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Solar battery charger

Efficient charging in all lighting conditions

Using a solar cell to charge a battery is a very popular application. However, solar cells also present challenges because of the wide variability of the output voltage, depending on the amount of solar energy directed at the panel, temperature, and the load on the panel. Utilizing the benefits of the ISL81601 buck-boost controller, this design can be used to charge a wide array of battery voltages even if the solar panel is delivering an output voltage much lower than its nominal output. An RL78/G14 MCU is added to ensure that the battery is not overcharged and to monitor the status of the battery. With the addition of MPPT firmware, the RL78/G14 can control the ISL81601 to maximize the efficiency of the solar panels. Depending on the voltage of the solar array used, an optional DC/DC has been added to increase efficiency in higher voltage applications.

Key features

  • Buck-boost architecture charges the battery even when the voltage of the solar panel is below the battery voltage
  • Programmable charge rates to support various modes, such as fast-charge and trickle-charge
  • Up to 60V input and adjustable output voltage of 0.8V to 60V
  • Monitors battery status and protects battery from damage caused by over-charging
walkway lined with solar yard lights

Recommended products

Products Description Documents
RL78/G14 Low power consumption, high function general-purpose microcontrollers User's manual
Buck-Boost Controller    
ISL81601 60V bidirectional 4-switch synchronous buck-boost controller Datasheet
Switching Regulator    
ISL8117 Synchronous step-down PWM controllers Datasheet


Block diagram

block diagram

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