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Popping Diodes

MikeH on Thu June 14, 2007 10:10 AM User is offline

I just quit a DirecTV Sat. installers job to take a consulting position back in the profession I really care about - mainframe computer programming and project management. Have to travel some but oh the $$$.

Anyway, during my last week the transportation mgr really came down on the techs about leaving anything plugged into the cigarrette lighter socket when the van, a brand new Ford E250, was not running. His directive stated that the load would pop the alternater diodes. Now, being the astute tech that I was, I ignored him. At any one time I had my GPS, Sat meter and Ryobi 18V bat charger going - all at the same time.

Nick, you seem to be the electronic genius on this forum, so, please enlighten me. Everything I researched said that the mgr was wrong and that he is talking about old technology. True or not true?

Later,
Mike H.

NickD on Thu June 14, 2007 11:32 AM User is offline

May discharge the battery a tad, but all this electronic crap they are putting into vehicles today does the same thing, with or without anything plugged into the cigar lighter.

Alternator diodes only conduct when the stator voltage is greater than the battery voltage, and the vehicle has to be running before that happens. With the engine off, all six diodes are reversed biased, but even a direct short on the alternator output while it's running at full speed is not suppose to pop diodes, the stator/field combination is current limited.

What's with supervisors, my friend that spent his whole life working for the FAA never got promoted, that is because he knows his stuff, the FAA and the government outfit I had worked for only promotes the idiots to supervisor positions, because they can't do anything else. Was your supervisor also promoted because he is also an idiot? Sure sounds like one.

MikeH on Thu June 14, 2007 6:14 PM User is offline

Yeah, the guy was promoted instead of being fired. He is/was an in-your-face kind of guy, you know, the kind that starts off a sentence with " I know you are a smart guy". YOu know he does not really mean it.

NickD on Thu June 14, 2007 7:39 PM User is offline

Don't I know the type? Just got a new FAA inspector that thinks he's god almighty, I refused to do another inspection with him, e-mailing both his bosses. Every inspector before him was wonderful, co-operative and helpful, this guy is a psycho. I don't need that at my age, real easy to shoot down as well, good thing he has a clear plastic stomach, so he can see where he is going due to the unique position of his head.

bohica2xo on Thu June 14, 2007 8:31 PM User is offline

Nick:

That is the "Belly Button Window" to be used as an aid to navigation...

Other managment types are required to wear a necktie - this prevents the foreskin from slipping above their collar, and obscuring their vision.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Fri June 15, 2007 6:19 AM User is offline

The tides sure turned when the CO of the Great Lakes Naval Training Center Electronic School came to me for an interview for a civilian job. Was fair and unbiased, but had to say, I am sorry, you just do not meet our job qualifications. And he didn't, we were looking for a guy that was very good at converting vacuum tube circuits to solid state, not a guy that was great at making life miserable with chicken chit military discipline. And serving under him, he was very good at that. Quite a different fellow when applying for a job, couldn't tell me to stand at attention while he was chewing my butt off.


boatmoter on Thu July 05, 2007 7:06 PM User is offline

the items you stated plugged into the lighter would not draw anymore then 1 to 1.5 amps..its enough to draw the battery down after about say.. overnight.. as long as the battery is strong enough to start the engine,then the alternator is capable of charging the battery back up with out damaging the alternator..
when you get into a 400 watt usage on the vehicle than your going to start having alternator problems..

and the normal acceptable drain for a vehicle is 0.5 amp... half an amp..

-------------------------
Glenn //

NickD on Sun July 08, 2007 9:28 AM User is offline

" and the normal acceptable drain for a vehicle is 0.5 amp... half an amp.. "

Believe you meant to say 0.05 amperes maximum, but that is being cut back to 0.02 amperes, that is 1/50th of an amp.

boatmoter on Wed July 11, 2007 8:55 PM User is offline

I was taught 1/2 amp or less.in class room testing for ford. of course thats after the modules are discharged.

-------------------------
Glenn //

NickD on Thu July 12, 2007 8:24 AM User is offline

Less than 1/2 ampere is correct, but a half ampere of standby current draw would leave a standard size battery cold dead after four days of sitting. Not very convenient if you leave your vehicle at an airport for five days. The always hot electronic modules, RAM memory, anti-thief devices, well they work as the thief is trying to swipe a vehicle that he can't start with a dead battery all contribute to high standby current drain. Do we really need a dome light that stays on for 30 seconds after we lock our vehicles? A vehicle like my DeVille draws 20 amperes of interior light current that no one is using and if the Power MOSFET doesn't switch off, the battery will be stone dead in about four hours. Ha, already happened.

Alternators did use the diode trio that only provided field current when the alternator is spinning, that is history, way too expensive, now one transistor where moisture in the alternator can switch on the field in a parked vehicle putting an eight ampere load on the battery, have to keep the stockholders happy. A vehicle like the Model A Ford would draw a flat zero from the battery so can sit for a long time and still start. Modification to new systems is near impossible unless you have access to the source code to change the BCM program. Way too much work, just got a AAA card instead and use it.

Dougflas on Fri July 13, 2007 6:46 PM User is offline

Where you may have a problem is where you discharge the battery so the alternator has to continuously put out full output to charge the battery. That is why when you change an alternator, they advise you to charge the battery externally first. This is where some repair shops always wanted to sell you a new battery along with the new alternator.

NickD on Sat July 14, 2007 7:04 AM User is offline

Denso's don't have this problem, neither to earlier Fords, the 4G series has weak diodes, the Delco CS-144 series does not have this problem, but the really main culprit is the Delco CS-130 and more particular in FWD vehicles with poor alternator cooling and the added burden of electric fans. It also has three strikes against it, many units came with a reversed pitched rear fan that fights the front fan drastically reducing diode cooling, the OE diodes in a 100 ampere alternator are only rated at 75 amps, and chip diodes were used mounted on an unplated copper heat sink that would corrode under the diode increasing resistance and heat. Heat is the major enemy.

All of these problems were cured in good aftermarket rebuilts using a higher pitch rear fan of the correct direction and hermetically sealed pressed-in diodes with a 150 amp rating.

If a shop told me I needed a new battery and it must be fully charged first, would start walking as many rebuilts are just using old sand blasted OE or even poor grade aftermarket parts. And what happens if your vehicle sits for a week or two, you get in a hurry, start it, switch on the AC, and hit the gas turning over 3,000 rpm on the engine? Pop goes the diodes. These poor alternators will survive if you just start the engine and let it idle for about 20 minutes to initially recharge the battery. There are good rebuilts on the market that solved these problems, but just like anything else, have to be able to separate the BS from the facts.

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