how long do you let the charging vehicle run?

[The motor guy]

This kind of goes along with my other thread, but I didn't want to derail it. Anyways, as recommended on here I bought some of those 1 gauge battery booster cables that are like 1/2" thick andt cost like 60 bucks. How long do you let the donor vehicle run when jump starting someone? I've heard if your cables are thick enough you can just start the vehicle without even running the donor vehicle, but we let it run for like 3 minutes at a high idle and my truck started right up.

 

[The motor guy]

The part that had me curious was that the cables on the donor vehicle side were pretty warm for the first two feet or so.

 

[14Accent]

You were smart to buy the expensive cables. It never ceases to amaze me what passes for "jumper cables". Average starter draw is somewhere between 150 and 300 amps, depending on application. Assuming the "dead" battery is truly dead, you would need at MINIMUM 4 gauge wire, with 1/0 gauge preferable. [censored], I use a light 1/0 gauge to power just the subwoofer amplifier in my car, which pulls right around 100 amps when it's cranking out. The heat in the cables is normal. Most likely due to resistance between the cable ends and the terminals. Did you jump the cummins in your signature? That thing will easily pull 250 amps while cranking.

 

[The motor guy]

Yeah. I was worried it wasn't going to work because the donor vehicle was a honda pilot with a tiny battery. I guess its the alternator that does the work though. I bet those cheap 8 gauge jumper cables would have melted.

 

[The motor guy]

It worked great and I was able to make the last ground connection to the lifting eye on the engine, which most engines don't have.

 

[eljefino]

I try for a couple minutes. I've read that the jump donor should confiscate the jumpee's keys so they aren't in there hammering on their starter... and your alternator. I tell the recipient to hold off until I rev it then go for it... I figure my revving helps spread the load over all the sets of diodes in my alternator vs just one. But I have fine luck with 10 gauge cables. When one looks at tables for amps and cable ratings there are assumptions about continuous use and voltage drops of only a couple percent. In reality if you can keep the suffering car from dipping below 9 volts or so during cranking, it'll catch. Bigger cables are better, sure, but if they come with stiff clips or a poor interface to the terminal posts it's a problem.

 

[Chris142]

I let it run 10 minutes or so.

 

[raytseng]

1. you can just attach the cars together. both off. wait 2 min then start the dead car. 2. only if thsts not working then you should start the donor car. 3. better yet just get a jump pack instead of jumper cables.

 

[michaelluscher]

I give it 5 minutes

 

[Linctex]

6 gauge or lighter cables I call "Charging cables". They will jump a vehicle with a battery that's .1 volt too low to start other wise. I did know a single mom who left her dome light on all night. She called me in a panic (from another state)... I told her she had to convince the person jumping her car it would take more than 5 minutes. It took 15 minutes to get her dodge caravan running again.

 

[Johnny2Bad]

With good cables you don't need to run the dead vehicle at all, but if you want to high idle for five minutes on the start vehicle it's OK. Turn everything off (lights, heater, radio, etc) on both unless you need the flashers going on the start vehicle. Be sure to run the dead vehicle for at least a half hour after a boost ("jump" for American readers) and blip the throttle up to at least 2000 RPM if you intend to just let it idle, since some alternators won't charge until they hit about 1600~1800 first briefly.

 

[Colt45ws]

Generally I try right away and if it doesnt work, I wait a few minutes with the booster vehicle running.

 

[The motor guy]

Originally Posted By: Johnny2Bad

With good cables you don't need to run the dead vehicle at all, but if you want to high idle for five minutes on the start vehicle it's OK. Turn everything off (lights, heater, radio, etc) on both unless you need the flashers going on the start vehicle. Be sure to run the dead vehicle for at least a half hour after a boost ("jump" for American readers) and blip the throttle up to at least 2000 RPM if you intend to just let it idle, since some alternators won't charge until they hit about 1600~1800 first briefly.

I've heard that, but I didn't think it would work since the battery on the booster vehicle is only a little bigger than a riding mower battery.

 

[HerrStig]

Output over time is what starts a car, not physical size. A lithium pack can hold a lot of charge in a small space.

 

[eljefino]

You want a surface charge on the dead battery. ~14 volts coming in on the cables does this faster than ~12.5. Having the electrons "that much closer" is beneficial.

 

[gathermewool]

Originally Posted By: eljefino

You want a surface charge on the dead battery. ~14 volts coming in on the cables does this faster than ~12.5. Having the electrons "that much closer" is beneficial.

Agreed. This will act to dampen the draw from the donor vehicle, since the highest current draw will want to come from the surface charge of the now not-entirely-dead battery. I've actually only had to jump several vehicles, so my experience is limited. I used to hook-up jumper cables with the donor car running and then immediately try to start the dead vehicle, in order to minimize the time the two charging systems were hooked-up in parallel. This never seemed to work on the first try, but did after charging for several minutes. It's important to note that most vehicles I've encountered that need jumping are dead as a doornail (e.g., a light has been left on for an extended period of time or the battery is simply too old or deficient, period.) I've never encountered a vehicle that was so low that it couldn't operate any electronics, but I've also never encountered a vehicle that could ALMOST turn over a vehicle. So, my new COA for jumping cars, should I need to, is how you mention, eljefino. That is, unless I have a multimeter on me that proves the dead battery has a shorted cell or something. The best solution: carry a jumper pack. I haven't had to use it, but I got one for Christmas a couple of years ago. I use it to charge my phone while traveling, but it's usually charged enough to use. I also have a smart-charger that has a starting feature. I hope to never need to use the feature, but we'll see. // Also of note, is I've seen people "jump" vehicles that were turning over perfectly. I've personally been asked for a jump by two people whose batteries were fine and the starter was turning over (at least initially) just fine. I think some people think that if the car won't start, it needs to be jumped. With that said, I've heard that people have actually started vehicles with a low battery that seemed to turn over fine, but with batteries that were actually too low to start the vehicle; so, unless you've got a DMM, maybe you can't simply rule out a jump being needed based on the other vehicle being able to turn over???

 

[JHZR2]

This is a good graphic for rules of thumb. The application is NOT "critical", 10% voltage drop is ok. I don't buy the hundreds of amps claim. Even on my IDI diesels, the starter is 1.7kW. That's 170A at 10V. Therefore the chart I show holds well enough. But it does all the same confirm the importance of bigger than 4ga for cranking. But 10ga to boost is useful in a pinch too. Won't work with a shorted cell in a battery, but will help revive a weak battery. A 4-6ga cable set is a good compromise for most gas engine cars...