Originally Posted by kyleservicetech
That's kind of strange, especially when the Powerlab 8 is rated for between one 12 Volt battery and two 12 volt batteries in series.
Its not the voltage range, but the voltage fluctuations that are the issue. I suspect that will vary considerable depending on the vehicle and condition of the car's battery. My battery is smallish and not new. So if the car's regulator dipped rapidly, the car's battery most likely could do much to prevent the input voltage from dropping from 14v to 12v. The voltage fluctuations were enough to trigger the safety code when the car was running. As that is not my typical charging scenario, I didn't pursue it.