# Jump-starting **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [November 3, 2005, 12:56am UTC](https://boards.straightdope.com/t/jump-starting/329213 "2005-11-03T00:56:08Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Tevildo](https://avatars.discourse-cdn.com/v4/letter/t/b9bd4f/32.png) [@Tevildo](https://boards.straightdope.com/u/Tevildo)\ **Post date:** [November 3, 2005, 12:56am UTC](https://boards.straightdope.com/t/jump-starting/329213/1 "2005-11-03T00:56:08Z")
[http://www.straightdope.com/columns/050930.html](http://www.straightdope.com/columns/050930.html) A couple of additional points I’d like to make, in addition to the one about exploding hydrogen in Cecil’s original article. NOTE - I’m assuming a negative-ground car here. First, irrespective of any hydrogen that may be around, you want to avoid shorting out the good battery. If you, in defiance of the manual, connect the positive (red) lead to the good battery before you connect it to the dead one, then the other end of the lead will cause a short if it contacts any metal part of the “source” vehicle - and, if you connect the negative lead before the positive, the “target” vehicle’s metalwork is added to this risk area. As you’re likely to be working at night, with inadequate lighting, under the hood of a vehicle you’re not familiar with, the chance of an inadvertant short is decidedly non-negligible. Ignore all the other recommendations if you like, but make the first connection to the positive side of the dead battery. Secondly, although Cecil doesn’t mention this, don’t try and start the “target” car with the engine of the “source” car running. You’re probably going to blow the alternator diodes, which will leave you with two dead cars rather than one. 🙂 ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 3, 2005, 2:42am UTC](https://boards.straightdope.com/t/jump-starting/329213/2 "2005-11-03T02:42:41Z")
Wow, a brand-new guest, and not only does he know to link to the original column, and gives a well-thought response, but he’s also a Tolkien nerd. Stick around, Prince of Cats, you’ll fit in well around here. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [November 3, 2005, 12:06pm UTC](https://boards.straightdope.com/t/jump-starting/329213/3 "2005-11-03T12:06:58Z")
> [@Tevildo](#): > > Secondly, although Cecil doesn’t mention this, don’t try and start the “target” car with the engine of the “source” car running. You’re probably going to blow the alternator diodes, which will leave you with two dead cars rather than one. 🙂 Every manual or “How-to” I’ve read on the subject disagrees with this part of your post. In general, you want the “good” battery car running so that the “good” battery isn’t at any point being depleted by the electrical system of the “bad” battery car. Perhaps you have something you can point to in the way of evidence to support your assertion that the “good” car shouldn’t be running? ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [November 3, 2005, 12:08pm UTC](https://boards.straightdope.com/t/jump-starting/329213/4 "2005-11-03T12:08:03Z")
> [@Chronos](#): > > Wow, a brand-new guest, and not only does he know to link to the original column, and gives a well-thought response, but he’s also a Tolkien nerd. Stick around, Prince of Cats, you’ll fit in well around here. ?? How did you deduce all that? 😕 ---
**Author:** ![DogMom](https://avatars.discourse-cdn.com/v4/letter/d/e9c0ed/32.png) [@DogMom](https://boards.straightdope.com/u/DogMom)\ **Post date:** [November 3, 2005, 7:45pm UTC](https://boards.straightdope.com/t/jump-starting/329213/5 "2005-11-03T19:45:01Z")
[Tevildo.](http://home7.swipnet.se/~w-70531/Tolkien/tevildo/main.htm) Not being a full-fledged Tolkien Nerd, I’m not sure exactly where he / she / it is mentioned. Perhaps Chronos or Qadgop can enlighten us further. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [November 3, 2005, 10:59pm UTC](https://boards.straightdope.com/t/jump-starting/329213/6 "2005-11-03T22:59:22Z")
> [@Tevildo](#): > > [http://www.straightdope.com/columns/050930.html](http://www.straightdope.com/columns/050930.html) > > . You’re probably going to blow the alternator diodes, which will leave you with two dead cars rather than one. 🙂 Alternators are designed so that the stator iron saturates below the current limit of the rectifier diodes. You blow the diodes by reversing the polarity, which allows the other battery to forward bias the diodes, leaving only the resistance of the cables/clamps to limit current. You have to have excellent jumper cables to even do that. I know there must be other people besides me that carry good cables, but the all of the ones I’ve run across others carrying are 10AWG at best. ---
**Author:** ![Tevildo](https://avatars.discourse-cdn.com/v4/letter/t/b9bd4f/32.png) [@Tevildo](https://boards.straightdope.com/u/Tevildo)\ **Post date:** [November 4, 2005, 1:08am UTC](https://boards.straightdope.com/t/jump-starting/329213/7 "2005-11-04T01:08:18Z")
> [@Chronos](#): > > Wow, a brand-new guest, and not only does he know to link to the original column, and gives a well-thought response, but he’s also a Tolkien nerd. Stick around, Prince of Cats, you’ll fit in well around here. - smiles \* 23 years I’ve been using “Tevildo”, and only twice have I been recognized - and the other time was on alt.fan.tolkien, which is hardly an unbiassed forum. For DogMom’s information, Tevildo appears in “The Tale Of Tinúviel” in “Lost Tales 2” - he’s the original of Sauron, of whom you may have heard. 🙂 Thanks for the kind comments, I hope I’ll be able to contribute something to this most useful of sites. I apologise for the inaccuracy in my original posting re alternator diodes - I spoke only from personal experience, trying to jump-start an ancient evil (positive-earth) Mini MK2 from a slightly less ancient and much more evil Renault 5. The alternator diodes did blow, but I seem to have committed the classic _post hoc ergo propter hoc_ fallacy. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 4, 2005, 2:59am UTC](https://boards.straightdope.com/t/jump-starting/329213/8 "2005-11-04T02:59:09Z")
> [@Tevildo](#): > > 23 years I’ve been using “Tevildo”, and only twice have I been recognized - and the other time was on alt.fan.tolkien, which is hardly an unbiassed forum. For DogMom’s information, Tevildo appears in “The Tale Of Tinúviel” in “Lost Tales 2” - he’s the original of Sauron, of whom you may have heard. 🙂 Well, Tevildo certainly preceded Sauron, and was the one who first imprisoned Beren the elf, in HOMES II, but I’m not sure I’d say it’s strictly accurate to call him the _original of Sauron_, tho I’m sure we could make a lively case for it, debating it in Cafe Society here. After all, Morgoth never needed to enchant Sauron to enhance his power and evil, as far as I can recall, as was done for Tevildo. In addition… Sorry, sorry, wrong forum, I know. I just get carried away. It’s my particular… _idiom_, you know. Welcome, **Tevildo**. Hope to see you around.