Maintaining charged batteries
Lead acid batteries gradually lose their charge when not in use and, if left in a prolonged discharged state, permanently lose capacity as the sulphate hardens. Small solar modules can be used to provide a “trickle” charge that both maintains the battery in a charged state and protects the battery's capacity and useful life. This does not require a regulator as the power used is low enough not to over-charge the battery. The 5W AKT-5-M module indoors near a window would be suitable for a normal car battery.