"proper" use of jumper cables

[tw]

Hydrogen gas problem is but another minor reason why a spark is not desireable adjacent to a battery. (Where is hydrogen concentrated when fans and engine move so much air?) But if the battery connection is via a frame, then a possible short circuit is not really a short circuit. That wire (battery to frame) slows the battery discharge meaning that battery is either less likely to explode or that the explosion would not occur as immediately - human having time to correct his mistake.

Also connecting a black wire to chassis makes it difficult to short two batteries negative to positive - making destruction of vehicle electronics less likely due to jumper leads reversed.

Problem; cars provide no good point to clamp that ground wire. Either good clamping point does not exist or jumper wire gets tangled up with fan belts, etc.

Batteries have an interesting design. Built so that batteries tend not to explode up. Instead weaker points are on the side where an explosion is less likely to take out a human face.