When shopping for a solar charge controller, there are several factors you need to consider: 

• Type of Solar Panel—The type of solar panel you have will determine what type of charge controller you need since some are designed for specific types like monocrystalline and polycrystalline panels only. For example, MPPT (Maximum Power Point Tracking) controllers are designed for higher voltage panels such as monocrystalline ones while PWM (Pulse Width Modulation) controllers work with both low and high-voltage panels like polycrystalline ones. 
• Voltage of the Solar Panel—It’s important to know what voltage your panel produces before selecting a charge controller since most have specific input voltages they support. The input voltage should match that of your panel’s output voltage so that it works correctly with no issues.  
• Maximum Input Current—This is the maximum level of current that your charger can accept safely from your panel before shutting off due to the overload or overheating protection feature built into most chargers these days. Selecting one with a higher input current rating than what’s needed will ensure it works properly without any problems even when receiving higher currents at peak sunlight times…  
• Maximum Output Current—This indicates how much current can be delivered from the charger at any given time without causing it to shut down automatically due to the overload protection feature built-in most chargers these days.   The output current should be equal to or higher than what’s required by your appliances/devices otherwise it won’t be able to deliver sufficient power when needed resulting in poor performance if not shut down automatically due to the overload protection feature built-in most chargers these days.  
• Maximum Output Voltage—The maximum output voltage indicates how much voltage can be provided safely by the charger at any given time without causing it to shut down due to the overvoltage protection feature built-in most chargers these days.   This should match what’s required by your appliances/devices otherwise it either won’t work properly or may lead to serious damage if not protected properly.   
• Temperature Compensation –Some controllers come with temperature compensation features that adjust their settings based on ambient temperature conditions making sure they provide optimal performance regardless of changing temperature conditions.