Just look at the back of your panel. They should be listing how many volts your panel should be producing. Another way is to estimate by counting solar cell count. First of all solar panels are a collection of solar cells. When the light hit them, they collectively produce voltage. Voltage production depends on environmental. Before planning to reduce your solar panel you have to make sure your panel is performing well. If it is broken and producing low voltage you'll have problems in the long run. Most experienced people know why sometimes you need to reduce your panel's voltage. But in case you are inexperienced, it is an. So amongst these four what method is the best? In my opinion, you should either use an MPPT charge controller or consider buying a compatible panel. To my knowledge, there are four main ways you can reduce the voltage of your panel and make it compatible with your equipment. They are using MPPT Charge Controller, Step Down Converter, Using Resistors, and finally.