Why sometimes the inverter takes power from the grid to charge the batteries even though "charge from grid'' is disabled.

When 1). the min cell voltage is below 2.95V,

2). the cell temp is lower than 3 degree while battery SOC is lower than 15%,

3). the battery SOC is below min SOC - 5%, the inverter will charge batteries taking power from grid to protect battery (to avoid batteries being empty).