Do i need to uprate my battery when i rig a 12volt - 240volt power inverter to run multiple kit in my van?

i want to rig a power inverter into my van so that i can use 240 mains equipment when out and about. however, im guessing i need a 300watt inverter? since i will be using multiple things at the same time, laptop, light, fridge, power tools via an extension etc. (maybe even a 500w). do i need to upgrade my... show more i want to rig a power inverter into my van so that i can use 240 mains equipment when out and about.

however, im guessing i need a 300watt inverter? since i will be using multiple things at the same time, laptop, light, fridge, power tools via an extension etc. (maybe even a 500w).

do i need to upgrade my vans main battery to keep up with the extra drain?

besides running the engine every hour for 10minutes, any tips on usage times and drain times would be great also.

thanks
Jon
5 answers 5