Battery Testers are high-rate discharge testers. These testers impose a load on the battery, which is equivalent to that drawn by the starter motor from the battery, while cranking the engine.
The tester studies the drop in battery voltage & indicates the condition of the battery – if it is capable of starting the engine or not.
All the models are fitted with a high quality 3½ digit LED voltmeter, which is powered by the battery under test.