How to Choose Quality Jumper Cables
Every mechanic at one point in his life has watched a car get towed in with a no start condition. They then go out and jump-start the car, with no problems. Usually when this happens the customer states “I tried to jump it but it wouldn’t start”. This is because the customer didn’t have good quality jumper cables, and everyone should know how to choose quality jumper cables to keep in their vehicle.
To understand what makes quality jumper cables you need a basic understanding of Ohm’s Law. Ohm’s law states that V=I*R. Where as V is voltage. I is amperage, and R is resistance. What’s this mean for picking jumper cables?
All cars run off of battery voltage. For ease of understanding we will call battery voltage 12 volts. In reality it’s 14.1 volts when your car is running and 12.4 volts with a charged battery.
With a set voltage Ohm’s law means that to gain amperage you must lower resistance. Since it’s takes a lot of amperage to start a car this means you lower your resistance. Thus when looking for quality jumper cables you want ones that have the least resistance.
Cable size VS Resistance
A set of good quality jumper cables will tell you the size of wire they use. Wires are listed in AWG. AWG stands for American Wire Gauge. This will sound backwards but the thicker the cable the smaller the gauge number. Wire size and length effect its resistance. Therefore the longer the set of jumper cables you buy the lower the gauge you’ll need to keep from having too high of resistance. If you’d like to see how gauge vs length effect resistance Cirris has a great calculator for this.
Getting the right set for you
How’s this all add up to a pair of good quality jumper cables? It’s simple, when looking at buying cables you need to know how long you want them. This depends on where your battery is in your car. However it’s safe to say 20′-25′ feet long will take care of most cars and most places you may park. You need a set 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 loose voltage between the cars. Thus the bare minimum for a 20′ set of cables would be 4 gauge with 1 gauge being better. If you go to 25′ you really want to have a 1 gauge set of cables although 4 gauge will do.
Many cables will have an Amperage rating also. Car starters take a minimum of 200 amps, and trucks can go over 600 amps. Thus the higher the amperage rating the better. Although most of the time if you don’t have enough amperage rating in your cables you will be ok since you won’t be cranking for long unless you have bigger problems that a dead battery. If they don’t have a listing for amperage or they are under 600 amps, don’t worry. The amperage rating is really more of a rating of how good the insulation around the wires are than how many amps they can handle.
So many people have little junky jumper cables and wonder why they can’t jump start their car when the battery is dead. Other people just go out and buy they 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 1 gauge and 25′ will make you happy. Also make sure that you have 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.