1. The battery wears out
Most solar garden lights use rechargeable NiMH cells, often AA or AAA. Over time they hold less charge, so the light gets dimmer and runs for a shorter time each night.
2. Check the panel first
Wipe the solar panel and place the light where it gets several hours of direct sun. A dirty or shaded panel can leave a healthy battery under-charged.
3. Replace with the same type
Buy the same rechargeable type and capacity, shown in mAh on the label. Alkaline cells aren’t designed to be recharged, so don’t put them in a solar light.
4. Reseal the compartment
Many solar lights have a sealed battery compartment. Reseat the seal properly after you swap the cells, or water can get in and corrode the contacts.