One of two things are happening. If the charger is turned on before it is connected to the battery, the sparks will occur when it's connected and current starts to flow. In that situation the sparks can be expected to occur, but it is very important to avoid that. Batteries give off explosive hydrogen gas, and those sparks can cause an explosion. The charger should always be turned off when it is being connected to the battery, then again just before you disconnect the cables. Only turn it on or off after the cables have been connected to the battery.
If the charger is off when the sparks occur, the cables are connected backward. One cable will have a red boot over the clamp, or the wire will be red. That one goes to the battery's positive post. The negative cable is black or has a black boot. Standard practice is to connect that one last to a paint-free point on the engine. Any sparks are going to occur when the second cable is connected, and when the first one is disconnected. By always making that the black cable on the engine, any sparks will be some distance from the battery and that hydrogen gas.
You might find these articles do a better job of explaining this:
https://www.2carpros.com/articles/how-to-charge-your-car-battery
https://www.2carpros.com/articles/how-to-jump-start-car-battery-using-jumper-cables
https://youtu.be/6x8RpV2p2R0
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Thursday, May 20th, 2021 AT 10:30 PM
