OT-Automobile alternator rotation direction

And 120RMS has a peak-to-peak of........

339.4 Vpp.

That doesn't matter, because the worst case is about

184 Vp at any given time.

--Winston

Dumb question but as technology advances, is it possible that the PIV of diodes has silently increased while a pn may spec a minimum value?

I don't think any american bearing maker makes a abec 1 class bearing no matter what it is labeled. IIRC, in a seminar I attended, the fafnir rep said, we don't make anything less than Abec 5 no matter how we label it.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Yes.

It's the magic of the 'bin sort'. Others can amplify on this, but no one ever *aimed* to make a 1N4001 diode, for example.

It's just that the sample of diodes from that particular test 'bin' reliably blocked significantly more than 50 V without self destruction and had characteristics that otherwise matched the 1N4001 - 1N4007 series of parts. Had all the sample parts reliably blocked significantly more than 100 V, they *could* have been marked and sold as 1N4002 devices, and so forth.

As you point out, improvements in process consistency mean that the 1N4001 diode you buy today might easily pass all phases of test as 1N4006 device and is only labeled '1N4001' to keep the paperwork simple.

(At my second - favorite tronics supplier, a 1N4001 device or a 1N4006 device will cost you 8.7 cents each in bulk quantities.)

That's how the speed of CPUs, RAMs and other parts are specified, by

*binning*.

Imagine making some fasteners that could reasonably be expected to turn out to be anything from 1/4-20 to 6mm - 0.75 depending on how your lathe was feeling today! :)

matter what it is

anything less

That's reasonable.

--Winston

You run the throttle up slowly until the alternator warning light goes out, then stop.

What positive terminal? We're assuming that its a 120 VAC only unit (or the answer would be trivial).

And there are two diodes in series.

The BATTERY positive.....

ALT+ ------Gen "Neutral" Gen "Hot"----------------------+ BAT term.

I can't picture how putting any voltage on the ALT terminal will do that. It normally has 13.8 from the battery any time.

Plus, as I said, if I was risking what you propose; I'd isolate the system from the car by a) disconnecting the battery terminal and feeding the battery directly. b) Disconnecting the Alt field connections.

I might put one of the headlamps in series with the battery. That gives you a current limit and monitor.

And you sure as heck won't be pumping 115 volts into the battery!!!!!!

So you are saying do the same thing but do it at the easy point - disconnect battery positive instead of alternator output - right???

[ ... ]

I don't know. That could be the case. The main question is "What is the open circuit voltage of the alternator when the regulator is stuck with full power to the field?" It should have that much breakdown voltage at a minimum.

Enjoy, DoN.

Well -- a *peak* voltage of 169.68 V, and add about 15 V to that (the voltage of a somewhat overcharged battery) so you get 184.68 V applied to the diodes (not counting that you have two diodes in series which may or may not divide fairly evenly.) The division of voltage across the diodes does not seem to matter, because one diode is good enough by itself -- unless the newer ones truly have a lower PIV.

After all -- you're not applying the output to a capacitor, but rather to a rather voltage limited battery, so you won't get the full P-P voltage applied to the diodes.

Enjoy, DoN.

Here is the newer rectifiers for alternators.

Yes. That is extra insurance.

The only weakness in Pete and Paul's otherwise brilliant solution is that Clack implied that we cannot change the voltage coming from the generator:

"(...)power from the generator which is making 110 volts AC(...)"

We can wire the 110 V electric drill (humor me) in series with the generator and alternator to act as a power resistor.

Super inefficient but it would get our intrepid builder back to civilization, probably in time for dinner, too. The duct tape would substitute for electrical tape and part of the extension cord would be sacrificed for hookup wire in this emergency situation.

I can safely *assume* that the drill is a 110 V unit because:

1) No mention is made of a charger or spare batteries. 2) The extension cord was mentioned in the same sentence as the electric drill in an associative context.

That's my story and I'm sticking to it.

--Winston

Disconnect BOTH!!!!

(...)

Three phase synchronous rectifier? Very kewl idea!

But,

1) They appear to be using the MOSFET body diodes to do ~ 10% of the rectification rather than using them as voltage clamps (protection devices). This appears odd.

2) Though the MOSFETs *are* bidirectional, they are shown installed 'backwards' from conventional usage. During power production, the drains are negative in relation to the sources. Strange.

3) I didn't see the gate drive circuit for the MOSFETs. I assume it includes a charge pump to keep the high side MOSFETs saturated during peaks.

4) This is a bridge all right but it's really to be used as a source of 3 phase power, not a rectifier. Look at it that way and items 1 and 2 are non - issues because the current would flow in the opposite direction.

--Winston

There is one critical item on the list that was missing above.

Note the radio. VERY possible to pull the radio apart, pull the transformer and rectifier diodes out of it and build a simple trickle charger using the transformer and some wire. The oil could be used to keep the transformer cool while it caries the current.

(...)

The most reliable indicator of genius is the number of plausible alternative approaches one can create. But,

1) The guy was hired to build a cabin. He is not Steve W, (who is universally competent with a claw hammer or electronics, or astronomy or physics or etc. etc.) 2) Tools are limited. He hasn't got needlenose pliers, side cutters, etc. 3) He is tired and hungry after a very full work day. Has he got the patience to make the tools necessary to pull the radio apart? I sure wouldn't have it. Of course, if the radio had an external 12VDC wall wart supply, it's a no-brainer, though it would take a couple hours to charge the battery sufficiently.

I am still in awe of Pete and Paul's idea. With just a pocket knife, the tools mentioned in the Puzzler and say 20 minutes, he could:

Strip out the black wire a couple feet back from the 'outlet' end of his extension cord

Use his socket set to disconnect the battery GND and then the 'Bat' lug on the alternator.

Twist the 'generator' end of one of the black wires around the lug that vacated the 'Bat' connector and insulate with duct tape.

Clamp the 'outlet' end of the other black wire from the extension cord to the 'Bat' lug using it's nut, recently removed.

Temporarily install the battery GND

Plug the drill into the extension cord outlet and plug the extension cord into the generator.

Start the generator and the drill. Run both for a few minutes and try the lights to check state - of - charge.

Shut everything down and disconnect battery GND

Re-install the alternator and battery connections

Start 'er up, put away the toys and drive home

I suspect that the acceptable answer will revolve around using the drill to spin up the alternator enough to charge the battery but I think Pete and Paul's answer is groovy because it doesn't involve taking the V-belt off the truck.

--Winston

What make year and model were the vehicles in question?

I could do that with my 1961 Corvair or my 1945 Signal Corps generator - no clock, no computer, no alarm, no battery drain. A new battery could go six months easy, 1 year with your fingers crossed.

But try that with any car from about 1975 on, and the clock alone is drawing 2 or 3 milliamperes (ma) to run. Add in the memory circuits from the ECU, the radio station memory, and the alarm system, and now you have a 10ma to 15ma draw that will kill the battery over time.

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