Why is it important to connect negative terminal away from car battery when charging?

I have read on a website that when charging your car battery, whether inside or outside of the car, you should connect the negative (black) clip away from the battery by using a jumper cable when the battery is not connected to the car or by connecting the negative clip to a piece of solid steel connected to the frame if the battery is indeed connected to the car.



Why is this?Why is it important to connect negative terminal away from car battery when charging?
The idea is that the last connection you make should be away from the battery because that's the one that will spark, and there could possibly be some hydrogen gas near the battery that could cause an explosion.

The main thing that the "experts" get wrong when you're jump starting is where to connect it. You shouldn't connect it to the frame or chassis, because you'd be pulling several hundred amps of starting current through the engine/chassis ground connection, which isn't made to handle it. You should always make that last connection to the engine block. It doesn't matter much when just charging.
Batteries give off hydrogen gas which is explosive. A spark, when connecting can set it off. That's why you should not work on a battery in an enclosed area. So long as it's in an open, well ventilated area it's not a real problem. Typically, a good battery shop would have a vent hood above the area where they service batteries. Fumes can build up under the car's hood so that's why they advise to connect the ground to the frame at a point away from the battery. The likely hood of an explosion is small but, if it occurs the explosion can smother you with flames and acid.

ADDED: Connecting to the engine block is not essential and still leaves the possibility of a spark setting off an explosion from gases that have gathered under the hood. Most batteries are grounded to the frame and the engine block has a separate ground connection to the frame. The engine ground wire is generally of small gauge and not meant to carry that much current. Connecting to the frame is much better.Why is it important to connect negative terminal away from car battery when charging?
While a battery is charging, a by-product of the electro-chemical process is hydrogen gas. Hydrogen gas is very explosive. So when connecting a jumper cable to a car battery, you first connect your positive wire to the positive battery post. Then connect the negative to anywhere on the car, since the car itself is negative ground. this method will help to avoid an unintended spark too close to the battery that may occur when you connect the second lead and possibly avoid an explosion. A spark too close to the battery may ignite residual hydrogen gas which may be present and ....Ka-boom!
To avoid sparks near the battery. Sulfuric Acid Gas is explosive. Although rare on

average, batteries have exploded because of the gas being ignited by a spark.



Charging batteries or Hot Batteries usually have a higher concentration of this gas. So

it's important to follow safety procedures to avoid such accidental combustion.



Hope this helpsWhy is it important to connect negative terminal away from car battery when charging?
The gases produced in a car battery are highly flammable. It's a safety precaution because there is usually a spark when the cables are connected.



If ignited, the battery may explode and could blow your head clean off. Do you feel lucky? ;-)
To avoid the sparks, carbonic acid is flammable and explosive.

Hook up the pos+ to the batt terminal.

the spark will fly when the circuit is complete so you move away from the batt to a grounded place not on the batt.