Jump starting bad for alternator?

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Had to jump start the jeep this morning with my car. Took about 10 minutes to get enough charge to start. The jeep has a much bigger battery than my focus does. Will jump starting be bad for the alternator in my focu? Did I potentially damage it?
 
Only bad in the sense your alternator likely ran full fielded for a few minutes. Not much chance of damage, usually due to heat, running it at full output for a short time.
 
Just avoid starting the dead one while the live one is still running. That's when the largest current spike occurs, so you're better off not having the alternator involved in that.
 
If you cross the cables, damage could occur to both vehicles. Jumping batts works fine usually, the better cables flow current more effectively. If the charging source is good some times to pre-crank will help heating the cables. when the starter turns slow & stops crank its bad, burning the brushes on the armature.
 
It will put a strain on the alternator in the car with the dead battery. 90's Chrysler vehicles would not continue to run after the jumper cables were disconnected to avoid overheating the alternator if the battery was severely discharged.
 
When jump starting I always let the running vehicle run for awhile to get some juice to the dead vehicle. Then after awhile, I'll crank up the dead one, then disconnect everything.

Good positive (+) to bad Positive.
Good Negative (-) to bad Ground.
Run a bit (approx 5 minutes)
Crank up dead vehicle.
Disconnect cables in reverse order.

If the dead didn't get a good crank the first attempt, allow another 5 minutes run time before 2nd attempt.
 
Originally Posted By: dishdude
It will put a strain on the alternator in the car with the dead battery. 90's Chrysler vehicles would not continue to run after the jumper cables were disconnected to avoid overheating the alternator if the battery was severely discharged.



Yeah we had that problem. It's a 99 Wrangler 2.5L, I had to keep my foot on the gas to keep it running for some time after it started.
 
Rev the motor on the donor car when the crippled one is cranking. Alts have built in fans. Plus you'll get more amps that way and the odds are less of one diode taking the full load of starting the starter motor.

Jumping is one of those things where finesse meets impatience. A true BITOG jump starter would take the crippled car's keys before hooking up the cables so the donee has to sit and wait and follow instructions.

There are lots of bozos out there who would grab *your* cables and assume control. They can cross the polarity, arc the alligator clips... buffoons. If your car is running you call the show.
 
Originally Posted By: eljefino
Rev the motor on the donor car when the crippled one is cranking. Alts have built in fans. Plus you'll get more amps that way and the odds are less of one diode taking the full load of starting the starter motor.

Jumping is one of those things where finesse meets impatience. A true BITOG jump starter would take the crippled car's keys before hooking up the cables so the donee has to sit and wait and follow instructions.

There are lots of bozos out there who would grab *your* cables and assume control. They can cross the polarity, arc the alligator clips... buffoons. If your car is running you call the show.


Sadly, I've seen that happen too..
 
Most jumper cables are simply too thin, in combination with being too long. Combine this with today's "I want what I want and I want it now mentality" and an easy procedure becomes stressful for the jumper.

A quality set of 4 awg cables should be able to jumpstart a vehicle instantly without the donor car even running. Unfortunately most cables are 8 awg, or even 10 awg with really thick insulation.

I recently had an awful experience when asked to assist somebody who had no jumper cables. I had no cables per say, but I have some 10 awg cables with alligator clamps from my 20 amp air compressor and 25 amp battery charger that I can join to make a poor set of jumper cables.

I informed the person that I could help, but it would likely take in excess of 20 minutes for the thin, long wiring to pass enough current to allow starting.

I hooked it up, and the guy instantly jumps behind the wheel and tries cranking it.

I saw his intent and rather than have him melt my wires, I disconnected them, and he got all PO'd.

We exchanged some words, and long story short, I took my cables and drove away, because If I didn't leave, I was gonna send the guy to the emergency room.


Can you imagine cursing at someone who was trying to help you?

I always try to help when I can, but some people........
 
I've also jumped cars with my high quality thick cables when others didn't work. don't scrimp on high quality jumper cables.
 
With the engine in the donor at idle, the alternator will be fine. It's not able to produce full output at idle, even at full field, so overheating the diodes shouldn't be an issue, particularly with better airflow from the hood being open. However, if it's revved up and can attain full output, the story may change.

As far as the Jeeps not staying running, my Mom's 99 Grand Cherokee 4.0 did the same when the battery went (dead cell), even though it had just enough juice to get it started without a jump. Had to drive the first mile or so to the store for a new battery (my Jeep had a bad water pump) two-footed to keep it from stalling. After about a mile, it idled fine for the rest of the drive. I didn't know it was a design feature. I thought it was just a common glitch.
 
Jump starting bad for alternator?

As long as there are no crossed polarities, no shorted electrical system or shorted cells, and no extended cranking on the rescuee... there will be no immediate damage. The extra heating created in the donor vehicles alternator will be a small negative influence on it's life. I agree that the donor should be at high idle to maximize the alternator cooling fan output.


A little
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Any one remember maneuvering the vehicles bumpers together, then using a dogleg jack handle (or two) positive to positive on the batteries in the absence of jumper cables?
With patience and practice this works on some vehicles with METAL bumpers.

Yes I am old enough to remember this....barely that is.
grin.gif


Rickey.
 
A simple method to prevent damages is to run the donor car for a while at high idle to charge the dead car a bit but then shut it down while actually starting.

I personally NEVER run my car while jumping someone else. It is fraught with peril, and all outcomes are expensive.
 
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