# Debating the jump starting procedure



## Oso954 (Jun 23, 2012)

> I began thinking that it would be a BETTER idea to reverse the process and actually END with the last clamp going on the DONOR battery negative terminal because it is less likely that a 'good' battery on the donor car is leaking hydrogen gas.


Wrong !
The Donor battery is more likely to be producing the hydrogen gas. It is probably charging (Just started).

That doesn't mean that the "dead" battery is safe and there isn't H2 gas around it.

Go to a metal part on the dead car. Wiggle the clamp a bit, it will chew a little paint off and make contact. 

If you really want to go to the negative terminal of the dead battery, you can use a jump pack, or buy jumper cables with a safety switch.


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## Bondo (Dec 8, 2007)

Ayuh,.... I do jump starts on cars, trucks, boats, 'n heavy equipment, both 12v, 'n 12v to 24v,...

The last terminal connected is the Neg (-) terminal on my pick up truck's battery, the donor,...

Never been a problem, in all my years,...


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## de-nagorg (Feb 23, 2014)

I too hook up the last negative connection to my donor, Have a dedicated unpainted bolt just for the connection. 

Installed the connection point intentionally near the battery on my F250. 

And insist that I do the hookup, I once had a numb nuts hook it up backward, needed a new alternator after that, as well as a partially melted positive battery cable. 


ED


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## Jrannis (Nov 12, 2014)

I suspect that the advice assumes that the dead battery has a problem.
If the problem is low water (electrolyte), then gas will have a pocket to be compressed.
I would mitigate the risk of exposing a spark to explosive gasses by connecting the last lead to a remote unpainted metallic part of the donor car.


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## cjm94 (Sep 25, 2011)

Hook up negative last on what ever one you want to avoid voltage spikes to electronics. Unless you are smelling fumes coming from the battery, you are more likely to be abducted by aliens than cause a battery to explode.


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## 1985gt (Jan 8, 2011)

It can also be connected to a engine accessory mount, like alt, a/c compressor ect. Like on the 99 on chevy trucks they are connected to a grounding lug on the engine and the positive is hooked to a special connection area. 

Sometimes it's just easier to hook it to the battery.


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## rusty baker (Feb 13, 2009)

I have done battery to battery for 50 years. Never had a problem.


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## ron45 (Feb 25, 2014)

Maybe the batteries that exploded where located in the car and not under the hood.?
You could take something and fan the battery before the hook up.?


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## Bigplanz (Apr 10, 2009)

I got tired of having cables but never finding anybody around to give me a jump, so I bought a cheap harbor freight jump starter box. It really is a booster rather than jump starter. Hook it up, turn the switch to on and let it charge for five minutes. So far, so good. Started a Subaru and my villager just in the last month.


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## flhtcu (Oct 12, 2014)

rusty baker said:


> I have done battery to battery for 50 years. Never had a problem.


 So have I! Well,45 years anyway. The only one I ever saw explode was inside a body shop,when a guy put the cables of a charger on backward to the battery,made a hell of a spark,and exploded. Any time you're outside,I think any slight breeze will carry away fumes coming up from the battery.
When I was in the wrecker business and doing jump starts by the dozens on some days,I worried a lot more about getting hit by a car or a hood falling on my head.


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## iamrfixit (Jan 30, 2011)

That's the method I use, hook up both to the dead battery, then the positive to the good battery, then the negative. I will connect the negative clamp to the alternator mount or other clean metal part on the engine if one is available, but often that is not feasible so in those cases I connect directly to the negative post.

I have had two batteries blow up on me, but never when connecting or disconnecting the jumper cables. I assume both were due to some kind of internal short in the batteries. On both occasions the explosions occurred during engine cranking. 

The first time was on a car, I'd had jumper cables on it charging for a few minutes; when I tried to crank the engine the battery just blew. The second time was on a bobcat skid steer. It had previously been on a battery charger but that had been disconnected for some time and I didn't have jumper cables on it. The machine had an electronic keypad instead of a key. It would power on and allow me to enter the unlock code but then everything went blank as soon as I hit the start button. I was trying to diagnose whether there was a problem in the starter or start circuit; so I was attempting to crank the engine directly using a remote starter button attached to the solenoid. It turned over about once then boom! Turned out the battery was the problem, installed a new battery and it started up every time.

This is not something you want to experience. It is incredibly loud, like a shotgun going off too close and left my ears ringing for an hour afterward. The broken battery parts fly out of the vehicle with incredible force. Both times the only part of the battery that remained was the bottom of the case because it was clamped to the battery tray, everything else was scattered all around the site. The vaporized acid is not something you can escape, it covers the entire area and leaves your skin, eyes, nose and throat burning and leaves a horrible odor and taste hanging in the air.


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## Bob Sanders (Nov 10, 2013)

iamrfixit said:


> I have had two batteries blow up on me, but never when connecting or disconnecting the jumper cables.


Yup. Same as you. I had one blow up on me. Wasn't charging or connecting. I was just placing it in the back of a boat and for no apparent reason it blew.

I have absolutely no idea why. I wasn't handling it roughly. Nothing touched the terminals... etc. It had come off the charger maybe about an hour before and I was placing it in the battery box in the back of the boat, and BAM... 1/2 the top blew off of it and I got battery acid all over my hands and forearms.

It gave me a new respect for batteries.


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## de-nagorg (Feb 23, 2014)

I will add my theory to the reason the batteries exploding in the two previous posts occurred.

The lead/acid battery of which we speak are made with two different types of lead plates inside. And after a few years of aging one or more plates will separate from it's position, due to rough handling, or just aging. 

And the sulfuric acid will evaporate and leave small air pockets inside, and will fill with the hydrogen gasses. Especially after being charged. And when the plates fall just right they cause the ignition spark needed to blow the whole damned thing to hades. 


ED


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## ddawg16 (Aug 15, 2011)

I would like to see the scientific reasoning behind hooking up the ground last.


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## beenthere (Oct 11, 2008)

The explosion/fire risk is not from connecting to the battery. But from disconnecting. The charging of a battery is what causes the fumes/vapor.


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## polarzak (Dec 1, 2008)

I just buy a new battery.


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