There should be no problem with charging the car battery in-situ from an external DC power source provided the charging voltage is limited to 13.6V and the current is limited to less than 2A.

To be really safe, connect the charger negative to the engine block and the positive to the battery positive.

Joe

Why is that "really safe"?

More specifically, why would it be more "really safe" than either (a) charging directly to the battery terminals, which seems to be equivalent with an intact car charging circuit or (b) disconnecting the battery from the car systems entirely, perhaps with a maintainer or another battery keeping the on-board systems energised, which ought to avoid any impact of the chargeing on the car systems?

(As above, I am not discounting the possibility of some superfluous built-in novelty gotcha in a 2022 we-have-the-technology car, but I wouldn't know what it would be. Perhaps "coding" authentication of the battery to the cars systems might be a complicating factor?)

Edited by edlithgow on 10/08/2025 at 01:57