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Company Logo TE Connectivity

  • Solar Charge Controller for charging Batteries

  • Created: Jun 24, 2015

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Solar Charge Controllers are voltage and/or current regulators that protect batteries from overcharging. It automatically adjusts the voltage/current level coming from the solar panel to provide the necessary power required by the battery to be recharged. Usually 12V solar panels doesn't really give a fix 12V output. The reason is that the panel can just give an ideal power to the battery when it is cool, under perfect conditions, and full sun. Also, a fully charged 12V battery is around 12.7V, so the solar panel has to put out at least that much under worst case conditions. But the solar charge controller must also regulate the voltage coming from the panel to avoid damage to the battery.

There are two types of charge controllers most commonly used in today’s solar power systems: Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT). In this circuit, it implements the PWM type. The circuit uses a microcontroller as its brain to decide the amount of power that will be delivered to the battery. The microcontroller senses the voltage level from the solar panel and also from the battery by using its analog reader pins A0 and A1, respectively. Based on the results, the microcontroller will adjust the duty cycle of the PWM signal that it sends to the base of the P2N2222A transistor to adjust the amount of charge being delivered to the battery passing through the MOSFET IRF9540. The microcontroller here is powered by the 12V battery, but since the microcontroller operates at 5V, the circuit uses a DC-DC converter to step-down the 12V battery to 5V.

Since charging batteries requires the components to be placed outdoor, high quality cables and protective molded boots must be used to ensure that the links connecting the solar panel to the charge controller and to the battery is working properly 24/7. By using TE Connectivity 202K132-25L-0 heat shrink boots, we can protect the cables from corrosion or any elements that causes the link to fail. It can resist fluids that may come in contact to solar panel and battery terminal lugs and damage it. It can also withstand from electrical voltages up to 15MV/meter. This shrink boot is rugged and yet very light weight. Additional protection, like fuse and diodes, are also used in this circuit to avoid surge current or reverse polarity that may damage the circuit.