Do you use a solar battery tender. If so witch one.

 

No sir, I wouldn't think they are reliable enough to give me the peace of mind I would need.

 

My father-in-law used a solar battery charger as a back-up in his RV for several years. It was never enough to meet the full load on the battery (which can be very high in a 35 foot RV) but it did help keep the battery topped-off during low-load periods.

I don't think I would completely trust it for a long storage period, but theoretically it should be enough to keep the battery topped off, versus the small drain that is always happening in these modern cars.