Heating issues with solar charging circuit

Thread Starter

aakash dey

Joined Feb 7, 2019
5
I am using the above circuit to charge a 7.4V Li-ion Battery.With input MPPT voltage set at 12V, I have applied 13V input voltage to the circuit. The battery is charging at 1.4A. (according to the calculation it should be 2A). But, the input diode D1, Input capacitor C1, MOSFET Q1, diodes D3 and D4, Inductor L1 are heating too much during charging. What could be the reason of heating ? Any design problem or other?
 

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wayneh

Joined Sep 9, 2010
17,031
I am using the above circuit to charge a 7.4V Li-ion Battery.With input MPPT voltage set at 12V, I have applied 13V input voltage to the circuit. The battery is charging at 1.4A. (according to the calculation it should be 2A). But, the input diode D1, Input capacitor C1, MOSFET Q1, diodes D3 and D4, Inductor L1 are heating too much during charging. What could be the reason of heating ? Any design problem or other?
Could the heating be coming from outside the circuit, eg. the enclosure sitting in the sun? It sounds to me like generalized heating that may not be circuit-related. C1 really should not be getting warm unless a large AC component is coming in from the solar panel. Is the panel ground and circuit ground properly connected?
 

Thread Starter

aakash dey

Joined Feb 7, 2019
5
No. the heating is on the circuit itself. Because I have checked the circuit behavior by applying power supply through an voltage variable SMPS. In this case also, Input diode and input capacitor are also heating. MOsFET, the 2 pass diodes and inductor are also overheating.

The power supply GND and circuit GND are well connected.
 

Thread Starter

aakash dey

Joined Feb 7, 2019
5
Ya. I have replaced the input capacitor by a larger value (47uF) and found that the input capacitor and the input diode not heating now. I was guessing that input power supply trace is not sufficient. Now, problem is that MosFET, diode D3 and D4 are still heating. Is it a routing problem?
 

wayneh

Joined Sep 9, 2010
17,031
Ya. I have replaced the input capacitor by a larger value (47uF) and found that the input capacitor and the input diode not heating now. I was guessing that input power supply trace is not sufficient. Now, problem is that MosFET, diode D3 and D4 are still heating. Is it a routing problem?
It's not possible to diagnose build issues without seeing your build! It would be a good idea to follow the high-current path and take as much of it as possible off the PCB. Use wire to parallel whatever traces are critical and don't forget the ground return path.
 
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