Solar chargers. For those expecting some miracle for those panels, try this. Figure you have 1/2 run down a 100 amp hour battery and need to regain 50 amps. Look at the amp output of a solar panel and divide that into the 50 amps you need to recharge the battery to see how long with will take. Remember, for the longest battery life, a battery needs to be fully recharged shortly after use.
The 15 watt 12V solar panel in the Harbor Freight catalog puts out 1.25 amps which would take 40 hours of sun exposure to recharge the 50 amps you need to recover the battery.