Our test agency has informed us that our charging design fails IEC62368-1 M.4.2 "Charging safeguards for equipment containing secondary lithium battery". Our design uses the BQ24072T that connects to an IEC62133 certified battery through a third-party fuel gauge IC. The single fault that was applied which led to this failure was a short-circuit between pins 13 (VBUS) and pin 2 (BAT). According to the test agency, under any single fault condition the charger must stop charging the battery. However, according to their data the charging system continued to charge the battery.
Since the BQ24072T was bypassed, I don't see how it can be expected, on its own, to clear the fault and prevent charge current from entering the battery. Does this mean we require an additional overvoltage protection circuit between the battery and the charger IC? If so, can anyone recommend a potential solution?
With kind regards.
