Yes, you can replace batteries in solar lights. In fact, it's often necessary to do so in order to keep the lights working properly. Solar lights rely on batteries to store energy during the day so that they can provide light at night. Over time, the batteries will lose their ability to hold a charge and will need to be replaced. Depending on the type of solar light, you may be able to simply replace the batteries yourself. In other cases, you may need to contact the manufacturer or a qualified solar technician for assistance.