Quantitatively, how sucky are my jumper cables, and can I tell if I've made them better?

Factual Questions
1

After using my jumper cables in various situations, I have determined that they suck, since they’ve worked perhaps once in a 1/2 dozen uses. (Other cables work first-time-every-time).

I think it’s due to a combination of being only 1/3" thick and 12’ long, but can I actually test this? I’ve soldered the ends a bunch (they were just crimped on to the clamps before), but the resistance on the cables still registers the bare minimum on my multimeter (makes sense really, it’s only testing a tiny charge on a copper cable).

I also don’t really understand why there’s a problem; 120v cords have much thinner cables than this and they work just fine. Isn’t that a lot more juice? :confused:

2

You need bigger diameter wire for a 12 volt DC system for the same amount of power transfer you get with a 110 volt AC system.

3

120V is a higher voltage and lower current, smaller wires are fine with that.

is that 1/3 inch the wire or the outside of the insulation?

doing good soldering on large cables takes some doing to have it be correct. doing it poorly can make it worse.

having the clamps be shiny metal on the inside edges of the clamps and the battery posts or clamps is important.

4

On a scale of 1 to 10, your cables suck an 11.

Get some of these. 12’ x 6 gauge. Best 40 bucks you will ever spend.

5

8 gauge wire is the bare minimum for decent jumper cables. 6 is much better, but stiffer and more expensive. 4 gauge is better still.

6

A quality set of 2-gauge jumper cables will cost at least $60, and are worth every penny:

http://www.arizonatools.com/tools/jumper-cables-booster-cables/detail/JUMPERCABLES/

7

Seriously, don’t drive around with shitty jumper cables. When you need them, you REALLY need them - if they fail you might as well have left them in the garage. Especially if you have a car where you need to use them more than once in a blue moon, which I assume you do otherwise we wouldn’t have this thread.

8

I picked out this example over some better ones at around the same price, because of the web site problems of linking them.

Minimum good jumper cable that will work.

Why this:
20 foot length - You can reach a vehicle with another in the way.
4AWG copper wire - handles 500 amps
Sturdy clamps - The clamps are thick metal so jaws don’t move sideways and pop off.
The clamps have a heavy duty spring for closure
There are copper teeth attached to the clamp jaw reinforcing the clamp jaw.

9

Most of the jumper cables you can buy at anything close to a reasonable price are at best barely adequate to do the job. In addition to their obvious faults, the insulation used tends to become very rigid in freezing weather.

More than 30 years ago, I went to a welding supply house and bought 25 feet of #2 welding cable (incredibly flexible due to many tiny strands, pure copper - at a time when jumper cables were made of aluminum - and a rubber jacket good to well below 0 degrees F). I also got 4 copper welding clamps and a pair of clamp boots each in red and black, and soldered the whole thing up to make an indestructible 12-foot jumper cable set. I’ve moved this cable through 8 cars in 30 years and it is still working perfectly. It was also less expensive than the cables you could get at the auto center.

Here’s a picture of the inside of a #2 welding cable: picture

It looks like Coleman Cable is selling “Booster Cables with Welding Cable Construction”, but i still like mine better. Even the “Royal Excelene” welding cable that Coleman itself sells is better - 644 strands in #2 welding cable vs. 119 strands in their #2 booster cable, so a lot more flexible, as well as a real rubber jacket instead of TPE.

10

1/3" is measuring outside the insulation. (I can’t fit my micrometer in where the cable meets the clamp, and I’m not sure how “squished” it would have to be to be right.) I’m guessing the gauge is from this chart? It’s hard to tell exactly where mine fit, but they weren’t very expensive, so probably not that great.

From the replies (thanks all!), it looks like the only way to make these any better is to splice some extra wire alongside the existing wire.

Oh, and I see the word “Ampacity”. Is that the quality that needs improving? It doesn’t look like something I can measure… in fact from the link it looks a bit subjective. :dubious:

11

As others have said, at lower voltages, you need thicker wire to pass high current. Even though a household extension cord can even sometimes power up a toaster or space heater, you won’t get that at 12 volts.

Also, the longer the wire, the thicker it needs to be.

There are six- or maybe eight-foot jumper cables, that are only good for jump-starting cars nose-to-nose, or side-by-side if your battery and their battery are each installed on the near fender. If each battery is on the far fender they might not reach. Forget about these short cables, avoid them.

12-foot, six-gauge cables are great for jumping two cars side by side, even if the batteries are on the far sides of the engine bay, and even if your (or your Good Samaritan’s) driving skills don’t allow to park the cars very close together.

If the dead car is nose-in in a parking lot, it’ll usually have to be pushed out of the space in order to use the 12-foot cables.

20-foot, 4-gauge cables will work in just about any situation, including jump starting another car from behind.

If you’re strong enough to push a car, and/or on a tight budget, get the 6-gauge 12-footers—that’s what I have.

Unless you’re really broke, I wouldn’t bother trying to fix up your old cables. Wal-Mart has several good, inexpensive sets. Places like AutoZone and Pep Boys also have good cables, but tend to charge more.

Also, don’t forget that no matter how good the cable, you need a good connection. Most of the time, the battery terminals on the cars will be rusty, dirty, or corroded. You’ll want to rock the clamps back and forth several times to scratch and clean the surface for a good connection.

P.S. If you do stay with your thin cables, you can make some improvement by letting the “good” car run for several minutes, with all of its accessories turned off, before trying to start the dead car. The dead car’s battery will be at least partially charged, lessening the amount of current you have to pull through the cables during starting.

12

Just buy new ones. Don’t mess around doing silly things like trying to splice wires in parallel.

And don’t solder. Solder connections don’t hold up well in environments where the material expands and contracts a lot (like jumper wires which are left in a car all year round and experience a very wide temperature range). Your OP indicates that you don’t have a lot of respect for crimped connections (“they were just crimped”) but crimp connections actually work a lot better than solder for this sort of thing.

The current carrying capability (ampacity) of the wire isn’t subjective. It’s related to how much the wire heats up, which is a function of how thick the conductor is and how thermally conductive the insulation around the wire is. Thicker wire carries more current before overheating.

And by the way, always make the last connection to the car frame, not the battery.

13

Well, there are actually *two *current limits for a wire or pair of wires:

  1. Above a certain current, the self-heating (P = I[sup]2[/sup]R) of the conductor will get high enough to damage the insulation.

  2. Above a certain current, the voltage drop (V = IR) will get high enough that there won’t be sufficient voltage at the other end of the wire(s).

Length is not a factor in #1. Length is a factor in #2. The current limit for #1 may be higher or lower than the current limit for #2. Generally speaking, you should calculate both current limits for a given wire or pair of wires, and stay below the lower of the two. If you need these limits to be higher, you must use wire(s) with a larger cross-sectional area.

14

Is it time for me to tell my tale of when I couldn’t get jumper cables to work, I took the battery out of one car and turned it upside-down, matching the proper terminals, on top of the battery of the other car? It worked, too…leaked some acid, but worked.