I have a red top optima battery like this in my truck: http://www.optimabatteries.com/optima_products/redtop/specs.php" I don't drive this truck very often so it looses power after a while. I'd prefer not to disconnect my battery and loose the memory in various electronics. so i bought a small solar charger like this: http://images.google.com/imgres?img...x-a&rls=org.mozilla:en-US:official&sa=N&um=1" It does not provide a sufficient charge to keep the battery alive. Is there a way i can measure/calculate (hopefully just with a multimeter) how much charge i need to keep my battery fully charged? I was thinking using some kind of calculation based on the voltage drop over a 24 hour period? If i only need two or three of these chargers then i might stick with the solar charger idea. If not, then i would have to resort to a trickle charger that plugs into the house. This would not be preferable since i don't park near the house.