Evening Everyone. How do I calculate the size of power bank (within budget) that will run a small heater. Also what type of heater does everyone use. I have a small 5 fin oil filled radiator that I could use or a small eclectic one that I use when on EHU. Its just for evenings to take the chill out of the van. I have a day van that I occasionally sleep overnight in so I don't have a leisure battery or diesel heater. Any advice or alternative solutions welcome.