Battery Terminal And Clamp

The positive post is slightly larger than the negative post so cables are hard to swap, and it is often covered by a red cap. Many modern cars have a battery sensor on the negative clamp and a pyrotechnic disconnect on the positive cable that cuts power in a crash. Clamps must be tight and clean, because a large starting current flows through a small contact area.

The clamp squeezes the lead post, giving a low-resistance path for current to and from the battery.

Loose or corroded clamps cause slow cranking, flickering lights, charging faults and random warning messages. White or green powder on the terminals is corrosion; clean it with a brush and protect the post with terminal grease.