Hi, if I connected my spare Victron 100/50 MPPT by the PV (solar input) to my cars 12 volts, via my towbar, in theory my MPPT should act like a DC to DC charger and charge my lead acid leisure battery in my caravan. I am just curious. Any reason why this would not work? Would the cars battery/alternator amperage be a problem? I have asked AI many many questions and AI reports as long as cables are fused correctly all is good.
This would not work in your case as the MPPT does not boost voltage. The input voltage has to be 5V higher than the battery voltage to start charging. This will never occur from a 12V car system.