Reverse polarity protection for Li-Ion charger
Main project requirements:
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Most Li-Ion battery charger modules lack protection against reverse polarity when connecting the battery wrongly, and the module chip burns up when connected in this way.
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It is necessary to create a protection board for a charger based on an integrated module of six TP4056.
Schematic of the device and finished device.
How it works and components used in the project.
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This circuit has been designed to protect an integrated lithium battery charger module based on six TP4056-based chargers combined into one compact module. Accordingly, 6 protection modules were made for each charger output.
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In the operating mode with the correct polarity of the connected battery, the circuit is closed, PNP transistor BC557B passes current and switches on mosfet IRF3205, the battery (on the right side of the diagram) is charged from the charger (on the left side of the diagram).
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The N-channel IRF3205 mosfet was chosen because of its low turn-on voltage threshold Vgs(ths) = 2-4V and low resistance value Rds(on)=8mOhm, to reduce the loss of current flowing through it.
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Diode 1n4007 is installed to reduce the voltage at the base of the PNP transistor to prevent base breakdown.
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In case of the connected battery will be connected in reverse polarity, the circuit with the charging module is disconnected, and the signal LED is powered.
You can find a list of used components in this project with references in the Google-document ("6xTP4056 reverse polarity protection" sheet).