G'day Darren,
The compact lithium car jumper starters may be your answer. Particularly the ones that come with 240vac chargers and a set of gender benders that can fit your scope, iPhone etc.
Small enough to sit or mount on the dob base and keep in glove box for emergency car starts.
Here is an example.
https://www.kogan.com/au/buy/certa-1...Q&gclsrc=aw.ds