As the input energy of solar power system is extremely unstable, the charge/discharge control of battery in solar power system is more complicated than the charge/discharge control of ordinary battery. A complete and correct control circuit should have the following functions: prevention of back-charging, prevention of battery overcharge/discharge, temperature compensation of lead-acid battery, etc. The successful design of the charging/discharging control circuit of the spectrum solar street light will determine the success of the product.
For solar street lights, if Ni-Cd batteries are used, the battery over-discharge prevention function can be dispensed with, and if the solar panel power is not large compared to the battery, the over-charging prevention function can also be disregarded. This is the reason why many solar street lights are currently using Ni-Cd batteries. But if you use other batteries to consider the above features.
1, to prevent back-charging function, generally speaking, is to connect a diode in series in the solar cell circuit, the diode to prevent back-charging.
2, to prevent overcharging function, you can connect a drain transistor in series or parallel in the input circuit, the voltage discriminating circuit controls the switch of the transistor to drain the excess solar cell energy through the transistor to ensure that there is no excessive voltage to charge the battery.
3, in addition to Ni-Cd batteries, other batteries generally need to have a function to prevent battery over-discharge, because battery over-discharge will cause permanent damage, it should be noted that the solar panel is generally small relative to the battery discharge rate, so the discharge cut-off voltage should not be too low;.
4, temperature compensation, the above description of the battery voltage control point is changing with the ambient temperature, so the solar street lighting system should have a temperature-controlled reference voltage, thereby extending the service life of the equipment.
