It only needs to be "smart" if it puts above a certain amperage.
I have a few pulled batteries for lights in my cargo trailer hooked to a pair of small 6v solar panels in series.
Bright sun gets the output around 18v at around 0.2A these used up batteries have been at it for years.
You could also set up a regular top up with a regular charger .
As the Military does with depot vehicles.
Or find the IOD (ignition off draw) fuse and pull it. That will work like the master off mentioned earlier.
