@ Jason (post #25) — Yes, leave everything connected until both cars are running, then disconnect.

If you receive a jump, you should always get to the bottom of it, and determine why you needed a jump. If you have an older car and just left the lights on (maybe a rainy day, when it’s just easy to jump out of the car and walk away), it’s easy to know: you let the battery drain, and your electrical system is probably fine. But if there is no obvious reason, some trouble-shooting is in order.

Corrosion on battery cable/terminal connection, and/or loose cable connection? This is very common, and I always at least try to test the tightness of the cable/terminal attachment by trying to twist the cables on the battery posts: if I can move the cable, it’s loose, and that’s likely my problem. If I don’t have tools with me, I’ll try to twist and push them down on the post to try to get the best connection I can, and clean and re-attach them when I get home, which costs nothing but some time.

Any time I receive a jump I always check the date on my battery: this should be recorded in the glove box for easy reference, but it’s easy to forget how much life is still left in them: if it’s close to the “expiration date”, it’s time for a new battery, because this one is close to the grave. In my experience, they usually fail uncannily close to their expiration dates.

Driving the jumped car for 20–30 min. after it starts allows the alternator to begin charging the battery again to the point where it can reliably start the engine on its own. I ensure my battery is sufficiently recharged by driving for 20 min., and when I have a bit of open road ahead of me, slipping the transmission into neutral, shutting off the engine, then trying to start the engine while I’m moving along at at least 30 mph. If the car starts, I go home; if it doesn’t, I bump-start the car on the fly by leaving the key in the “On” position, slipping the transmission into a high gear, and releasing the clutch. (Never remove the key from the steering column of a moving car: the steering lock will engage at the slightest movement of the wheel, and you will have no steering control). If after 45 min. and several attempts go by, and the battery still cannot start the car, at least it’s still running, and I head to the shop, because either the battery will not accept a charge, the alternator is not generating current, or the regulator is not allowing the current produced by the alternator to get to the battery. In any case, it needs a mechanic with diagnostic tools. This ability to bump-start a moving car is an advantage of the manual transmission: it cannot be performed with an automatic transmission.

If I had a car with an automatic transmission, I’d drive straight to my mechanic’s shop (make it at least a 20-min. drive), and try the independent start there. Pull all the way in: no sense driving all that way just to have it fail to start on the curb. That way, if it fails, you’re already at the shop and have avoided a tow.

Of course, a AAA card is probably the most valuable tool to carry in your car. I mean, if you want to depend on other people on some rainy night. :)

In response to post #10, I’ve never heard of a car that won’t allow the alternator to charge the battery if the light switch is not turned to “On.” If any car were built this way, and you only used your car during the daytime, you’d have a flat battery eventually: even if the alternator is supplying all the electricity needed for the ignition system, the battery would still have to supply power for starting the engine and for accessories like radio, etc. There must be some misunderstanding there.

Regards,
Sander, The Netherlands.

Something that has improved my ability to utilize my jumper cable over the years, is that I bought mine with extra long (16 ft.) cables.

Depending on the location of the batteries, a short cable length can be a deal breaker when it comes to giving a car a jump.

So do you leave the cables connected when you start the stalled car too?

Just leave everything connected until both cars are running and then disconnect?

cheap jump cables are mostly way too slim, its ok for small gasoline engines in hot weather. But on a freezed car or an Diesel engine they mostly wont work.

I guess it could be either not finding a clean metal surface, or less resistance because of a direct connection to the battery.

I also understood while doing it that I was taking a risk — I just tried to be deliberate about it so as to reduce the amount of sparking.