Every solar panel needs a regulator, to make sure we don't overcharge the battery when it's full, and to give it everything the solar has got when the battery is low. You will probably have heard of the two types – PWM and MPPT – pulse-width modulation or maximum PowerPoint tracking. Now this might get a bit. Now if you have a panel with an open-circuit voltage (Voc) higher than about 22 Volts, then you don't have a 12 Volt panel. So if you want to charge a 12 Volt battery, there is little choice but to. Also, if your system has higher battery voltages, say 24V or 48V then a good MPPT might well make sense, because the difference between battery and panel voltages is greater, and. While we're on that topic, if you're looking at buying a solar panel that seems “too good to be true” then the simple calculation of efficiency.