"proper" use of jumper cables

[tw]

Originally Posted by Aston

According to most manuals, connect positive terminals first then negative terminals.The battery forms hydrogen, and that's the reason why for connecting the negative to the chassie, and not to the battery negative.

That spark exists if connecting direct to a battery or indirectly via a chassis. Hydrogen has nothing to do with it.

Positive is connected first so that either + terminal does not accidentally connect to most everything else. 'Everything else' is connected to the - terminal. Firmly attaching those red clamps before making any other connection makes an accidental short less likely.

Connecting to a chassis - not battery - is so that an accidental short circuit is less likely to cause a battery explosion. An explosion not due to ignited hydrogen. A battery that is shorted can get so internally hot as to explode.

Why do I know? We learn this stuff from experience (mistakes).