3kw
When discharging at max for house consumption the rate is 3.0kw.
When charging from the grid the rate is 2.7kw.
When discharging to the grid the rate is 2.6kw.

My question is: why the lower rates when charge / discharge is forced from / to the grid?

Thanks.

 

[SeaGal]

Welcome!

Charging from Solar will always be greater (especially when we have nice sunny days like today in East Anglia), as that charge is done from DC-DC and not limited by any AC inversion and/or the limits of the Solis output circuitry.

Discharge from the Solis when from battery alone is max of 3kW, but that will depend on battery voltage. When the battery voltage is lower than fully charge it will be a bit less. As you have Pylontech batteries, these are only 15, rather than 16 cell, so will have slightly lower voltages than some of us on here.

With regard to the other values; 2 thoughts...

a) Where / how are you measuring them?
b) What charge and discharge battery currents do you have set on the 'time-of-use' screen of the Solis. That is the screen where you set the charge/discharge from grid times?

 

[Sunrise42]

My apologies for taking so long to reply.

The reason for the difference was the (presumably default) settings on the Solis inverter. It was limiting the charging and discharging current to 50amps. I've checked with Solis and they say a maximum of 60amps is permissible with this inverter, changing the 50 to 60 for both charging and discharging has unified the charge and discharge rates.

Mystery solved.

 

[SeaGal]

My apologies for taking so long to reply.

The reason for the difference was the (presumably default) settings on the Solis inverter. It was limiting the charging and discharging current to 50amps. I've checked with Solis and they say a maximum of 60amps is permissible with this inverter, changing the 50 to 60 for both charging and discharging has unified the charge and discharge rates.

Mystery solved.

Good that my thought (b) was the one
FYI; max charge rate is 62.5A