Disconnecting batteries

[Kora]

What difference does it make?

When you are working on any electronics, the manual recommends to disconnect negative(-) battery terminal before you do anything. Can I disconnect positive(+) terminal instead? Is there any difference?

 

[86humv]

Safer to do negative first

 

[NDT]

If you accidentally touch your wrench to the chassis or hold down bracket when disconnecting the negative post, no big deal. Do that while disconnecting the positive post, you will not forget that anytime soon.

 

[Flyingvan911]

Negative first is better.

 

[Retiredwarhorses]

You don't want to end up being the ground!

 

[juanprado]

In another lifetime, I was a manger for Western Auto among others.

They had a real cool safety video for battery installers. 2 actual scenes were real life documentation of wearing a ring on a finger while changing a battery. The end result was not pretty and a lifelong lesson never forgotten. Actors demo the scene then they showed the real life person and very close graphic photos of the injury. Another scene was a dropped wrench in the wrong place causing a battery to go Kaboom. Not pretty.

Heck here in 100% humidity with 100* temps, I have sweated and and made electrical contacts with just sweat......

 

[Hard Head]

Fortunately for me in days gone by I wrote battery changing procedures for the govt. You disconnect neg first connect neg last. Very simple! We had a employee loose an eye due to a lead acid battery exploding when he shorted the positive to the vehicle frame with a half inch socket wrench. Don't dismiss the danger of a massive current rush. Another thing I see a lot of is non fuse protected battery circuits in military trucks. Use fuses directly at the battery to protect you, the battery, and your wire!