A load tester is recognizable by the fact that it's a box with holes (for ventilation) about 6" X 5" X 12" long with short clamp cables and a meter.
Other units are hinged without clamps so you can spread the contacts to touch your battery's terminals. The construction uses a brush-on-coil so the amount of resistance is set by the angle of the tool.
Either holds a resistance coil of wire through which the battery's juice is sent. It will warm up hence the ventilation.
They leave it connected for 10 seconds or so to see how strong your battery is. It's been called "the only real way" to test a battery.
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