1. if I am in a fixed location such as a star party easy 12v car battery and inverter, I keppy my batteries I change every three years from my Renault Grand Scenic.
2.
https://www.amazon.co.uk/Celestron-1...c=1&th=1&psc=1
3.
https://www.widescreen-centre.co.uk/...tery-pack.html
Number 2 also ids a superb one in case of a power cut