Every mechanic has watched a car get towed in with a no-start condition, just to go out with quality jumper cables and start it with no problems. It happens so frequently that most mechanics grab a jump box or cables before anything else for no-start tow ins.
Usually, when this happens the customer states “I tried to jump it but it wouldn’t start”. Followed by getting upset that they had to pay for a tow bill, and diagnostics when all they needed was good quality jumper cables. Knowing how to jump-start your car doesn’t do any good without quality jumper cables.
Looking for Quality Jumper Cables?
When looking for quality jumper cables you must understand what you need before you can find the right set of jumper cables. Start with looking at the length and gauge you need. Then look at the clip style and quality. Past that it’s really a matter of finding what you need with the quality you want at a price that isn’t too high. However, we need to start with understanding what you need.
Ohm’s Law, Understanding How it Affects Your Cables
To understand what makes quality jumper cables, you need a basic understanding of Ohm’s Law.
Ohm’s law states that V=I*R. Whereas V = voltage, I = amperage and R = resistance. If you change the resistance then either the amperage or voltage will have to change. The same can be said with changing any of the other numbers. What’s this mean for picking jumper cables?
All cars must have a constant battery voltage, or they won’t start and run correctly. Hence the need for jumper cables when you don’t have at least 12 volts at your battery. When you have a constant voltage, Ohm’s law states that to gain amperage you must lower resistance.
It can take a lot of amperage to start a car. Depending on the engine and everything all things considered it can take 400 to 1000 amps to start a car. This means you must keep your cables resistance pretty low or risk not having enough amperage to start a car.
If your jumper cables can’t handle the amperage it takes to start your vehicle then you’ll be using to the cables to charge the battery instead of jumpstart it. This is why many times people will hook up jumper cables for a 5-10 minutes before trying to start the car with the dead battery.
Cable Gauge VS Resistance VS Length
When looking for good quality jumper cables you need to look for the gauge of wire they are made with. Wires gauges are backward to most people, the thicker the cable the smaller the gauge number. Thus 0 gauge jumper cables have a much thicker wire than a 20 gauge set of wires.
Both wire gauge and wire length affect the resistance of the wires. Think of gauge and length have a correlation. Longer wires have higher resistance, and lower gauge wires have less resistance.
Therefore the longer the set of jumper cables you buy the lower the gauge you must have to keep from raising the resistance. If you’d like to see how gauge vs length effect resistance Cirris has a great calculator for this. The general idea is that if you need longer jumper cables then you must buy cables with a lower gauge number.
Have Quality Clamps
Short heavy gauge cables with extremely low resistance won’t do much good. If you can’t attach them to the battery without high resistance. This means you need good quality clamps to match your jumper cables.
What you want to look for it a clamp that is all metal. Cheap plastic clamps aren’t going to do you any good. Past all-metal clamps you want to make sure they have are big enough to fully clamp on your battery post. Make sure they have good teeth and enough spring tension to hold the clamp tight on your battery post.
Getting the Right Quality Cables for You
How’s this all add up to finding a pair of good quality jumper cables? It’s simple when looking at buying cables you need to know how long you need them. Which greatly depends on where your battery is in your car.
You need a set of jumper cables long enough to reach a second car no matter how you are parked. If you could move your car easily you won’t need the jumper cables. You also want ones that are a heavy enough gauge that so you don’t lose voltage between the cars. It’s safe to say 20′-25′ feet long will take care of most cars and most places you may park.
The bare minimum gauge for a 20′ set of jumper cables is 4 gauge with 2 gauge being better. If you go to 25′ you really want to have a 2 gauge set of cables although you may be ok with 4 gauge. Remember you want as low resistance as is cost-effective. So seriously consider 2 gauge when going to 25′ long cables.
Many cables will have an Amperage rating also. This is normally a rating that explains how thick the insulation is on the cables. Car starters take a minimum of 400 amps, and trucks can go over well 600 amps. Thus the higher the amperage rating the better.
Conclusion
Lots of people own small short junky jumper cables. Then they wonder why they can’t jump-start their car when the battery is dead. Few people go out and buy the most expensive set of jumper cables they can find. After reading this article you should be able to pick out a quality set of jumper cables without having to spend more money than need be.
A great place to start is finding jumper cables that are least 20′ long and 4 gauge thick. However, 2 gauge and 25′ will make you happy. Along with making sure that you have a good heavy set of clamps on them so that you don’t have to worry about them. If you follow these simple rules you will never have to worry about your jumper cables letting you down.