wrote in message

......then what I did was get a
smallish solar charger, and keep it hooked up as a trickle charger all
the time. That works well for me.

If you know, or know someone who works for, a VW dealer, that could be a
good source ( i.e., $0). Every new VW comes off the transport at the dealer
with a small solar charger wired to the battery and suction-cupped to the
inside of the windshield.