REVscene - Vancouver Automotive Forum

thumper · 12-20-2008, 11:52 AM

which is the correct way to hook up jumper cables to a dead battery in a car? ie. does the negative clamp go to the negative terminal, or does it go to ground somewhere on the engine?

i always thought it was option no. 2, but my friend jumpstarted his car with it hooked to the neg. terminal just now and i'm confused

Presto · 12-20-2008, 12:07 PM

The way I learned to do it was connect the the + - terminals on the good car, and on the car that needs jumping, connect to the appropriate + terminal , and connect the ground cable to the chassis.

EuroTRASH · 12-20-2008, 12:20 PM

i always just go battery to battery

the idea behind going to a ground elsewhere, is that if there's hydrogen buildup surrounding the battery, the spark from connecting the cable can ignite it, which is possible.

Another very important safety tip, is to hook up one wire at a time

do both +, then both -

never do + and - on one car first, because then the other ends of the cables are "live" meaning that if you touch them together, or touch them both to the same thing, you'll make a short circuit, damaging something, or if you grab both ends, you'll hurt yourself.

thumper · 12-20-2008, 12:58 PM

should the car that is jumping be running while the cables are being hooked up? again, i thought the engine had to be shut off to minimize any potential accidents, but he did it with the car running...

jack_dangerous · 12-20-2008, 02:16 PM

Quote:

Originally Posted by thumper

should the car that is jumping be running while the cables are being hooked up? again, i thought the engine had to be shut off to minimize any potential accidents, but he did it with the car running...

well you can do it either way.. but with the engine running you have more danger of possibly catching something in the fan belt or something...

underscore · 12-20-2008, 03:27 PM

first you connect both - clamps, on the dead car it should be connected to a good chassis ground and not the battery. connect the + on the rescuing car to the battery, and start it. now take the remaining + and connect it to the battery, right as you do this start up the dead car. once it's running remove the + and the rest of the wires in the opposite order of install.

reasonings:
1) a running car can provide more current and more voltage than a battery alone
2) use the chassis to prevent explosions from the combonation of hydrogen gas + a spark.
3) always remember it's + to +, - to -. don't try to get "smart" and think they cross over or something, this will fry both your alternator.

also, if one set of jumper cables isn't allowing enough current flow (if you're jumping a big truck or something) you can double them up to get more current flow.

SumAznGuy · 12-20-2008, 04:19 PM

Another thing to do is, with the rescuing car running, and all the jumpers + and - hooked up, let the car sit for a few minutes to get some juice into the dead battery. If the dead battery has zero juice, the car might not start.

thumper · 12-20-2008, 04:30 PM

Quote:

Originally Posted by underscore

first you connect both - clamps, on the dead car it should be connected to a good chassis ground and not the battery. connect the + on the rescuing car to the battery, and start it. now take the remaining + and connect it to the battery, right as you do this start up the dead car. once it's running remove the + and the rest of the wires in the opposite order of install.

reasonings:
1) a running car can provide more current and more voltage than a battery alone
2) use the chassis to prevent explosions from the combonation of hydrogen gas + a spark.
3) always remember it's + to +, - to -. don't try to get "smart" and think they cross over or something, this will fry both your alternator.

holy crap i've been doing it wrong all this time

this is what i've been doing:

1. connect to + terminal on rescue battery
2. connect to + terminal on dead battery
3. connect to - terminal on rescue battery
4. connect to ground (engine) on dead battery

5. start rescue car and give it some moderate revs for a 1-2 minutes
6. start dead car

7. disconnect in opposite order from steps 4 to 1.

now... i've seen people not bother with step 4 and just let the clamp hang also, and the car will still start!

underscore · 12-20-2008, 08:08 PM

^ I've been told that trying to charge two batteries can be hard on your alternator due to the increased current draw, it's not designed to do that (I used to work an auto parts counter and this is what the mehcs/my boss told me). that's why you want to start your car then start the dead one right after.

I guess in theory not connecting the grounds could still work as this is DC. it's still good practice to connect it tho, if nothing else to keep the clamp from accidentally hitting the +

impactX · 12-21-2008, 08:00 AM

Quote:

Originally Posted by underscore

first you connect both - clamps, on the dead car it should be connected to a good chassis ground and not the battery. connect the + on the rescuing car to the battery, and start it. now take the remaining + and connect it to the battery, right as you do this start up the dead car. once it's running remove the + and the rest of the wires in the opposite order of install.

reasonings:
1) a running car can provide more current and more voltage than a battery alone
2) use the chassis to prevent explosions from the combonation of hydrogen gas + a spark.
3) always remember it's + to +, - to -. don't try to get "smart" and think they cross over or something, this will fry both your alternator.

also, if one set of jumper cables isn't allowing enough current flow (if you're jumping a big truck or something) you can double them up to get more current flow.

+ first, then -

thumper · 01-19-2009, 09:12 AM

i was watching MOTORING on tsn yesterday morning, and they were demonstrating how to jumpstart a car with a trunk-mounted battery... they grounded the negative to the shock tower mount in the engine bay. will the same work for an engine-bay mounted battery?

it's really hard to ground to the engine on my GTi because everything is covered in plastic

kuri · 01-19-2009, 10:16 AM

Here's a step by step from Edmunds:
http://www.edmunds.com/ownership/how...3/article.html

Tapester · 01-19-2009, 10:20 AM

As long as the terminals are hooked up properly going battery to battery is ok. Never start the dead car while the other is running. Very possible that you will blow the diodes on the good cars alternator. Let the cars sit for a good 2-3 minutes then shut it off, then try starting other vehicle.

thumper · 01-19-2009, 11:17 AM

Quote:

Originally Posted by Tapester

Never start the dead car while the other is running. Very possible that you will blow the diodes on the good cars alternator. Let the cars sit for a good 2-3 minutes then shut it off, then try starting other vehicle.

i've never heard of this before. goes against everything said above, including BCAA

Tapester · 01-19-2009, 09:37 PM

Usually you wont know untill a while after. The alternator still works but isn't charging properly. Worked at an alternator repair shop for a while, something they told me along the way.

thumper · 01-20-2009, 05:59 AM

Quote:

Originally Posted by Tapester

Usually you wont know untill a while after. The alternator still works but isn't charging properly. Worked at an alternator repair shop for a while, something they told me along the way.

damn. to think of all the damage i've caused then all these years