Ask PYS: Power

Fluctuating Amperage, on May 31, 2016 asked:

I have a video of my charger display while the engine is running. At 2000 rpm, it shows that the charging voltage is constant (4.19 for the starter battery and 14.28 for the house bank), but the amperage is fluctuating all over the place, from 9.2 to 11.8A, sometimes settling around 10.4, but then fluctuating again. I understand, from our conversation, that this is not unusual? - Tim

Battery charging is governed by voltage and not current. Chargers are meant to stabilize to a voltage and use fluctuating current to keep voltage steady. Since V = IR, you cannot have both V and I steady all the time as one affects the other.  - Jeff