Maplin used to do simple cheapish solar trickle charge systems about A4 size.
Main drawback; just the one inverter, so any shade or physical overlap of any single solar cell meant zero output.
Maplin might have better systems now,
or,
try the obvious online suppliers.
Certain you have no unscheduled current draws? Light in glove box permanently on?
Maplin used to do simple cheapish solar trickle charge systems about A4 size.
Main drawback; just the one inverter, so any shade or physical overlap of any single solar cell meant zero output.
Maplin might have better systems now,
or,
try the obvious online suppliers.
Certain you have no unscheduled current draws? Light in glove box permanently on?