It is important to replace your old rechargeable batteries when they run their life cycle.

When you purchase your solar lights, the rechargeable batteries are often already included in the fixture. After 1-2 years (or a matter of months in some cases) it is quite normal to see their performance decline. Once you notice that the lighting time is considerably diminishing and the lights are not as bright as before, it’s probably time to replace your rechargeable solar garden light batteries.

Types of rechargeable batteries.

Most solar garden lights need between 1 to 4 batteries to work. 2 types of batteries are usually used in garden solar lights: AA size - NiCad (Nickel Cadmium) 1.2 V / 500 to 900mA
, and AA size - NiMH (Nickel Metal Hydride) 1.2 V /1000 to 2000mA.

When it is time to change the solar light rechargeable batteries, the choice of battery also plays an important part in ensuring the enhanced performance of your solar lights. Nickel metal hydride batteries (NiMH) will have up to three times more capacity than the same size Nickel cadmium (NiCd) battery, meaning they are capable of lasting longer and more reliable. NiMH batteries in your solar lights may cost a little extra but they are more environmentally friendly than NiCd batteries. NiMH batteries are more environmentally friendly because they use a dry liquid, which can be disposed of more easily. They will also withstand greater temperature fluctuations operating in temperatures ranging from -20 to 60 degrees Celsius (-4 to 140F). NiMH batteries have a "non-memory effect" which means they will continue to charge on cloudy days. The battery performance will not be diminished by these partial charges, as what can occur with lead acid batteries.

Read here about 5 Main Reasons Why Your Solar Lights Are Not Performing as Well as New.