Solar Trickle charger

Well you don't want to go TOO cheap......and you don't want it to be just a 'dumb' trickle charger.

I'd say that 15 watts would about minimum; more if you have a LOT of batteries, and it needs to have a "smart" controller with it.

Note: IF the batteries are healthy and fully charged going in, leaving them sit unattended for 90 days or so should NOT be a problem.....IF they are completely disconnected.

I have a Deltran 15 watt charger and it is top of the line. It will keep either the house or the chassis batteries topped off if fully charged when applied. It was very expensive+- $150. If I were to buy mow, I get at least 30 watts. Google Solar battery charges and compare. For $150 I could make one from the wires and battery clips to the controller and a 60 watt panel.

I have no other personal experience, just stuff I've gleaned from the forums.

I use a 30 watt solar panel purchased on Amazon and a twenty dollar WindyNation waterproof controller. Four stage too...bulk, absorption, float and equalization.