The equipment or appliance may need some type of voltage regulation to prevent it from being damaged. This is also a very simple type of solar power system. It consists of a solar module, a diode, and a battery. Inexpensive and simple. Diode prevents battery from discharging back through solar panels at night or during cloudy periods.
Equipment can use power from the solar modules and batteries at the same time.
The battery provides voltage regulation to the equipment. If the solar module is sized too large, where the power output of the solar module is greater than the power usage of the equipment, then overcharging can occur which can damage the battery. The charge controller allows the solar modules to fully charge the batteries, then redirects the solar module current so the batteries will not be overcharged. Inexpensive simple straight forward system. Charge controller prevents battery from discharging back through solar panels at night or during cloudy periods.