I agree. There are very few jumper cables that are of sufficient diameter and have sufficient clamping capability to start a diesel.

Most will simply "assist" the dead battery.

I've been in the situation of needing a jump on the SD and it's absolutely necessary to "charge" the weak battery for 15 minutes before attempting to start the engine.

The cables, by themselves, will never start the engine. The clamp has four points of contact to the post on the starter. No way that you're getting 250 amps though that setup.

I have a portable battery pack that will start my diesel with a completely dead battery, much easier than playing around with jumper cables (about $150 at the local McParts place).

How do you make a "good" connection with that pack?

Just a couple of heavy jumper cable type clamps, good enough I guess. I bought it and used it when my alternator died in TX last year and my battery was so dead that the dash lights and the gauges would not work. You definitely need to get a good connection.

I'm not kidding. A friend had a similar situation, I suggested "just try with that good battery"... see above.
If it does work, then get a new battery.
Good luck.

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83 SD

84 CD

This might be a successful endeavor at 50F or more. I don't think it would be successful at 20F. The required amperage to rotate the engine is much greater and the capability of the cold pack is much less.

Maybe, I haven't tried. I mostly carry the thing to help other people. If/when my alternator/battery dies again I'll give it a try. I still have some very heavy jumper cables in the trunk that I have used in 0F temperatures, but the battery pack is much easier.

I'd like to know how you make out at very low temps. My thought has always been that the four points on the clamp are the limiting factor...........but, the cable may also be significant.

Hopefully I'll never find out (new-ish battery and alternator at the moment), but if I have a chance to try it in the cold I'll let you know what happens.