Is it safe to connect battery charger leads to the battery while the charger is turned on?

Connecting battery charger leads to a battery while the charger is turned on is not advised because it can pose several safety risks. The high voltage produced by the charger can create a spark when the leads make contact with the battery terminals. This can be dangerous, especially in the presence of hydrogen gas which is emitted by batteries, as it is highly flammable.

Additionally, if the charger is set to a higher voltage or incorrect settings, it can potentially lead to overcharging or cause damage to the battery, impacting its capacity and lifespan. Thus, always ensuring that the charger is turned off before connecting leads eliminates these risks and promotes safer handling of the battery charging process.

Many battery chargers are designed with safety features that prevent mishaps, but the safest practice remains to always connect the charger with the power off, making this approach the most prudent in any scenario.