PV panels only provide power when the sun is shining and wind generators only produce when there is sufficient wind, which can be less than 25% of the day. Typically we store power during times of generation in battery packs for use when no generation is possible. In order to keep those batteries at peak performance, and provide long service life, a regimen of maintenance must be observed.
The main things to remember when keeping your batteries in trim is cleanliness of the terminals, proper water levels, and not discharging below the recommended minimums, which in our case is 50%. Proper charging is also important. The best “manual” I have found describing the technologies and methods of care is Bill Darden’s Battery FAQ. There is a section on sulfation, a common battery killer in improperly maintained batteries. A recently purported cure for sulfation can be found at http://www.batterylifesaver.com/. The inventor claims that by dissolving sulfate crystals, he can increase battery life and perfomance.