Your safety comes first when working with battery chargers.
Do not touch the clamps together to see if your battery charger is working. Tapping the clamps together will cause large voltage spikes at the rectifier. While the rectifier will handle a surprising amount of over current, they do not like high reverse voltage spikes. It will also stress the transformer. On newer “smart” chargers you run the risk of damaging the rectifier/SCR board/processor board depending on how it is built.
When boosting a vehicle, always check the owners manual for the battery chargers “duty cycle”. (Basically a measure of on time versus off time). A good rule of thumb is for every 10 seconds of cranking, allow 10 minutes of cool down. If you exceed the duty cycle you run the risk of tripping the thermal breaker in the charger, tripping the AC circuit breaker that the charger is plugged into, and possibly causing damage to the charger in both old transformer type and newer electronically controlled battery chargers.
Any charger plugged into a 120 VAC outlet is NOT capable of boosting on the 24-volt setting. The maximum current available from an AC outlet is typically 15 amps. For 24 VDC output, the maximum current available from the charger will be approximately 75 amps before the AC circuit breaker trips, much higher currents are available for very short periods allowing a charger to provide250 amps when boosting on the 12 volt setting.
Always use caution when connecting and disconnecting battery chargers. Hydrogen gas may be present after charging or boosting a battery, a spark generated by the clamps can ignite the hydrogen.
If you are unsure if your equipment is working properly, please be safe. Bring it into Allans Automotive for us to test it with the proper diagnostic equipment.