On Sun, 29 Nov 2020 08:44:48 +0000, alan_m
wrote:
snip

Just fit a diesel heater

https://www.youtube.com/watch?v=7NBMq5o_UJU

100s of listings on Ebay so possibly a popular item with electric car
owners

snip

Mate just bought one for his VW weekender van and was asking me how he
could / should power it as I think hoping he could use a small
auxiliary battery, rather than having to run the main battery down.

As it's diesel it looks like it uses a glow plug to (initially) ignite
the fuel meaning it draws about 10A to start with and then drops down
to 1A after that (for the blower fan and fuel pump).

Depending on if it actually shuts right down when up to temp or not,
then if it was on for 8 hours overnight that could all add up re the
drain on any supply battery.

Cheers, T i m