Advanced Alternator/Battery Question...
Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
It would be an interesting experiment to see if the failure is in the electronics boxes going haywire or frying and hence, stopping the motor from running before the experiment is concluded with a "win".
Depending on the shape of the alternator, the quality of its output, and the ability of the key modules like PCM to deal with it --- my money is that it would die pretty close to instantly if the battery is removed from the circuit at idle if the vehicle is post 2003 on Ford cars.
PCM box have about a 2V spike tolerance from 14.5V... hmmm
A good experiment --- for someone with a late model junker.
The man from the road service thinks he's being helpful. After he can't jump start your car, he puts in his own known good battery and starts your car. So far so good -- your battery was definitely either run down or bad, and he's proven it.
Now he decides to "test" your alternator by disconnecting the battery. After all, the car's ignition should be able to run on just the alternator's power alone.
Wrong!
The moment he disconnects either lead from your battery, it's entirely possible he caused thousands of dollars in damage. Here's why...
Your battery does more than just yield electricity. It also shorts AC, spikes and transients to ground. Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. The ECU, the speed sensitive steering, the memory seat adjustments, the cruise control, and even the car's stereo.
Even if your computers and stereo remain intact, in a great many cases removing the battery burns out the diodes in the alternator, necessitating a new alternator. If disconnecting the battery interferes with the voltage regulator's control voltage input, it's even possible for the alternator to put out hundreds of volts, frying everything.
Even the initial premise was wrong. If you disconnect the battery and the car conks out, you don't know if it conked out due to insufficient alternator current, or whether the resulting transients caused your ECU (the car's computer, which controls fuel mixture, timing, and much more) to spit out bad data, shutting down the car.
Nobody should EVER run your engine without a battery.
And yet when you tell them not to, they'll roll their eyes. "I'm a professional. I do this every day. It's fine!" They'll sound so authoritative. So commanding. So intimidating. But they're wrong.
The problem, of course, is that disconnecting the battery doesn't always damage something. It does it only sometimes. Less experienced jump start professionals and automotive technicians figure if they got away with it a few times, it must be OK.
Don't let them do it on your car. When you call for roadside service, or take the car in for possible electrical problems, or have your battery and charging system checked at a "battery shop", give them this letter.
Don't Disconnect the Battery with the Engine Running
Cargo Master
Joined: Mar 2008
Posts: 2,569
Likes: 207
From: Washington
50% is actually pushing it with the loads people are running --- tuners, towing, no cooldown, heat...
You mean loads of over 50% should only be for short durations.
They can afford $1,000 bets, afford to be foul mouthed in making demands on forum members because of what they pay us to answer the questions.
You mean loads of over 50% should only be for short durations.
They can afford $1,000 bets, afford to be foul mouthed in making demands on forum members because of what they pay us to answer the questions.
You are correct, "ABOUT" should have been "Above".
I will edit it to clean up spelling issues.
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Freshman User
Joined: Apr 2006
Posts: 34
Likes: 0
Tiger Dan... Lets get this straight... This aint my first rodeo! i been coming to this site for about 5 years now. Ever since I got my 86 f-250. i found the help in here to be exemplary and was astonished to be confronted with such buffoonery. Also I didnt swear!!! I used abbreviated/misspelled english that left others to decipher what might have been said. Obviously you are a man like me and swears alot because you understood what I said. That would have flown right over my wife or mothers head. Calm down big boy!!!! Like I said its all friendly. I dont wanna offend or make waves. I appreciate your time and help.
As for another question goes...we are not in an auto shop!!! LOL!!!
As for a few other things go,,, I understand the bat is not a resistor but it has resistance. It is more like a buffer. And if you think that the alt only creates voltage you are dead wrong. The reg only allows voltage through but the amperage comes right of the rotor and the reg is connected to this field and the higher amp draws
burn the reg! ( source Alternator FAQ, Frequently Asked Alternator Questions answered )
" Never does the alternators amperage go through the voltage regulator. The area of concern when changing to a high output alternator is the amperage draw of the rotor. The voltage regulator does have a field amperage rating and because it has direct contact with the rotor you must be concerned with the amperage draw of the rotor. If the amperage draw of the rotor is greater than the rating for the voltage regulator the regulator will fail."
Explain this too then ... what the difference between a TOTALLY DEAD battery and no battery at all.?
As for another question goes...we are not in an auto shop!!! LOL!!!
As for a few other things go,,, I understand the bat is not a resistor but it has resistance. It is more like a buffer. And if you think that the alt only creates voltage you are dead wrong. The reg only allows voltage through but the amperage comes right of the rotor and the reg is connected to this field and the higher amp draws
burn the reg! ( source Alternator FAQ, Frequently Asked Alternator Questions answered )
" Never does the alternators amperage go through the voltage regulator. The area of concern when changing to a high output alternator is the amperage draw of the rotor. The voltage regulator does have a field amperage rating and because it has direct contact with the rotor you must be concerned with the amperage draw of the rotor. If the amperage draw of the rotor is greater than the rating for the voltage regulator the regulator will fail."
Explain this too then ... what the difference between a TOTALLY DEAD battery and no battery at all.?
Cargo Master
Joined: Mar 2008
Posts: 2,569
Likes: 207
From: Washington
<O
</OA totally dead battery will require max ALT output for a long time until it is charged. In theory the amps going into the battery will start to drop off as it gets charged up. Hopefully the draw/load will drop off before the ALT burns up. If you ever have to charge a total dead battery, say after a jump start, let the car just idle for 20-30 minutes as the ALT can not produce it full rated output at idle. It might just save you from burning up your ALT. This condition is even worse at night as the ALT will have to charge the battery and power all the lights.
<O
</OIf there was no battery or if you removed it after the jump start (in theory only, don’t do this in real life) the battery could not be a draw on the ALT.
Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
There would also be no valid signal via the sense wire.
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Freshman User
Joined: Apr 2006
Posts: 34
Likes: 0
I guess I gotta settle this myself then...If anyone disagrees with what i say then by all means reply.
Point#1
OK, so , lets get this straight then. The alternator produces both voltage and amperage. Voltage only travels through the regulator but the regulator is subject to the amperage field of the rotor and has a specific limit and will fail at constant high draws. Can we all agree on point 1?
Point 2.
A dead battery will kill an alternator? Can we agree on that?
Point 3
This is where I might lose some of you... A battery can test full voltage but still be low on amps. Can we agree on that?
Point4
If you battery is full volts and low on amps your alternator will try and charge. Can we agree on that?
point 5
You have a "VOLTAGE" sensing wire that comes off the alt to the battery. " NOT" a amp sensing wire. Can we agree on that?
So to sum this all up... when you remove a battery from a running vehicle the alternator simply believes the battery is dead and works its butt off to raise the charge in the battery so it can ease off the alts out put as the battery gradually builds up resistance to the current. The battery once reaching full charge provides the resistance/stability in the charging system that allows the alt to calm down and buffer any erratic electrical spikes. Can we agree on that?
I appreciate the help and lively debate.
Point#1
OK, so , lets get this straight then. The alternator produces both voltage and amperage. Voltage only travels through the regulator but the regulator is subject to the amperage field of the rotor and has a specific limit and will fail at constant high draws. Can we all agree on point 1?
Point 2.
A dead battery will kill an alternator? Can we agree on that?
Point 3
This is where I might lose some of you... A battery can test full voltage but still be low on amps. Can we agree on that?
Point4
If you battery is full volts and low on amps your alternator will try and charge. Can we agree on that?
point 5
You have a "VOLTAGE" sensing wire that comes off the alt to the battery. " NOT" a amp sensing wire. Can we agree on that?
So to sum this all up... when you remove a battery from a running vehicle the alternator simply believes the battery is dead and works its butt off to raise the charge in the battery so it can ease off the alts out put as the battery gradually builds up resistance to the current. The battery once reaching full charge provides the resistance/stability in the charging system that allows the alt to calm down and buffer any erratic electrical spikes. Can we agree on that?
I appreciate the help and lively debate.
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