How to repair the 18650 li-ion battery protection board?

　　1. No voltage or abnormal voltage

　　If there is no voltage or abnormal voltage, we should adjust the multimeter to DC 20 volts, then use the red meter pen to touch the positive electrode of the 18650 li-ion battery cell, and the black meter pen to touch the negative electrode of the battery cell. If the multimeter shows no voltage or the voltage is very low , it proves that the battery core is damaged.

　　2. No overcurrent protection

　　If there is no over-current protection, etc., first check whether the circuit of the over-current detection pin is defective. If so, replace the protection IC.

　　3. No resistance or excessive resistance

　　You need to find the cause from the identification circuit of the resistor pad, check whether the identification resistor is desoldered, whether the wrong resistor is pasted, whether there is a short circuit or open circuit, etc.

　　4. There is no internal resistance or the internal resistance is too large

　　1. If there is no internal resistance, you need to check whether the pins of the mos tube are damaged. If so, just replace the mos tube.

　　2. If the internal resistance is too large, use a probe to contact the electric fish 18650 li-ion battery protection board to detect whether there is poor contact or excessive oxidation. You also need to check whether there are too many nickel flakes on the battery core. If there are too many nickel flakes on the battery core, it will also cause excessive internal resistance.

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