This device applies a controlled, heavy electrical load to a battery to simulate real-world operating conditions. The load is generated by a stack of carbon discs that can be compressed or relaxed to vary the resistance, and thus the current drawn from the battery. For example, when testing a 12-volt automotive battery, the device might be adjusted to draw a current equivalent to what the starter motor would demand during engine cranking.
Assessing a battery’s health under significant load is vital for determining its ability to reliably deliver power when needed most. This method provides a more accurate indication of a battery’s condition than simply measuring its open-circuit voltage. The technology has been used for decades in automotive repair shops and other settings where battery performance is critical, offering a relatively simple and robust means of evaluating battery capacity.