A few questions about using jumper cables

[bullbreaker]

Heres a pair I made w # 2 , I believe I'd have too look welding wire about I'd say 15' to 18' long. Works great ! Have gotten vehicles jumped when other skinny store bought wires would,nt handle juice.

Boone

 

[kevinwak]

I took this pic earlier in the week. I borrowed an old Massey wheel loader from my dad to work on my landscaping. I happened to notice this field repair of a failed positive battery cable clamp!

Sent from my iPhone using TractorByNet

 

[alchemysa]

Its interesting this topic came up. Only today I had two instances that highlighted the shortcomings of jumper leads.

I was trying to start a brand new uninstalled diesel engine with jumper leads from a brand new 650 cca battery. The compression in the new donk was so high that even the brand new battery struggled to turn it over.

I think the main problem with jumper leads is not the thickness of the cables, but the very small 'contact' area of the clamps. If you think about it, theres not much point having thick, heavy duty cables if the clamps only provide a tiny contact area with the battery and engine terminals. To solve my problem I had to use two sets of cables, 2 earthing points, and wrap a thick wad of copper wire around the starter terminal. Ultimately I was able to greatly increase the clamping contact area and transfer enough 'juice' to turn the engine over. (A better plan would have been to connect proper 'bolt on' cables but I had none of those available.)

But before I even had a chance to sort out the problem above, my wife rang to say she had left her lights on in the shopping centre carpark and had a flat battery. (Yes it does have a buzzer!). Anyway, I drove down there and jump started her car with jumper cables and the new battery but it was very noticeable that even this new battery sounded almost 'flat' whilst using jumper cables. The bottom line is that the clamps are the weak link in the system. They usually have a very low contact area with the terminals they are clamped to. Its a bit like have a half inch nozzle at the end of a 2 inch pipe. If I hadn't known better I could easily have a thought the new battery was also flat.

 

[sandman2234]

There are some stores here that sell heavy duty clamps, and by using a decent size welding lead, a very good set of jumper cables can be manufactured by almost anyone. Take care when assembling them to get every connection tight. I made a set out of #1 welding wire and really liked them. When I needed a set to keep in the garage, I decided to use #2 welding leads for the optimum setup. A friend suggested that I stay with a max of 15' in length, rather than the 20' to 25' that I was thinking. I told him that I didn't think the voltage drop would be a problem for that size cable and he laughed. He grabbed a piece of he welding lead, did a rough guess on the measurement and handed it to me. I immediately realized that the weigh of a long set of cables would be detrimental to using them. The 15' cables are just about the right length for most situations. Long enough to reach most tractors from the back end, and even a Wife's car from behind (though it won't reach the batteries from the back side of my pickup).
A 650 cca battery trying to start any of my diesel engines via a set of jumper cables would be a laugh. My JD2555 came with two 550 cca batteries, which I replaced with a pair of 1025cca batteries. Nothing I hate more than a tractor that won't start, lol
David from jax

 

[SPYDERLK]

Thanks for the answers everyone.

Regarding attaching the neg. clamp to a ground rather than the battery terminal, Could you reverse this and ground the jumper cable on the car used to do the jumping, or does the good battery have to utilize both of its terminals?

You could, but its not necessary as you connect to the jumping car first. Since theres no power draw, theres no spark.

Also, using engine ground on the supply side imposes an additional loss in the circuit. This is avoided when you instead choose the ground connection on the demand side.
larry

... PS - Noted as also prior covered by reb

Grounding the jumper cable on the jumping car and connecting to the terminals on the dead battery would increase the resistance in the path to the starter. That would drop the voltage to the starter more than doing it the other way.