The controller is 12/24/36/48V auto, but the of the photovoltaic panels used to charge different batteries is different. For 12V batteries, use about 18V photovoltaic panels, for 24v batteries, use about 30-37V photovoltaic panels, and for 48V batteries use 60. For photovoltaic panels around -72V, the controller wiring is connected to the battery first, and then to the photovoltaic panel. Disconnect the wire on the contrary, otherwise it will easily cause damage to the controller! ! ! Description 60A 12V 24V 36V 48V AUTO Solar Panel Charge Controller Solar PV Battery Charger With LCD Display The controller is 12/24/36/48V auto, but the of the photovoltaic panels used to charge different batteries is different. For 12V batteries, use about 18V photovoltaic panels, for 24v batteries, use about 30-37V photovoltaic panels, and for 48V batteries use 60. For photovoltaic panels around -72V, the controller wiring is connected to the battery first, and then to the photovoltaic panel. Disconnect the wire on the contrary, otherwise it will easily cause damage to the controller! ! !