voltage across battery when charging ?

[Gearhead999]

To load test the battery. The car is off. The tester is hooked up to battery. The test puts an adjustable load on the battery so you can see what kind of reserve power it has with the load.

To test the charging system under load. You start the car and then load it up.

On a Load test for starter/charging system/batteries, you take the load probe [it's a clamp that you put around the wire to read amps] and put it on the bat. wire at the alternator, while the car is running. This will tell you what kind of amps the alternator is putting out, at the alternator before it gets to the car and battery.