Jumping a car battery argument

[50]

So I had an argument a couple of days ago with a friend over how to jump a car. I always do the following:

1. Start the working vehicle
2. Attach Positive on working, then positive on dead, then negative on working then negative cable to chasis ground of dead.
3. Wait about a minute and start the dead vehicle up. Then disconnect cables in reverse order.

He said this will destroy the battery. His method was leave both cars off

Attach positive of working vehicle, then positive to dead vehicle. Negative of working vehicle to negative of dead vehicle. Do not start either vehicle, wait a minute, disconnect opposite order then start dead vehicle

I told him that puts both of the batteries in parallel and will cause damage to the good battery. Who's right?


Moved from the Off Topic forum over to The Garage.

Anandtech Moderator
KeithTalent

 

[BoomerD]

Neither of you is right...

http://artofmanliness.com/2008/09/11/how-to-jump-start-a-car/

http://www.cartalk.com/content/features/jumpstart/images/jumpstart.pdf

 

[Tweak155]

You're right. That dude has clearly never jump started a vehicle. Although I'm not sure what he stated would damage the batteries.

Leaving them connected would probably work (and not running) but you're draining a battery that isn't being charged, you could end up with 2 dead batteries.

 

[Atomic Playboy]

Every set of jumper cables I've ever used has pretty explicit instructions for how to do it. I don't remember them off-hand, even though I've had to jump more cars in the past 6 months than in the rest of my life combined, but I just followed the order of operations listed on the instructions, and it worked like a charm.

 

[Numenorean]

1 - Cars both off.
2 - Connect positive to dead vehicle battery post.
3 - Connect positive to live vehicle battery post.
4 - Connect negative to live vehicle battery post.
5 - Connect negative to dead vehicle, preferably to metal chassis.
6 - Start working vehicle. Let idle for a minute or two.
7 - Start the dead car.
8 - Disconnect cables in reverse order.

 

[JCH13]

You're right. That dude has clearly never jump started a vehicle. Although I'm not sure what he stated would damage the batteries.

Leaving them connected would probably work (and not running) but you're draining a battery that isn't being charged, you could end up with 2 dead batteries.

This. Connecting two batteries together and letting them equalize charge is bad news.

 

[linjy2]

1 - Cars both off.
2 - Connect positive to dead vehicle battery post.
3 - Connect positive to live vehicle battery post.
4 - Connect negative to live vehicle battery post.
5 - Connect negative to dead vehicle, preferably to metal chassis.
6 - Start working vehicle. Let idle for a minute or two.
7 - Start the dead car.
8 - Disconnect cables in reverse order.

+1

 

[vshah]

1 - Cars both off.
2 - Connect positive to dead vehicle battery post.
3 - Connect positive to live vehicle battery post.
4 - Connect negative to live vehicle battery post.
5 - Connect negative to dead vehicle, preferably to metal chassis.
6 - Start working vehicle. Let idle for a minute or two.
7 - Start the dead car.
8 - Disconnect cables in reverse order.

this is the way i've always done it as well

 

[desy]

You're not supposed to have the charge car running in case there is a mjaor electrical problem with the dead car because it will wack your alternator and charging system. That way if the dead car is that out of shape it only takes your battery with it.
Order you hook them up in is supposed to matter for sparking and battery gases

Personally I hook everything up and don't really care who gets hooked up first while the charge car is running and go ahead to try and start the dead car. In 30 yrs I've never had a problem and we boost a lot around here in -40 weather

 

[Mr. Pedantic]

Off
Positive to dead
Positive to live
Negative to live
Negative to metal part of dead's engine
Start the working car. Leave for a few minutes
Turn off the working car.
Disconnect the cables in reverse order
Turn on dead car.

 

[FuzzyDunlop]

1 - Cars both off.
2 - Connect positive to dead vehicle battery post.
3 - Connect positive to live vehicle battery post.
4 - Connect negative to live vehicle battery post.
5 - Connect negative to dead vehicle, preferably to metal chassis.
6 - Start working vehicle. Let idle for a minute or two.
7 - Start the dead car.
8 - Disconnect cables in reverse order.

This. You can even connect the cables to the working car while its running. No need to shut it off at all.
Revving up the engine on the working car will also help if its really cold out.

 

[sleep]

This. You can even connect the cables to the working car while its running. No need to shut it off at all.
Revving up the engine on the working car will also help if its really cold out.

this is how i do mine.

 

[Howard]

Does it really make a difference whether you make the first positive connection to either the dead or live car?

 

[ShawnD1]

Leaving them connected would probably work (and not running) but you're draining a battery that isn't being charged, you could end up with 2 dead batteries.

That's what my dad always said. Make damn sure your vehicle is up and running before you start screwing around. The last thing you want is to be stranded when it's -30 outside. My dad has jump started a lot of cars in his day so I'm guessing he's saying this because he actually did get stranded once.

Does it really make a difference whether you make the first positive connection to either the dead or live car?

No. Only the last connection to close the loop matters. The last connection should always be to the working battery because dead batteries can sometimes leak hydrogen gas.


So basically there's just a few things to keep in mind
1 - your car should be running before you start hooking stuff up
2 - connect the jumpers on the dead battery first
3 - give a tap test when connecting to the good battery. if there's a large spark, that's a good sign the dead battery is internally faulted and you should NOT try to boost it!
4 - if there is only a tiny spark or no spark, clamp it and start the other guy's car
5 - immediately disconnect the jumpers from the good battery

The last part is to protect your alternator. We went over this in the last thread. Alternators are not intended for charging dead batteries. Using your alternator to charge a dead battery is a great way to burn out your alternator. Let the other guy burn out his own alternator.

 

[bryanW1995]

Too bad we didn't have the interwebz back in the day... Back when I was selling used cars in Houston (1998), one of my buddies one day went out to the lot to help a customer jump start his bmw. Apparently, the early 90's bmw's +/- connections were reversed from the "normal" American batteries that he was used to and, well, um, there was a small explosion. Customer did NOT buy a car from us, and my buddy had to buy a new shirt, but fortunately he didn't get any in his eyes at least.

 

[ShawnD1]

Apparently, the early 90's bmw's +/- connections were reversed from the "normal" American batteries

LOL
Remind me never to buy a BMW. The reason American cars hook the negative terminal to the frame is because the negative terminal (cathode) resists corrosion. It's simple high school chemistry.
Doing it the other way and hooking the positive to the frame would greatly increase the speed of rusting.


In any event, the polarity thing is why you always touch the outside of the alligator clip to the battery terminal before you try clamping it on. If there's a really big spark, you know it's backwards or the battery is internally shorted. If you just went ahead and clamped it on before checking, it might blow up before you have a chance to unclamp it.

 

[Eli]

A battery that is being used or charged produces hydrogen gas. They're not producing anything if they're not powering a load or being charged, especially if it's dead...lol

Every instruction I've ever read, you complete the circuit at the dead battery.

And positive and negative are usually clearly marked with the cables, if not then on the battery. All American cars most certainly do not use the same orientation for positive and negative. The guy was just an idiot.

 

[Throckmorton]

I've always wondered... What is the reason for connecting to the frame instead of the - post?

 

[reallyscrued]

LOL
Remind me never to buy a BMW. The reason American cars hook the negative terminal to the frame is because the negative terminal (cathode) resists corrosion. It's simple high school chemistry.
Doing it the other way and hooking the positive to the frame would greatly increase the speed of rusting.

I'm pretty sure he meant that the wrong colored cables were used for neg/positive and that was the source of confusion, not that positive was hooked to the frame.

Btw, never buy a BMW. Not because they are bad cars...just...you shouldn't drive one.

 

[LTC8K6]

Yeah, a 90's BMW would not use a positive ground system.

 

[herm0016]

actually some cars used to have positive grounds for some reason, i don't remember why exactly.

what is the reason for positive first, I have always grounded things first when working with electronics, though its not really the same thing i guess.

 

[5150MyU]

I've always wondered... What is the reason for connecting to the frame instead of the - post?

Spark explosion

 

[BUTCH1]

I won't jump anyone, a battery can have some charge on it but not enough to start the car OR be so dead it won't even light a bulb, in the second case your putting an extreme load on YOUR alternator and risking toasting it, fuck that..

 

[Vasp]

Michelin Smart Jumper cables for easier jump-starts

http://reviews.cnet.com/8301-13746_7-20063320-48.html

 

[Meghan54]

I won't jump anyone, a battery can have some charge on it but not enough to start the car OR be so dead it won't even light a bulb, in the second case your putting an extreme load on YOUR alternator and risking toasting it, fuck that..

Highly doubtful that that would happen.....the battery's what's giving the jump, not your alternator, at least directly. So the load's being taken, initially, by your battery. And a short duration of pull off your elect. system shouldn't toast anything on your car, unless your vehicle's elect. system is in bad shape to begin with.