Many "consumer grade" jumper cables have reduced copper and added extra insulation to make the cables look as thick as better cables. Long ago I invested in a long, very heavy set of cables, and a decent zipper bag to store them in. Never regretted it, and the bag has done it's job by protecting the cables between uses. The only other item in the bag is a pair of safety glasses, just in case. They have never failed to start a car immediately after connecting. And I do insist that anyone without eye protection takes a few steps back. ;) On 5/16/12, Dwayne Reid wrote: > At 12:54 PM 5/15/2012, Eric Kort wrote: > >>1. The resistance of the cables is too high to deliver the needed >>current to start the dead vehicle. (It seems if that were true, >>someone would be out there selling uber-cables that don't have this >>problem, but I don't recall seeing such cables.) > > Yep. The starter needs significant current to operate. > > >>2. The dead battery is a low impedance current sink while it is >>charging, sucking away the available current from the higher impedance >>starter until it is charged enough to start the car on its own. > > Also Yep. A discharged Lead-Acid battery that is otherwise in good > shape (not sulfated) has an extremely low impedance and will consume > just about as much current as you can give it. That causes > significant voltage drop in the jumper cables, which contributes to (1) > above. > > >>And while we are on it, why does the owner's manual suggest connecting >>the negative end of the cable to the engine block of the dead vehicle >>(doesn't the engine have continuity with the negative terminal on the >>battery--making it simpler from a procedure point of view to just >>connect the battery terminals on both vehicles)? > > A battery that is being charged at a high rate gives off Hydrogen > gas. You want to keep sparks as far away as possible from that gas. > > > I had an unfortunate incident during High School where I was in close > proximity to a rather large car battery that was being charged. The > charging lead became dislodged somehow and the battery promptly > exploded. Luckily, the lab was in fairly close proximity to the Gym > showers and I was quickly dragged to where I could be rinsed off. No > damage done, other than to clothing. Large holes did appear . > > dwayne > > -- > Dwayne Reid > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > (780) 489-3199 voice (780) 487-6397 fax > www.trinity-electronics.com > Custom Electronics Design and Manufacturing > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .