Modifying a knock-off battery charger to be safer

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Sometimes buying a low-cost clone off of eBay is a great option, but [Martin] wisely decided to test his counterfeit IMAX B6AC, and found it grossly lacking. His detailed breakdown shows an alarming array of problems, including poor design and construction, and a lack of warning if the balance circuit fails. In addition, the charger wasn’t properly calibrated. By using a precision multimeter, Martin found that the charger actually brought cells above critical voltage. So really, using a charger like this out of the box can both destroy your battery pack and/or start a fire. One other interesting detail – this model can only be calibrated once. Sweet features.

[Martin] detailed his fixes in a well-illustrated blog post. He first had to re-enable the calibration menu using this method which requires bricking the device first! Once un-bricked, however, he could do the recalibration using a voltage divider and a reliable power source.

This project really underscores the need for a precisely calibrated multimeter. Not only would [Martin] not have been able to test his charger properly, but the re-calibration wouldn’t have been as accurate as needed. As hobbyists, this is a reminder that we can only trust our tools if they are accurate.