The solar panel absorbs the solar energy from the sun, which is distributed in in required amount by the battery. Its power is measured in ampere-hour. The battery used in solar system is different to that of the batteries used in the vehicles. If needed the batteries can be used upto 80% or discharged.So, these batteries can also be called as deep cycle battery/solar flat/tubular plate battery. If the battery is full charged although its not a sunny day for 4 to 5 days it can function properly. It contains sulphuric acid. Though sulphuric acid does not dry, the water level in it decreases, so distilled water must put from repeatedly. At interval (3months/6months/1yrs) to put the water depends on the of place the battery is kept. The distilled water must be added so that sulphuric acid level doesn’t fall below the lower line of the battery. The life span of the battery will decrease if tap water is given, electricity is misused, if acid is spilled, if battery is moved time to time from its original place and battery isn’t fully charged. If the acid in the battery is spilled it must immediately washed out by the water or soda so that it will not harm the battery.