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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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  • \$\begingroup\$ Is the problem due to one component being hot and warming the others? Dig deeper. \$\endgroup\$ – Andy aka Feb 7 at 14:02
  • \$\begingroup\$ As per as my observation, during charging all the above mentioned components are heating gradually with the charging time and all are heating simultaneously. They are not heating just because of heating of one component only. \$\endgroup\$ – Aakash Dey Feb 7 at 14:06
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    \$\begingroup\$ "heating too much" <-- too much according to what? \$\endgroup\$ – Marcus Müller Feb 7 at 14:11
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    \$\begingroup\$ @MarcusMüller Even so, I think "too hot to touch" on an electrolytic cap is a bad sign! Exactly what is "too hot to touch" varies, but I've generally seen it reported as around 50°C and above (where first-degree burns start to happen). Aluminum electrolytics generally do not like temperatures much above room temperature. \$\endgroup\$ – Hearth Feb 7 at 15:49
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    \$\begingroup\$ @Hearth fully agree! But no matter how we help Aakash, it will end up with him figuring out where the power for the temperature delta comes from. \$\endgroup\$ – Marcus Müller Feb 7 at 17:14
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C1 looks backwards on your silk screen (certainly its the other way wround from C8). Is it possible you've fitted it back to front and it's drawing current and getting hot? That current would also heat D1, and the lack of decent decoupling would then put more stress on Q1 D3,D4 and L1 making them hot.

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  • \$\begingroup\$ @james, C1 is an input bypass capacitor and on the PCB also the positive terminal of the capacitor is connected to the power supply line and negative terminal is connected to the GND plane. So, i have connected the C1 and D1 also in right and correct direction. (no possibility of backward connection). \$\endgroup\$ – Aakash Dey Feb 8 at 5:06
  • \$\begingroup\$ Oh I see it's JP1 that's backwards the + symbol on JP1 is actually the Ground connection, C1 is the right way round. \$\endgroup\$ – james Feb 10 at 1:42

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