Yes you can as long as the main isolator switch is in the “on” position. This type of charging is not controlled by the on-board microprocessor since the charge current will flow direct to the battery via the main isolator switch. If an external voltage regulator is not used, there is a risk of overcharging and damaging the battery. Please also consider the accessory sockets are fused at 10A, so a current flow higher than this will blow the fuse.