If it provided an accurate voltage measurement at the battery terminals, that could be useful info. For example the battery should measure about 12.5 volts first thing in the morning, before starting the car. And that measurement should go up to 14-15 volts once the engine is started, then taper off toward 13 volts as you run the engine for some length of time. You could also get an estimate on the battery health by turning on the headlights (with the engine off) and seeing how much the voltage dropped. The more it dropped, the worse the battery state. Or the same idea, but observe the battery voltage drop during cranking. So with an accurate voltage display you could potentially get a heads up the battery is about to fail, and start looking for a replacement battery. Or that the alternator is about to fail, so you’d better replace it otherwise you’d be stranded soon.
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