What Is a Charge Controller?

The charge controller is a type of automatic charge and discharge control device installed in most solar power generation systems in order to protect the battery and prevent overcharge. Its most basic function is to cut off the charging current when the battery is full. The characteristics are different, so the charge controller used should be selected according to the type of battery.

The solar control system consists of solar panels, batteries, controllers and loads. The system block diagram is shown in the figure.

1.When the battery voltage is under normal conditions, the switch circuit controlled by the microcontroller is turned on, and the solar battery is charged to the battery; when the battery voltage reaches 13.2v, it is in a floating charge state; when the battery voltage is higher than the set overcharge At the point of 14.5v, the charging circuit is short-circuit protected at this time, and the charging is stopped; when the battery voltage drops to 13.5v, the normal charging state is restored.

2. When the battery voltage is lower than the set over-discharge point 10.5v, the output controlled by the single-chip microcomputer is cut off, and the load has no output; when the battery voltage reaches 12.4v, the single-chip control output circuit is turned on, and the load over-discharge is restored at this time normal.

3. Display circuit. This controller uses two two-color LDE light-emitting diodes to display the charge and discharge status. A lights up red for normal charging: B green lights indicate that the battery is fully charged; C red lights flash when the battery voltage is too low or the battery is not in good contact. The display of two two-color LDE LEDs is very intuitive and brings convenience to the user.

4. Temperature compensation. The capacity of the battery changes with temperature. As the temperature increases, the capacity of the battery will rise, and as the temperature decreases, the capacity of the battery will decrease. If the charge-discharge current remains the same, the corresponding charge-discharge rate will change. Different charge-discharge rates correspond to different over-charge and over-discharge points. Therefore, temperature compensation should be used to protect the battery. According to the standard temperature compensation range is -3 to -7mV / / knot, we take the intermediate value-5 mV / / knot. Because the thermistor MF58 has an approximately linear relationship between -5 ~ 45 , temperature compensation can be achieved. When the ambient temperature changes, the resistance of the thermistor changes with the temperature. The single chip computer protects the battery by sampling the temperature parameters, comparing the sampled value with the voltage value stored in the single chip, and properly controlling the charging voltage and discharging voltage of the battery.

5. The charging method adopts pulse charging, which has the effect of desulfurizing the battery and the function of inhibiting the sulfurization of the new battery. ^[1]