There are two ways of using solar energy, the direct consumption and storage.
This is the difficult way, because the sunlight strong fluctuations, the high open circuit voltage and the weak or non constant electric current lacks of the necessary condictions for many consumers. Because solar panels always provide DC voltages a AC conversion is mandatory.
Caching offers several possibilities:
For storage in batteries can happen directly with a charger or a solar charge controller.
You can connect solar modules directly to solar-rechargeable batteries. but you give up the protection against surge / overload. This leads to critical or hazardous conditions not only for the battery, but also for humans.
Simple chargers provide protection for the charging battery. A protection against deep discharge also ensures long service life.
Here is a selection of protection functions:
Overcharge protection, discharge, reverse polarity protection of the module, load and battery, reverse polarity protection by internal fuse, automatic electronic fuse, short circuit protection, overvoltage protection at module input, open circuit protection without battery, reverse current protection at night, overheating and overload protection, battery overvoltage shutdown…
The result is a waste of power, such to reconsider the cost / usage ratio of a cheap charge controller.
Although many chargers are called "solar", those dispose of at least one function which makes a difference: the MPP tracking. In order solar modules to work, they are usually regulated by a so-called MPP-tracker (MPPT), to set the voltage to the required value. The MPP Tracker varies the current drawn by a small amount, calculates in each case the product of current and voltage, and provides a current value for a higher performance. This iterative process is constantly guided by a microprocessor so that is also present in varying exposure conditions (factor> 10 between the cloudy sky and sun) is always operating in the maximum power point. Performance improvements of about 20% are realistic, making possible cost savings in the module selection or shorter load times.