I’m looking for a 12 volt solution (car batteries charged by solar panels) to pump water from my well, should the grid go down for awhile. Could hand pump, but a nice auto solution would be nice. Drop a hose or pipe down the well-head, pump the water up and into an outside faucet/garden hose hookup to re-pressure the house water/pump system reservoir. 220 VAC backup systems (wind, solar) to run the existing well pump are hard to find. A pressure switch would be nice, too, that stops the pump at about 50 psi. I may have a source for the pump but need more info on the pressure switch, and suitable charging power from the panels (or a windmill).
Have you thought of boat shows?
A bilge pump will operate only when the level of water reaches a certain height. You could adapt it to kick in when the water is reduced to a certain level.
Marine batteries typically are deep-cycle. Plus, many boats and yachts trickle-charge their on-board batteries with solar panels wrapped around the spars. These marine PVC's are essentially blankets with the cells woven into them; since they're for marine use, they can stand long exposure to the elements.
Food for thought!