I'm making my own jumpers and noticed most commercially available motorcycle jumper cables are 8-10 gage wire. Of course, I want to go with the lightest gage possible without melting them. Some people use a standard indoor extension cord (14 gage). The cables on my charger with the "boost" feature use 16 gage. Am I safe to assume that 16 gage is heavy enough wire for this since my charger can be used to jump start a car?

 

Well.. The thicker the wire the more power will be available and the less the loss and the less the amount of heat that will be created.

Also the length will be a factor, a shorter cable can be thinner (not that it is really a good idea)

Just because you can replace all the wheels on your car with doughnut spares it doesn't mean you want to.

edit: This guy used 14 gauge for 6 ft: http://www.gadgetjq.com/cheapcable.htm I would use as thick as I could fit in what I was packing things into.

 

No, 16 gauge wire is not thick enough to jump start a car... It's thick enough to add enough juice to what the battery already have to start a car...

If you try jump starting a car with a 16 gauge the cable will get hot enough to melt the insulation and short out...

A 16 gauge wire is rated to transmit 10A maximum (during a very short time)... The average starting load on a Superhawk is 20A... So one of three things will happen...

1. If you have a good battery on the other end, you might get the hawk going after a few tries...

2. Or since the thin cable robs enough juice, you have to keep trying for several attempts and the battery in the good bike is flat and now you have two dead bikes... (Most bikes don't charge at idle, so having the engine on doesn't help unless you rev it, which is bad for other reasons...)

3. The cable gets hot enough from the repeated attempts that the insulation melts and you get a short. Now you have two very, very dead bikes...

The chance of 1 is 50%, the chance of either 2 or 3 is also 50%... Your choice, but I'd use a thicker wire...

The reason I know this is that I for one work as an electrical engineer... Two, I have made myself a couple of battery packs to replace the heavy stock battery and I then looked at the fuse (30A) and measured the starting load to around 20A and at the most 25A...

A 8 gauge wire is rated for 24A... 10 gauge is rated for 19A... I'd say for jumper cables 10 gauge will be good, 8 excellent and possibly for very short leads 12 gauge works, but less than that and you are risking problems...

And yes, other bikers might get away with less, as their bikes are easier to start, drawing less amps...

 

If you feel you want to test it... Take a single wire of 16 gauge and connect the positive pole on your battery to the cable harness in the bike and try to start the bike with the saddle of... Hold the cable in your hand and you will feel the cable become warm... Don't worry, it's safe... The bike is unlikely to start and you wont get any short circuits as there are no two wires close to each other... Worst thing that can happen is you get a hair raising experience if the cable melts...

 

This was a good question. I think I will make a set for myself too. thanks.