WARNING!!! Automotive Battery Disconnect Switches

WARNING!!! NEVER connect your automotive battery disconnect switch to the POSITIVE terminal of your battery. This is true for ALL top-post and side-post batteries*.

Why not?
#1 - They usually won't fit.
#2 - It's not safe. All battery disconnect switches add additional, exposed area to the terminal it is connected to. Whether it be a top-post or side-post disconnect switch. This additional surface area can more easily come in contact with other metal parts within the engine compartment. These other metal parts are usually negative grounded. And if the two connect, at the very least you will see a LOT of sparks. You might burn-up your battery cable, wiring harness, incur bodily injury, or ALL of the above.

* (On negative-grounded vehicles. Most vehicles built after the mid-1950s are negative-grounded.)

[tronarat]

I was wundering about this since I putting one of these on my truck that only gets used once every few months I remember in shop class our teacher saying any car with a ecu never disconnect the positive terminal and if you do negative comes off first great video saved me a headache down the road

[TheErodChannel]

In my youth, I once got a socket wrench across the positive 6 volt battery terminal and the rear seat frame of my 1956 Volkswagen. I can absolutely verify that a socket wrench will glow very red when shorted across a 6 Volt battery. The socket wrench welded itself to the seat frame and I had to kick it loose before the battery reached critical mass.

[guykargl]

You are 100% correct about the danger of creating a short from positive battery terminal to chassis ground.  However, the safest method is to isolate the positive terminal with the battery disconnect switch, and then properly insulate the battery disconnect switch itself.

[peterport]

You should be careful with your callipers. In this video they came very close to shorting your battery. Not a good example given your warning later with the ring spanner example.

[fatsolutions]

Thank you for posting this video, hopefully this saves people from injuring themselves! I have seen some Injuries from tools arcing across terminals mostly 24vdc and multiple batteries.

[ascendedtaco]

You sir are a gentlemen and a scholar, and there are few of us left.

[MrStefGamble]

Did you see how close that guy came to melting his caliper (?) when showing the terminal diameters ?
A very dangerous demonstration as one who has seen a shorted battery explode will testify.

[zachy]

In the end of this video you complain about 'so called mechanics' leaving their tools across the battery and how its dangerous and such.   but at the 0:50 mark your dial calipers are about 1/2 away from hitting both posts

[fivefatcats]

when I was 17, while installing a battery and connecting the positive connection I accidentally hit the fender with the wrench (yes, i had connected the negative already - my bad). That sucker gave one spark and blew the lid right off the battery. It was wintertime, and i had on a hooded grey sweatshirt. I got a small cut between the eyes from flying plastic and turned the hood of the sweatshirt bleach white. I got an ambulance ride but fortunately had no acid burns to my eyes. Lesson learned. I am still appropriately overcautious around batteries now.

[MrDanielrbales]

You talk about leaving tools on the battery, what about the micrometer you used to almost connect the positive and negative?

[JerryLester]

You confirmed what I suspected since the quick disconnect was apparently too small for the positive terminal of my top terminal battery. Thanks.

[Harry-nqqf]

Definitely reshoot the micrometer scene. I thought for sure we were going to see an explosion. Other than that GREAT INFORMATIVE VIDEO!

[lostintime]

Are you "positive" about this??

[danmatthews]

Thanks for posting this. Caliper end was dangerously close. No mention that batteries can go BOOM from the explosive gasses?

[Screwdriversteve]

Wow you almost shorted the battery with your caliper and you are wearing a ring!!! woops!

[thespyderryder]

Finally someone posts a very useful warning! Good job!

[rogerthomas]

thank you never done this and had no details of how to so thank you very much for your info. now i can go forge ahead

[atan]

By installing battery kill switch, will it affect the engine management system?

[enriquejaramillo]

You are the MAN. hopefully all those "mechanics" are watching your videos thanks for your video.

[captainspire]

I have an old Chevy Astro 89 I want to install a battery cut off switch to. I don't want a Frankenstein's power level and I dont want to have to open my hood to turn and twist a knob every time I'm ready to leave. I want to know if I can install an on and off switch, to the battery that mounts inside the car, I can flip to get the battery to make contact. There is some parasitic voltage leak that kills the battery within 1-2 weeks of non use and I cannot find where it's drawing from.