As seems to be the topic of the month, I'm having issues with my VW Caddy batteries. It has a rear entry ramp and SpaceDrive 4-way joystick amongst other adaptions. I've been trying to drive it at least once a week, despite not having anywhere I'm allowed to go, since March 2020. Anyway, this morning I could tell as the ramp descended that the main battery was flat. It wouldn't start at all and then the suspension and ramp were down. At least the ramp can be manually moved so the car is locked at least, but now I'm thinking about charging solutions.
Firstly, is it okay to do a normal jump start to get the diesel engine running so it can start recharging? I have an AA battery conditioner (https://www.argos.co.uk/product/7604351) which I think I can run from a weatherproof socket to under the bonnet via my letterbox about 10M away, across a public footpath with a cable protector and some hi-vis tape. It wouldn't be on for more than 12 hours during the day once a week I'd guess, as I don't think leaving it permanently connected is a good idea.
Where it gets more complicated (because I'm not clued up about these things) is the secondary SpaceDrive battery. It gets replaced every two years (as the servicing company insist it must be) but is now overdue a replacement. I believe it's a Li-Ion unit, and by the replacement cost I suspect it's coated in 24 karat gold. It probably doesn't need replacing I'm sure and this morning the joystick was responding correctly so it's fine at the moment. I do worry about it a lot though, with it having my life in its hands every time I drive. Anyway, on the SpaceDrive module in the back of the car it has a button that can change the SpaceDrive battery from 'drive' to 'charge' mode. My interests relate to how this is likely to affect the AA charger and main battery if I hook them up and switch the SpaceDrive battery to charge mode. I have no technical information on how the two batteries are connected, if they are. A web search has given no clues as to how SpaceDrive works in this respect.
I'd be grateful for any advice.