Disabling the alternator on a car

Awl --

Would seem like a no-brainer, but goddamm, it shore has me beat!

Yeah, I know, pull the fuse!! Yeah, I know, the fuse labeled "alternator"..... :) :)

But when I did that, the alternator light or battery lite would not come on. AND, iirc, I DID check the voltage at the battery, to see if it went down to 12, or was up at the ususal 13-14, and indeed, it stayed at 13-14, indicating a working alternator.

And the engine compartment is so g-d crowded/complicated, I can hardly tell a wire from a hydraulic line, so it's not easy to even find the right wire. I figger at 100 A, the wire would have to be perty thick....

The reason for disconnecting the alternator is this: On an old mazda 929S, the alternator went -- and I could StoG that my mpg jumped by 15%.... would like to re-examine this phenom with my ScanGauge, to see if it is real.

If this is indeed a true phenom, I could wangle myself a bit of a hybrid by just keeping a spare batt in the car, and switch in the alternator when the first batt dies. But basically try to do all the batt. charging at home.

Altho, there proly is no free lunch: I'll proly use my gas savings to buy a new battery every year?? LOL But the actual tradeoff would be inneresting to see.

Reply to
Existential Angst
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15% seems a bit high for a high MPG car, but maybe.

The alternator does take a considerable amount of power to turn.

But I'm afraid that the

Reply to
Richard

Sorry - hit the wrong button.

Without the alternator your battery will not run the car for very long at all. Solid state ignition takes power.

And you will not get much life from the battery either if you pull it much below 50% very often.

What you want is a magneto. :)

Reply to
Richard

We bicyclists agree, assuming that will pretty much f**k up the damned telephone. Hopefully, the driver could start to pay attention, at least to some small degree.

Reply to
AMuzi

BTW, this is the sticker I have on the battery panel of my boat.

It is there so we can tell how much charge remains in the battery. Multiply the percentage by the current rating of the battery to determine remaining amp hours. (Do not use the cold cranking amps rating tho)

Under normal circumstances I never let it go below 60%. I was still using one of the original (20 years old?) AGM group 27 batteries until last year. It would still charge up to 12.45 volts. It didn't get charged for many months during the move, and I have to replace it now.

Another aside, let the battery set without the charger for 24 hours before taking the reading if you want to know the actual battery condition as far as life remaing.

12.60+ 100% green 12.50 90 12.42 80 12.32 70 12.20 60

12.06 50 yellow

11.90 40

11.75 30 red

11.58 20 11.31 10 10.50 0
Reply to
Richard

"Existential Angst" wrote in news:50781447$0$9795$ snipped-for-privacy@cv.net:

You'd be better off to re-examine this with a few months of mileage/fillup recordings, both with the alternator working and with it not (and by that, I mean removal of the drive belt). This sort of statistical analysis is /very much/ dependent on sample size and consistency of data recording, so you need to be very precise.

Your basic thesis is not unreasonable: Honda has, for years now, been regulating its alternator charging using a device known as an Electrical Load Detector. The ELD lessens engine load by reducing alternator output unless there is high demand. However, the ELD is a US-only device, meant to boost Honda's CAFE ratings, not to boost fuel consumption as observed by the owner; its effects are unlikely to include anywhere near a 15% increase in gas mileage.

Have you done the arithmetic?

Suppose you normally get 25mpg; disconnection of the alternator brings you up 15%, or to 28.75mpg. Assuming you drive 12K miles per year, you'd save, assuming $3.75/gal, about $263 per year.

If you mean to run your battery down regularly as you drive (like in the days of the Model-T), then you need a marine/deep-cycle type that will survive repeated dips into low-charge territory. These go from between $140 to $400.

Reply to
Tegger

You would need to disconnect the LITTLE wire drom the alternator, not the big one - and it would throw a code on the engine control computer and possibly put it into a limp mode - not saying it would, but it could. Your alternator takes as much power as the loads connected to it - so fuel pump, ignition, injection, lights and heater fan if used, as well as cooling fan if it is electric. Mabee 600 watts on a cold night, and 50 or 100 on a mild day. Thats less than 1 HP. After starting the alternator needs to recharge the battery as well, so another 1000 watts for a couple of minutes, tapering down to nothing - say another HP for 5 minutes.

If you are going to save 15% on fuel consumption you would have to be able to drive on about 6 HP average without the alternator.

Not going to happen, methinks .

Reply to
clare

Or like on an airplane - TWO magnetos. Then you still need to power the injection - which takes more power than the ignition. And wait - a magneto IS really just an alternator or generator - and it takes power as well.

Reply to
clare

So -- if the alternator has a separate belt, just remove the belt. If it is a serpentine belt, that becomes more difficult. :-)

You might be able to put a mag clutch on it like that on the air conditioning pump -- but the current used by the clutch when it is engaged might negate your savings. :-)

Again -- *if* it has a separate drive belt. Otherwise you disable too much of the rest of the system. :-)

Indeed so.

Unless the alternator is way too powerful for the engine. :-)

[ ... ]

And -- to be complete -- measure the power needed to recharge the batteries at home from the AC line.

Enjoy, DoN.

P.S. I should have set followup-to to the newsgroup in which I read this and responded -- rec.crafts.metalworking -- but I think that the auto tech group really belongs too.

Reply to
DoN. Nichols

At steady-state, middling-speed cruise that's actually plausible. It's when you need to accelerate smartly that you actually use all the horsepower of your engine; at cruise it's only using a very small fraction of available power. Below speeds where aerodynamic drag becomes a significant factor, I would expect power consumption to be in just about that range.

I mean, I can ride a bicycle at 30+ MPH, and I doubt I put out even one horsepower :)

nate

Reply to
Nate Nagel

I built an electric powered Fiat several decades ago. Very light car, with good aerodynamics. 6 HP would move me along at about 9 or 10 MPH. IIRC 10 HP would move me at 30MPH. Accellerating TO 30MPH in any reasonable time took significantly more. Something like 30HP to keep up with normal traffic away from a stop on a slight uphill grade.

Reply to
clare

You don't need to disable an alternator - they can disable themselves! Alternators, at least back in my day, were the least reliable part of any car's electrical systems.

(tongue in cheek!)

Reply to
thekmanrocks

Doesn't seem a likely source of engine drag to me. If you have a 30 amp alternator running flat out and it's putting out full output at

16v(before regulation), that's just over a half horsepower. Even if you've got a horribly inefficient alternator running into a dead short with bad bearings, it's unlikely to absorb more than 1 HP. If you start screwing with running down regular car batteries, you're going to have a lot of grief. There's a minimum voltage needed to just keep today's ECU and injection systems running, factory specs on my VW say 8v and that's 8v under load, not 8v with a VOM with the engine off. My experience with car batteries running down has been mostly bad. After one or two instances of leaving lights on all day, most will short out and won't charge anymore, the plates are thin and warp from the heat of charging.

Stan

Reply to
Stanley Schaefer

Stan's right - a regular car battery won't go a month with abuse like that and it'll crap out on you. You might be able to get it replaced once under warranty, maybe twice - Third time they'll see the pattern and start asking lots of questions.

You MIGHT be able to get 3 or 4 months out of a battery if you use a Deep Cycle rated Trolling Motor/RV battery, but they aren't very good at providing the big bursts of power (200 - 400+ Amps) needed to crank a starter motor over.

Trust me, the 1 - 2 HP that the alternator takes won't make that much difference in the long term.

Believe It Or Don't: Burning the gasoline to spin the alternator directly is actually far more efficient than using Utility Power to charge the battery at home.

Between the thermal losses incurred with a steam or fossil fueled generation system, step-up and step-down transformers and transmission line losses, you lose almost half the energy you started with through making the electricity and getting it from the power plant to your house.

Hydroelectric, Wind, Solar is a lot more efficient to make the power, true - but then they roll the cost of building and maintaining the powerplant (and the dam) into the power rates - and they aren't cheap.

Oh, and you want to kill the alternator, you have to pull the control wires - AND the Battery lead. Yes, there are some models that don't need any external excitement at all - If it's spinning and the big Output wire is connected to the battery, it's putting out ~13.8 Volts.

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Reply to
Bruce L. Bergman (munged human readable)

This all reminds me of the paraphrased Laws of Thermo:

  1. You can't win
  2. You can't break even
  3. You can't even get out of the game.
Reply to
Existential Angst

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