Home Made Jumper Cables - Question

[Newt]

Question for electrical guys. Was at the hardware store and noticed you can buy small clips of various sizes that would fit a battery terminal. Over to the wire section and they have lamp cord, etc. Seems to me for around $10 you could make a set of compact jumper cables to carry. Is there any reason lamp cord would not work for the cable or some other smaller guage wire? Standard cables use a very large cable, but don't know if smaller wire would work as well or what the safety or other advantages there are in using the heavy duty cable.

[Joe Frickin' Friday]

Is there any reason lamp cord would not work for the cable or some other smaller guage wire?

 

Two problems:

 

1. it won't carry enough current (too big a voltage drop due to high resistance of small cable), and

 

2. It'll melt.

 

Well, OK, the copper wire might not melt, but if you're cranking for any length of time, it might get hot enough to melt/burn the insulation...and if that happens, the wire might short with something else metallic (like a car fender), and that's when sparks will fly. And if the short persists for a significant length of time, the batteries might get really, really angry (think "flaming explosion of hot lead and sulfuric acid").

 

Now that we've described the worst-case scenario... Here's some seat-of-the-pants advice:

 

On cars, there are typically two cables going to each battery terminal, a fat one and a skinny one; the fat one powers the starter, and the skinny one powers everything else on the car. IIRC, our bikes are configured the same way. So if you're looking for a rough guideline on how big a wire to use for a jumper cable, check the fat cables going from the battery terminals down to the starter. Keep in mind those cables are sized for a run of maybe 18 inches (from battery to starter); if you're looking to make six-foot long cables, you definitely don't want to go smaller than that, and you'd be wise to consider using larger cables, otherwise the voltage drop will too great when the starter tries to draw monster-current through that cable.

[Mike O]

Cycle Gadgets sells a 10' jumper cable that is advertised to work for the RT. 10 gauge, already terminated with clamps and a storage bag. For $12.95. Might be more cost effective than building your own.

 

 

Regards,

 

Mike O

[johnlt]

If you use smaller cables than those mentioned by Mitch, it usually helps a lot to hook them up with the "source" vehicle running for a while prior to trying to start the bike. That will help charge the bike battery a little and can make a real difference.

[Newt]

Thanks. Looks like the Cycle Gadgets set is the way to go.