A reliable, secondary source of power to account for consecutive days of bad weather doesn't need to be "on-grid." Most robust off grid setups that I've seen i

A reliable, secondary source of power to account for consecutive days of bad weather doesn't need to be "on-grid." Most robust off grid setups that I've seen involve the use of a backup generator. For anyone considering an off grid mobile office in a van or other vehicle. When the sun isn't cooperative for too long and I find my storage battery being depleted too low, I simply start my engine and start charging the battery using my 12V DC cigarette lighter port. I have 200W of solar feeding a 100Ah 12V battery with an MPPT charge controller and I thought I had calculated enough redundancy to handle up to a week of bad weather, but end up using my alternator to charge when the sun is unreliable more often than I thought I would. PS: Are you using a PWM controller or a MPPT controller? The latter can increase efficiency by up to 30%.