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BQ40Z50-R1: OC Flag & Internal Charge Counter

Part Number: BQ40Z50-R1

We have built a number of battery packs with this device and 5-10% of the batch experience an OC condition when they are charged which causes the charge cycle to terminate during the CV stage.

The OC settings are set to: 

Threshold = 1100mAh,

Recovery = 1mAh

Recovery RSoC = 95%

RSOCL is cleared

I don't understand why the OC flag is being set. I'm wondering what causes the internal charge counter to reset? If I were to repeatedly charge a battery with no discharge in between, would the charge counter keep accumulating or would it start at 0 each time?

Our FCC is 1000mAh so in theory, it should never trip as it would have to overcharge by its full capacity before the counter triggered it.

It's an awkward problem to diagnose because the OC flag doesn't get logged in the lifetime data. The only suggestion that it's occurred is that the OC Safety Alert is still on (once charging stops, the OC Safety Trip clears pretty quickly)

Thanks, in advance, for your help.