The great majority of direct current (DC) battery systems operate at 12, 24 and 48 volts. It is recommended to use 12 and 24 Volt solar panels in these systems as they provide the proper voltage to charge the batteries eliminating the need to step down the voltage. The solar panels can be paired in series to match the system voltage; for example, 4 12V panels or 2 24V panels can be connected in series to supply power to a 48V system. The solar panels in this section can be as small as 5W and are available in increments up to 140W. Only larger panels include cables, smaller panels have a junction box in the back for connections. Some of the more common applications include street lighting, recreational solar systems, beacons and marine buoys, telecommunications systems, water pumping, signage, RVs, boats and remote cabins. With the exception of the 5W solar panels is always recommended to use a charge controller between the batteries and solar panels. The charge controller will protect the batteries from over-charging.