The charging efficiency of solar lamps depends on their geographical location, angle to the sun, the weather and the amount of sunshine. Lights charge more effectively in summer than in winter due to longer days and brighter sunshine. In some areas, there may be insufficient hours of sunshine on a winter day to recharge a light.
Panel Condition and Position
To convert light into electricity, the solar panel must have an unobstructed view of the sky. The number of photons falling on the panel decreases when dust, mold and shade obscure the surface, decreasing the charging capability. Cleaning the panel and repositioning it may improve performance.
Most solar-powered landscape lights contain nickel-cadmium batteries. NiCad batteries suffer from "charge memory," meaning that if they receive a series of low charges they may adapt and be capable of holding only that amount of charge in the future. They also need replacing after about two years. Faulty batteries cannot store electricity and prevent the light from recharging regardless of the amount of sunshine it receives.