Troubleshooting jumper cable failure Q:

My question deals with jumping a dead car that has not been started for over a month. The battery is eight months old. I tried jumping the car with no success. I had good cable contacts on both batteries and had the running car idling at 2,000 to 2,500 rpm (sometimes higher but not over 3,000 rpm) for several minutes before trying to start the dead one. And I kept it at high idle throughout the process. All I could muster was enough power in the dead car to get something to continuously click and a few lights to come on. I just could not get enough cranking amps into the dead car.

I tried another host car with the same disappointing results. Periodically, I would rejiggle the cable claws to make sure I had a good battery contact. The temperature was about 80 degrees. The next day when the tow truck came, he just connected his portable battery jumper box to the dead battery and it immediately started! Evidently the portable unit was providing way more cranking amp power than jumping between two cars.

So is there anything I could have done in the jumping process to increase the odds of success? Or should I invest in a real good portable unit (>500CCA) and throw the battery cables out? The cables were middle of the road quality and on the long side which may not have helped? I assume shorter and real heavy gauge are best to prevent amperage loss?

A: It sounds like you applied sound procedures in your jump starting attempt. My hunch is possibly the nonstarting vehicle had a dirty battery terminal connection and the service provider raked one or both of his/her cable clamp sides across the top of the battery posts, the other side of the clamp on the battery terminal, circumventing the poor connection. Or one of your jumper cables suffered from a poor connection within one of the clamp/cable assemblies.

BRAD BERGHOLDT

Heat is a great indicator of electrical resistance! You are correct: Short and thick is best on the cables. I’m also a fan of portable jump start units. Thanks to modern battery technology they’re lightweight, robust and convenient. Perhaps other readers can share recommendations for units they are pleased with.

Ireceived several comments regarding the recent column about battery testing and replacement, and there are certainly many ways to approach this and other situations. Here are a couple of the comments:

“Why wouldn’t you just call AAA. They will not only come to you, but they will also check your battery condition and your whole charging system. If a battery is needed, it can be replaced right then and there. Plus they have a three-year warranty. And if you have any problem starting your car after that, anywhere, AAA will send a tech to wherever you are to recheck it. To me it’s a nobrainer. Check it out!”

“Your advice was good, though I would disagree with taking the battery to an auto parts store for a conductance test. Those tests and testers are notoriously inaccurate. What is needed is a real load test with a good old fashioned battery tester that puts an actual load on the battery. In the circles I run in, no one will trust one of those tests. And most especially if they say the battery is good.”

I agree about the merits of a battery load test, if it’s performed properly on a fully charged battery (that’s the fly in the ointment). Given the opportunity I like to run both a conductance test and a load test, to be as sure as possible of a battery’s true capabilities!