# Jumper Cables **URL:** \ **Category:** Factual Questions\ **Created:** [May 30, 2004, 11:49pm UTC](https://boards.straightdope.com/t/jumper-cables/247858 "2004-05-30T23:49:40Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![silenus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/silenus/32/166_2.png) [@silenus](https://boards.straightdope.com/u/silenus)\ **Post date:** [May 31, 2004, 4:55am UTC](https://boards.straightdope.com/t/jumper-cables/247858/21 "2004-05-31T04:55:04Z")
> [@Reeder](#): > > You know…I remember a time when you only needed one cable to jump start. > > You hooked positive to positive and touched the bumpers together. > > Boy am I old. Wow. I thought I was the only one who learned how to do it that way! Old drivers of old cars…unite!!! 😃 **Reeder,** do you remember when you could open the hood and point to and name everything under there? ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [May 31, 2004, 5:04am UTC](https://boards.straightdope.com/t/jumper-cables/247858/22 "2004-05-31T05:04:33Z")
Now I remember why I no longer offer anyone a jump. Not even to a pretty girl. “I’ can do it” Famous last words. So why is my little idiot light suddenly lit? $120.00 learning experience. Twice. Fool me once, etc. Peace, mangeorge ---
**Author:** ![lektrikpuke](https://avatars.discourse-cdn.com/v4/letter/l/47e85d/32.png) [@lektrikpuke](https://boards.straightdope.com/u/lektrikpuke)\ **Post date:** [May 31, 2004, 7:09am UTC](https://boards.straightdope.com/t/jumper-cables/247858/23 "2004-05-31T07:09:10Z")
All wet lead acid batteries (and other battery topologies as well) vent gases. Sealed, maintenance free batteries still have pressure relief valves that can vent gases. Always avoid sparks around batteries however you choose to do it. I once had a motorcycle battery explode while trying to bump start it. Nearly blew the seat off the bike while I was sitting on it (and I’m over 200 lbs). ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [May 31, 2004, 7:23am UTC](https://boards.straightdope.com/t/jumper-cables/247858/24 "2004-05-31T07:23:50Z")
> [@Balthisar](#): > > My previous car never had the occassion to jump or be jumped – but there was no battery under the hood, so I guess it was a moo\* point. It’s like a cow’s opinion, it doesn’t matter! ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [May 31, 2004, 8:57pm UTC](https://boards.straightdope.com/t/jumper-cables/247858/25 "2004-05-31T20:57:55Z")
> [@Balthisar](#): > > Of course maintenance free batteries are sealed units, and don’t give off gasses, right? – that’s a question, because the answer helps or hinders what I’m going to say next: wouldn’t that obviate the need to remember to hook to a ground rather than the negative terminal on the dead car? > > My previous car never had the occassion to jump or be jumped – but there was no battery under the hood, so I guess it was a moo\* point. > > \*not a typo; just a _Friends_ ripoff. I drove an old VW Bug around for months sans battery. No problem, just try to park on a hill. Even failing that, make sure you have room to push it out. Push, push, push, then jump in and drop it into 2nd. Life used to be so simple. It wasn’t really, but It’s nice to remember it that way. 😉 ---
**Author:** ![Reeder](https://avatars.discourse-cdn.com/v4/letter/r/c6cbf5/32.png) [@Reeder](https://boards.straightdope.com/u/Reeder)\ **Post date:** [May 31, 2004, 10:12pm UTC](https://boards.straightdope.com/t/jumper-cables/247858/26 "2004-05-31T22:12:18Z")
> [@silenus](#): > > Wow. I thought I was the only one who learned how to do it that way! > > Old drivers of old cars…unite!!! 😃 > > **Reeder,** do you remember when you could open the hood and point to and name everything under there? Oh yes. I remember the days when you could work on your car yourself. Now you just about need a degree in automotive science to do it. Plus equipment the common man could never afford. i have great memories of rebuilding the old dodge slant 6’s. IMHO the best motor ever built. And all you needed was hand tools. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [May 31, 2004, 11:53pm UTC](https://boards.straightdope.com/t/jumper-cables/247858/27 "2004-05-31T23:53:31Z")
> [@Reeder](#): > > Oh yes. I remember the days when you could work on your car yourself. Now you just about need a degree in automotive science to do it. Plus equipment the common man could never afford. > > i have great memories of rebuilding the old dodge slant 6’s. IMHO the best motor ever built. And all you needed was hand tools. Except that you could hardly work on it outside the car w/o an engine stand. Well, you could but you had to make do. We put 4x4’s (wood, not Jeeps) under the “slant” side. The old 290 cid (is that right?) “truck” 6 had to be a close 2nd. ---
**Author:** ![Reeder](https://avatars.discourse-cdn.com/v4/letter/r/c6cbf5/32.png) [@Reeder](https://boards.straightdope.com/u/Reeder)\ **Post date:** [June 1, 2004, 12:18am UTC](https://boards.straightdope.com/t/jumper-cables/247858/28 "2004-06-01T00:18:13Z")
> [@mangeorge](#): > > Except that you could hardly work on it outside the car w/o an engine stand. Well, you could but you had to make do. We put 4x4’s (wood, not Jeeps) under the “slant” side. > The old 290 cid (is that right?) “truck” 6 had to be a close 2nd. We didn’t pull the motor other than to pull the head. We did it still in the car. Just drop the crossmember and go at it. Two guys could do it in two days. Things were so much simpler. We did have to send the head out to get it done. We didn’t have that skill. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [June 1, 2004, 12:42am UTC](https://boards.straightdope.com/t/jumper-cables/247858/29 "2004-06-01T00:42:15Z")
> [@Reeder](#): > > We didn’t pull the motor other than to pull the head. We did it still in the car. Just drop the crossmember and go at it. Two guys could do it in two days. Things were so much simpler. We did have to send the head out to get it done. We didn’t have that skill. No, normally you wouldn’t. But we were limping along on a hosed engine in the car (a Valiant) while we worked over the “new” one. Bore + stroke + carbs + cam + split exhaust = a pretty torquey little six banger. Surprised the hell outta a lot of small block chevvies. 😉 Sounded bad too, like an Indy car. Remember cut-outs, on the exhaust pipes? Four little bolts and you were _FREE_. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [June 1, 2004, 3:00am UTC](https://boards.straightdope.com/t/jumper-cables/247858/30 "2004-06-01T03:00:02Z")
Per the label on my booster cables (emphasis mine): > [@](#): > > 1. Make sure the two cars are not touching and the ignition switches are off. > > 2. Connect one clamp to the ‘dead’ battery terminal wired to starter or solenoid (Positive (+) Post.) **[i.e., connect the red clamp to the positive terminal of the car being started]** > > 3. Connect the other end of the cable with the same color coded clamp to the Positive (+) post of the good battery. **[i.e., attach the other red clamp to the positive terminal of the donor car.]** > > 4. Connect the other **[black]** clamp to the **Negative (-) post** of the ‘good’ battery. > > 5. Connect the remaining **black** clamp to the engine block of the stalled car as far away from the battery as possible. > > 6. Start car and immediately remove clamps, reversing the procedure by removing the clamp at the engine block first. So: Red clamps to the **terminals** of the batteries. Black clamps to the **negative terminal** of the donor car, and to the engine block or other grounded bit on the stalled car. (And yes, I know – and it’s been posted – that the batteries don’t care what colour goes where, as long as they connections are correct. But “red to positive, black to negative” is the convention, and if adhered to can prevent accidents.) ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [June 1, 2004, 2:00pm UTC](https://boards.straightdope.com/t/jumper-cables/247858/31 "2004-06-01T14:00:17Z")
Since no one’s stated it explicitly, though the data is there if you read all the posts - the reason the final connection is to bare metal and not to the battery is to prevent an explosion. Car batteries produce hydrogen gas, which can be explosive in high enough concentrations. The final connection of the jumper cables can (and IME usually does) produce sparks. Keeping the sparks away from the gas-producing battery is a good thing. The odds of explosion are pretty low even if you do make the final connection on the battery though, as **Lambo’s** continued existence demonstrates. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 1, 2004, 3:48pm UTC](https://boards.straightdope.com/t/jumper-cables/247858/32 "2004-06-01T15:48:48Z")
I don’t know if anyone else here has ever seen a battey explode, but it is fairly impressive. The one I saw blow sent a piece of the top of the battery about 25 feet into the air and gave the guy near it a fairly good shower of battery acid. Enough to convince me not to make that last connection to the battery… ---
**Author:** ![spinky](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@spinky](https://boards.straightdope.com/u/spinky)\ **Post date:** [June 3, 2004, 8:28am UTC](https://boards.straightdope.com/t/jumper-cables/247858/33 "2004-06-03T08:28:11Z")
What I’ve always wondered is… since it’s often hard (on modern cars) to find bare metal to clamp to ( **everything** in my Honda’s engine compartment is painted), why not have a break in the middle of the negative cable, such that you can safely connect red to positive on both sides, then black to negative on both sides, then connect the break in the middle of the black cable, creating the sparks a safe distance from either battery? Really nice cables could even have a proper switch to throw. ---
**Author:** ![LouisB](https://avatars.discourse-cdn.com/v4/letter/l/dfb087/32.png) [@LouisB](https://boards.straightdope.com/u/LouisB)\ **Post date:** [June 3, 2004, 11:08am UTC](https://boards.straightdope.com/t/jumper-cables/247858/34 "2004-06-03T11:08:49Z")
> [@mangeorge](#): > > No, normally you wouldn’t. But we were limping along on a hosed engine in the car (a Valiant) while we worked over the “new” one. Bore + stroke + carbs + cam + split exhaust = a pretty torquey little six banger. Surprised the hell outta a lot of small block chevvies. 😉 Sounded bad too, like an Indy car. > Remember cut-outs, on the exhaust pipes? Four little bolts and you were _FREE_. I’m getting all nostalgic for the 50s and 60s. Overhauling VW aircooled engines was even easier. **mangeorge,** you could have wound a rope around the crankshaft pulley and started the thing like you pull start a power mower or a small outboard. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [June 3, 2004, 5:06pm UTC](https://boards.straightdope.com/t/jumper-cables/247858/35 "2004-06-03T17:06:35Z")
My friend had two (hi performance) engines for his Bug. He never worked on one in the car. When it came time for an oil change and valve adj, he’s just swap it out (under 30 min.) and put the “out” engine on a stand. Then he could do the work and any tweaking at his leisure. To tell the truth, I’ll take my A4 over any other car I’ve ever owned. I don’t really miss wrenching at all. That’s why they make mechanics, and why I’m glad can afford one. 😉 [Previous page](https://boards.straightdope.com/t/jumper-cables/247858.md?page=1)