Alternator Theory
CF Veteran
Joined: Dec 2011
Posts: 3,643
Likes: 1
If you would quit trolling me I would not resort to the ice cream thing.
Facebook is for adults acting like kids. So I pretty much don't care. Like your avatar.
If we would concentrate on wheeling and fun things we probably would not bicker so much.
Just a thought.
Facebook is for adults acting like kids. So I pretty much don't care. Like your avatar.
If we would concentrate on wheeling and fun things we probably would not bicker so much.
Just a thought.
CF Veteran
Joined: Nov 2010
Posts: 15,581
Likes: 8
From: some small town oregon
Year: 1989
Model: Cherokee
Engine: 4.0
If you stop giving dumb advise you would have a lot of members on here not giving you ****. And dude... the ice cream thing is dumb. My 90 year old grandma still eats ice cream at the Tillamook factory every summer when I take her there... so I have no idea what eating ice cream has to do with age
CF Veteran
Joined: Dec 2011
Posts: 3,643
Likes: 1
If you stop giving dumb advise you would have a lot of members on here not giving you ****. And dude... the ice cream thing is dumb. My 90 year old grandma still eats ice cream at the Tillamook factory every summer when I take her there... so I have no idea what eating ice cream has to do with age
Well obviously this is a lost cause.
My advise is honest and its my personal experience.
If you can not respect that, or others. Then that is your problem.
You go with popularity, I get it. Rather than just letting it be because you just may dissagree with me. Instead you have to get on here, cut me down, even though Its my personal experience. And you can not say for certain either way. Is it really worth it?
These things are so trivial in reality its not even funny.
CF Veteran
Joined: Dec 2012
Posts: 4,169
Likes: 6
From: York, PA
Year: 1998
Model: Cherokee
Engine: 4.0
CF Veteran
Joined: May 2008
Posts: 3,018
Likes: 23
Year: 1988
Model: Cherokee
Engine: AMC242
:brick wall:Here is what you fellows fail to understand. IF they system has the old generator. NON fuel injected. You can run it without a battery in most cases. No damage to computer.
It has nothing to do with 1974. Its the type of charging and electrical system a vehicle has. We are talking about jeeps.
IF the jeep has FI its alternator is powered by 12volts dc from the battery. The alternator will NOT charge without battery voltage present.
So it does not matter at all if you yank the battery cable off while its running. The alternator instantly will shut down and not damage anything. And your jeep dies
These systems are pretty bullet proof. A runaway alternator that is charging too much still will not hurt the pcm. YOu can jump start the car with another one and it wont damage the pcm.
There are tons of rumors on the net about damage could be done without a battery because its a "buffer" These people do not know electrical systems.
Salad, no offense buddy but you should have not skipped class
Transistors are what, class? That's right - "solid-state electronic devices."
A solid-state electronic device depends on a microscopic junction between two differently-doped silicon compounds (doped for extra electrons - "N-type" - or absent electrons - "P-type." The "P-N junction" is the basic building block of solid-state, it's what forms the diode.)
Considering the physical size of the P-N junction, it can be very easily wrecked outright by:
- Reverse voltage flow
- Overvoltage condition (HV transients, anyone?)
- Overcurrent condition
- Reverse current flow
- Excessive temperature (ever wonder why your computer has all those heat sinks in it?)
- Shonky connections (which can cause HV transients, heat unrelated to the operation of the junction, &c &c.)
- And other factors I'm probably forgetting.
However, the second & third points are what we're worried about. Disconnecting the battery in a running vehicle can cause HV transients (sometimes several hundred volts for a handful of milliseconds,) or high current transients (less likely, but can spike to over 200A - unregulated.)
Oops.
Once you get a diode in a critical circuit (and you have plenty of them starting in 1974 - in the ignition control module and in the back of the alternator...) you need to watch out for HV transients.
If a battery fails on its own, the system will often pick up the slack. A battery on its own cannot generate transients. But, a dynamo in the circuit damned sure can generate transients - and that's the problem here.
Don't think it can happen? Bud, I've seen it happen, and I've had to fix it. I've seen HEI modules that had exploded from HV transients, leaving just an empty hull.
Last edited by 5-90; Oct 24, 2013 at 06:23 PM.
CF Veteran
Joined: Dec 2011
Posts: 3,643
Likes: 1
Beg to differ - 1974 is considered the "cut-off" for that, because that's when solid-state ignition became universal. Transistor ignition, instead of breaker points.
Transistors are what, class? That's right - "solid-state electronic devices."
A solid-state electronic device depends on a microscopic junction between two differently-doped silicon compounds (doped for extra electrons - "N-type" - or absent electrons - "P-type." The "P-N junction" is the basic building block of solid-state, it's what forms the diode.)
Considering the physical size of the P-N junction, it can be very easily wrecked outright by:
- Reverse voltage flow
- Overvoltage condition (HV transients, anyone?)
- Overcurrent condition
- Reverse current flow
- Excessive temperature (ever wonder why your computer has all those heat sinks in it?)
- Shonky connections (which can cause HV transients, heat unrelated to the operation of the junction, &c &c.)
- And other factors I'm probably forgetting.
However, the second & third points are what we're worried about. Disconnecting the battery in a running vehicle can cause HV transients (sometimes several hundred volts for a handful of milliseconds,) or high current transients (less likely, but can spike to over 200A - unregulated.)
Oops.
Once you get a diode in a critical circuit (and you have plenty of them starting in 1974 - in the ignition control module and in the back of the alternator...) you need to watch out for HV transients.
If a battery fails on its own, the system will often pick up the slack. A battery on its own cannot generate transients. But, a dynamo in the circuit damned sure can generate transients - and that's the problem here.
Don't think it can happen? Bud, I've seen it happen, and I've had to fix it. I've seen HEI modules that had exploded from HV transients, leaving just an empty hull.
Transistors are what, class? That's right - "solid-state electronic devices."
A solid-state electronic device depends on a microscopic junction between two differently-doped silicon compounds (doped for extra electrons - "N-type" - or absent electrons - "P-type." The "P-N junction" is the basic building block of solid-state, it's what forms the diode.)
Considering the physical size of the P-N junction, it can be very easily wrecked outright by:
- Reverse voltage flow
- Overvoltage condition (HV transients, anyone?)
- Overcurrent condition
- Reverse current flow
- Excessive temperature (ever wonder why your computer has all those heat sinks in it?)
- Shonky connections (which can cause HV transients, heat unrelated to the operation of the junction, &c &c.)
- And other factors I'm probably forgetting.
However, the second & third points are what we're worried about. Disconnecting the battery in a running vehicle can cause HV transients (sometimes several hundred volts for a handful of milliseconds,) or high current transients (less likely, but can spike to over 200A - unregulated.)
Oops.
Once you get a diode in a critical circuit (and you have plenty of them starting in 1974 - in the ignition control module and in the back of the alternator...) you need to watch out for HV transients.
If a battery fails on its own, the system will often pick up the slack. A battery on its own cannot generate transients. But, a dynamo in the circuit damned sure can generate transients - and that's the problem here.
Don't think it can happen? Bud, I've seen it happen, and I've had to fix it. I've seen HEI modules that had exploded from HV transients, leaving just an empty hull.
Most all modern pcm's have protection against high voltage spikes. I was origionally wrong about the battery. It does act as a capacitor buffering voltage spikes. However its not the sole protection.
Continuous high amp loads with a open battery circut does have a potentially harmful effect on your pcm. As in it "could" do something. Still the cases are very rare because of the circut protection built in to the pcms.
In other words removing the battery cable while running will not do a thing except shut your car down.
I however in my own experiments and experience have found many solid state ignitions able to handle constant alternator power without a battery at all. We are talking hours of use without a battery!
To this date I have not had one failure because of this. I am not telling anyone to do this. It is just my experience.
5-90 you do not have to ever do what I do. Leave the risk taking to me
CF Veteran
Joined: May 2008
Posts: 3,018
Likes: 23
Year: 1988
Model: Cherokee
Engine: AMC242
Most all modern pcm's have protection against high voltage spikes. I was origionally wrong about the battery. It does act as a capacitor buffering voltage spikes. However its not the sole protection.
Continuous high amp loads with a open battery circut does have a potentially harmful effect on your pcm. As in it "could" do something. Still the cases are very rare because of the circut protection built in to the pcms.
In other words removing the battery cable while running will not do a thing except shut your car down.
I however in my own experiments and experience have found many solid state ignitions able to handle constant alternator power without a battery at all. We are talking hours of use without a battery!
To this date I have not had one failure because of this. I am not telling anyone to do this. It is just my experience.
5-90 you do not have to ever do what I do. Leave the risk taking to me
Continuous high amp loads with a open battery circut does have a potentially harmful effect on your pcm. As in it "could" do something. Still the cases are very rare because of the circut protection built in to the pcms.
In other words removing the battery cable while running will not do a thing except shut your car down.
I however in my own experiments and experience have found many solid state ignitions able to handle constant alternator power without a battery at all. We are talking hours of use without a battery!
To this date I have not had one failure because of this. I am not telling anyone to do this. It is just my experience.
5-90 you do not have to ever do what I do. Leave the risk taking to me
If the battery fails, the chances of having HV transients are almost nil.
If you manually disconnect a battery, the chances of HV transients approach unity (perversely - the better the battery is, the more likely they are.)
Things will run without a battery just fine - the nominal alternator output voltage is 13.6VDC (with an "acceptable" range of 12.0-14.4VDC,) and most automotive electronics are built for supply from 10.5-15.0VDC. So, yeah, you'll run just fine on the alternator only - until you have to shut down & restart.
I've seen a lot of trouble in 35 years of mechanical work (professional & amateur!) - some of it "designed in," some of it "not designed for," some due to "operator error," and plenty of it due to just simple wear...