Battery Charger question

[Lainey]

In the Owner's Manual that came with my battery charger it says that when charging a battery that is not installed to:
"Attach at least a 24", 6ga (AWG) insulated battery cable to the Neg. battery post, connect the charger to the Pos. post, then connect the charger to the clamp of the free end of the cable attached to the Neg. post."

I'm curious why the need for the additional length of cable on the Neg. post? Thanks

[John and Nancy Hamilton]

The added length for the Negative (-) terminal is to move the connection away from the battery top where explosive hydrogen gas might be present. A spark when connecting the charger could cause and explosion.

This is why it is recommended to connect a jumper cable negative wire to the engine block, not directly to the battery terminal.

With my Schumacher battery charger, the approved method is to connect / disconnect the battery leads only when the charger is disconnect (unplugged) . This seems simpler that having an extra wire connected to the battery.

[Lainey]

thanks for the reply. Makes sense. These instructions have a person go through the connections listed in my first post also before plugging the charger in, must just be tthe manufacturer being extra cautious?

[Pete Dumbleton]

Absolutely! If you make the connections and then plug the charger in, there is no spark, but the reverse creates a spark (and may play havoc with a charger's tiny computer brain). Disconnect only after unplugging the charger.

The engine block connection advice is primarily intended for the situation where one is jump-starting one vehicle from another. Typically, the second vehicle is driven to the first and not shut down, so there is a spark (and there would likely be one even if just from the second battery).

When working with batteries, one should always presume that there will be an acid explosion (even gel cells and AGMs can fling bad stuf into your face and eyes) and behave accordingly.