The DC under-voltage warning comes up each time the inverter is powered up or restarted. It is caused by an architectural timing issue in that when the unit powers up, the battery voltage check runs before the battery voltage calculation is complete resulting in an incorrect voltage being reported and hence prompting the warning. The warning auto clears in the latest version but is still logged in the warning log. It is a somewhat a nuisance but is nothing to worry about unless it persists. It will be fixed in future releases of firmware.