Alternator problem

You don't get it, and appear unable to understand what you are doing. There is no reason for you to continue to post here, you only hear what you want to hear, not what we are saying.

NO one said 'extended'. No one said 'briefly' either. YOU SHOULD NEVER, EVER, DISCONNECT THE BATTERY FROM A RUNNING ENGINE. Doing so can damage both the alternator's electronics and the other electronics in the car.

You don't remember those boxes (as see on TV) that provided full battery voltage on the field coils to provide 120VAC RMS to power drills, lights or whatever (whatever being stuff that doesn't require AC, of course)? I never bought one, but probably someone here did.

They didn't tell you in the ads, but I think you'd have had to rev the engine considerably to get full mains voltage.

Best regards, Spehro Pefhany

The ones I had seen from JC Whitney years ago came with a manual throttle cable that would override the car's accelerator pedal so you could set (screaming) high idle. You would increase RPMs until an indicator lamp came on... Also included a regulator which substituted for the original external regulator and basically connected output to field (assuming a grounded field on other end) and chopped the field when desired voltage was reached. Needed a transfer switch to disconnect the battery and alternator output was connected to a power outlet. Output was 120V but since power was taken from an otherwise unmodified alternator, DC. Field winding was also seeing something like 40V so windings and brushes tended to have short lives.

That was back in the day when alternators used (generally) 200 PIV or higher diodes. These days, I believe that they use much lower voltage units with lower conduction losses.

If your variable speed drill used a triac control (which all did at the time), would just run at full speed.

Only sane way to do this today is to use an inverter to get 120V (and AC to boot). Oppie

You are rapidly proving you don't understand alternators. ...Jim Thompson

"Oppie" wrote in news:BXHLp.11348$ snipped-for-privacy@newsfe09.iad:

Pulsating DC.(but still unhealthy for transformers.)

perhaps Schottky diodes? lower PIV but handle high currents.

You might get 120 volts AC from a modified car alternator,but it's not going to be 50-60 Hz AC. Anything using a transformer will overheat or burn up.

"Standard" alternator is 3-phase, full-wave rectified. I have heard of people re-winding them to get 120VAC. ...Jim Thompson

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So, you are saying the atlernator is dumping 400V * 30A or 12000W into the load?

You still don't get it..

Jamie

So, you are saying the atlernator is dumping 400V * 30A or 12000W into the load?

Are you really that stupid? Or just imitating skyturd?

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well as long as the load doesn't change, the voltage shouldn't change i.e. if the 20A load isn't the battery there shouldn't be a voltage spike where should it come from?

if you go buy a kill switch for a race car it comes with a ~3R resistor, I assume that is what they think is sufficient to shunt the current that might be charging the battery

-Lasse

Jim Thompson wrote in news: snipped-for-privacy@4ax.com:

You still won't get 50-60 hz out of one,unless you manage to spin it at the right RPM and have scaled the new windings to produce single phase 120V AC at that RPM.

Highly unlikely.

you might as well buy a proper generator. (and get more power and the right freq.)

any

_Where_ did I say that?

But Confucius did say, "He who runs alternator without battery be big fool" ;-) ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

It is the connect/disconnet that will kill the avalanche diodes in alternators. My chevy truck has two terminals on the Bat + with a lead spacer. Turns out the lead spacer deforms over time with temperature cycling, causing a bad connection. Pop, bad diode as a result. Took out the lead washer, no more bad diodes ;D

Cheers

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You are agreeing with him.

I am just disagreeing with his claim that hundred of volt is surging into my load. So, tell me. What is the voltage surging into my 0.5 ohm load, with the head light on?

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Suppose you have an alternator outputting 30A into your battery, because it is discharged. If you suddenly remove the battery it IS possible for the alternator voltage to rise to 400V... I've seen it. Any accessory directly attached to the alternator is likely to get smoked. In the mid '60's my design requirement was for my regulator to survive that 400V spike... no matter that it may well kill the mechanic who lifted the battery cable... I kid you not, I probably still have the spec in my files. ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

As I recall, some high end cars had an option for the Sierracin windshield de-icers (like the ones used on commercial aircraft). I had seen a few over the years and recall that it had a separate alternator with a higher voltage output, possibly 3-phase. there were voltage warnings on the ones I had seen so assuming that was higher than 48Vrms.

WAI-Wetherill, a supplier of starter and alternator rebuild parts used to have some great technotes on their site. The site recently is pretty impossible to find something. Used to be that you could purchase re-wound stators and specials.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Hey Linnix - Word of advice here. Don't argue with Jim Thompson. He designed automotive regulators for Motorola and knows of what he speaks. Guy's probably got more patents to his name than most of the folks that post here. (me, I have none but do get my hands dirty a lot)

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both have a point, if the load is the battery and you remove it you will get a voltage spike because it takes time to lower the field.

If the load is the headlights and you remove the battery nothing happens because the load is still the same

but once you remove the battery theres nothing to shunt the spike if you shut off the head lights

-Lasse

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Yes, i know at least he listen to reasonings.

In my controlled test environment, the Lexus was started and in low idle (700RPM) with the head lights on. I use it to observe the load before i get to connect the voltmeter. I disconnected the battery briefly to check the alternator and load voltage. The voltage dropped from 12.5V to around 8V to 10V, so i know the alternator is too weak at idle. I reconnected the battery before ramping it up to 1000RPM, the voltage peaks at 14V. I believe the alternator (just purchased) and regulator are good. The car was never gear shifted or moved.

This is nothing compared to what i am doing with my 94 Corolla. The thin metal (not the solid one like others) connectors are broken, My clamp on connectors sometimes get loose. Yes, it did fry the regulator, but at high RPM, i believe. I have been driving with bad regulator for years, no battery explosion and no dead ECU. However, i do have a bank of deep cycle batteries to capture the excess voltage and i discharge them on my drive way lights at home. Currently, i manually switch in the backup batteries, just to see how far i can push it. Eventually, probably an AVR, PIC or ARM controller.

If this kill the Corolla, time for a newer car. I have been waiting for years.