Vehicle Jumper Cables

Thread Starter

biferi

Joined Apr 14, 2017
226
If ever you See Standard Car Jumper Cables they Look so Fat and Thick.

My Sister got a Volkswagen Jetta and it came with Jumper Cables.

They are so Thin so what am I not Understanding?

What is the AWG of Standard Car Jumper Cables?
 

Audioguru again

Joined Oct 21, 2019
4,086
Maybe the instructions for the thin wires say to use them to slowly charge the dead battery from another car then disconnect the jumpers to start the car.
Maybe the VW motor is tiny and needs only a small current for its starter motor.
 

MrChips

Joined Oct 2, 2009
24,982
The bottom line is, what is the total resistance of the jumper cable, including the clamps?
The jumper cable should be short and fat to minimize the resistance. A longer and thinner cable provides more flexibility.
If the resistance is too high, it limits the cold crank current required to start your engine. For a small car, a surge current of 200-500A is sufficient.
 

BobaMosfet

Joined Jul 1, 2009
1,913
If ever you See Standard Car Jumper Cables they Look so Fat and Thick.

My Sister got a Volkswagen Jetta and it came with Jumper Cables.

They are so Thin so what am I not Understanding?

What is the AWG of Standard Car Jumper Cables?
What is her battery and starting system draw, max at start? You can test this with a clamp-on ammeter.
 

SamR

Joined Mar 19, 2019
3,807
I've seen a lot of cheap battery jumper cables burn their insulation off and not even begin to start the engine turning over fast enough to start. I haven't gone the route of Max but mine are very heavy duty and long. Long enough to pull in behind someone and jump them off. Anything else is a throwaway. Granted with today's EFI and computer-controlled engines they are easier starting and usually have less Cubic Inches that what I play with. A lot also has to do with the ampacity of the alternator. Mine is rated to crank out up to 100A.
 

Ian0

Joined Aug 7, 2020
4,054
Generally when a car has a flat battery, it is just slightly too flat to turn the starter motor. Only a little bit extra current is required from the second battery. That's why those boost starters that contain a 12V 10Ah VRLA battery can work.
Same argument applies to thin jump leads, though I wonder if connected to a really dead battery enough current could flow to overheat a thin cable.
My jump leads are in the @MaxHeadRoom style. I made them because we had a two-car garage with one car behind the other - if the one nearest the door has a flat battery, short jump-leads are pretty much a non-starter! The choice of crocodile clip is interesting - it has to get both enough pressure to go through all the dirt, and enough contact area for a low-resistance connection.
 

MaxHeadRoom

Joined Jul 18, 2013
24,192
Also similar to the battery terminal removal/replacement procedure, the first last jumper lead connection has a certain priority also.! ;)
 

Yaakov

Joined Jan 27, 2019
3,930
I have a good quality set of cables with some nice multi-jawed clamps on them. They've done well when I needed them. I paid more for them, but cheap ones are worse than junk.
 

BobaMosfet

Joined Jul 1, 2009
1,913
If ever you See Standard Car Jumper Cables they Look so Fat and Thick.

My Sister got a Volkswagen Jetta and it came with Jumper Cables.

They are so Thin so what am I not Understanding?

What is the AWG of Standard Car Jumper Cables?
Your meter isn't sensitive enough.
 

dcbingaman

Joined Jun 30, 2021
505
I would recommend buying a high quality pair of jumper cables from an auto parts store. Don't go cheap. Get the better ones at higher cost. They should be heavy duty extra thick wires and long enough to make it convenient to jumper another car if the car is parked adjacent to you. They will then last you a lifetime with no issues. I keep a good high quality pair in every vehicle I own in order to help others and to help myself.
When using jumper cables, always hook up the hot (positive) red connection first followed by the black one afterward. If you do it the other way around the positive will short on any metal of the car being the negative is tied to the car chassis. Never connect jumper cables while the engine is running. This is very dangerous. After they are connected, verify the jumper cables are routed away from any moving engine parts. Start the car that is working, finally connect the negative to the car being jumped last. Reverify that the cables are clear of any moving parts for both engines. Now you can start the dead car. When removing jumper cables remove the black one first. It is best if there is two people to disconnect from both engines being careful not to short them until they are safely removed from both engines.
 
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Ian0

Joined Aug 7, 2020
4,054
Do you believe that there is a good reason to connect the negative lead to the chassis away from the battery?
https://automyze.theaa.com/content/...t-your-car?category_name=car-maintenance-tips
I was told that it was to make sure that no sparks occurred next to the battery and ignited any hydrogen, when the first lead is removed, but the instructions say to stop both engines first, so there will be no hydrogen to ignite.
 

MaxHeadRoom

Joined Jul 18, 2013
24,192
When using jumper cables, always hook up the hot (positive) red connection first followed by the black one afterward. If you do it the other way around the positive will short on any metal of the car being the negative is tied to the car chassis. Never connect jumper cables while the engine is running. This is very dangerous. After they are connected, verify the jumper cables are routed away from any moving engine parts.
As I touched on in #11 also the same applies when changing a battery, always disconnect the negative lead first and reconnect positive first.
 

dcbingaman

Joined Jun 30, 2021
505
Do you believe that there is a good reason to connect the negative lead to the chassis away from the battery?
https://automyze.theaa.com/content/...t-your-car?category_name=car-maintenance-tips
I was told that it was to make sure that no sparks occurred next to the battery and ignited any hydrogen, when the first lead is removed, but the instructions say to stop both engines first, so there will be no hydrogen to ignite.
That can be a catch 22. If the car with the dead battery cannot hold a charge you will not be able to restart it after removing the cables. I like that article. I never thought about attaching the negative of the car with the dead battery to the engine chassis. I always connected it to the battery terminal itself. So maybe it is better to connect it to the engine chassis. I never did it that way but maybe it is safer like the article states? Does anyone have any advice about that?
 
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SamR

Joined Mar 19, 2019
3,807
And then there are those dreaded batteries with the terminal bolted down from the top with only the small bolt head protruding... Arrggghhh...
 
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