Portable solar panels work by capturing sunlight and converting it into useful electricity through a device called a charge controller or regulator. The controller is then connected to the battery, keeping it charged.

The solar conditioner ensures that the electricity generated by the solar panel is intelligently transferred to the battery in a way suitable for the battery chemistry and charge level.
A good regulator will have a multi-stage charging algorithm (usually 5 or 6 stages) and provide different programs for different types of batteries. Modern, high-quality regulators will include specific programs for Lithium batteries, while many older or cheaper models will be limited to AGM, Gel and Wet batteries. It is important that you use the correct program for your battery type.
A good quality solar regulator will include a number of electronic protection circuits to protect the battery, including reverse polarity protection, short circuit protection, reverse current protection, overcharge protection, transient overvoltage protection, and overtemperature protection.