that's way high .. certain bikes will actually charge at higher voltage at idle. but yours is charging at too high a rate and will severely overcharge agm and LiFePO4 both. 15.9v is way too high.
what's the voltage at mid-engine rpm? 30v? if so that will severely overcharge your LiFePO4 battery and could cause internal pressure safeties on cylindrical cells to pop.
-17V running at mid throttle
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