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Old 01-08-2017, 10:23 AM   #1
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ATTENTION EOC DRIVERS: How to trick alternator into charging

Last year, I mentioned a problem with keeping my battery charged, because aggressive EOC (engine off coasting) gives the alternator so little running time to recharge the battery.

I noticed an interesting phenomena, which may help other EOCers.

When idling at a stoplight, turning on/off the cabin heater fan tricks the charging circuitry into charging the battery.

But when I accelerate from the dead stop, the charging circuitry will notice it has been tricked and will then stop charging.

If you hold your speed constant on the freeway, this trick works, too, but the drag of the alternator charging will, of course, degrade your MPG.

UPSHOT: If you're gonna idle for minutes at an intersection you might as well use that time to recharge your battery by simply turning your heater fan on/off. Turning on/off headlights will do the same, BTW.
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Old 01-08-2017, 11:01 AM   #2
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The alternator monitors the battery voltage at all times and tries to maintain it at about 14.2 volts (Jap cars a little higher as well as U.S. ). If you have worn brushes or a dirty slip-ring it makes it harder to regulate the voltage. Putting a load on/off the electrical system may help a bad alternator start charging because of a major change in voltage

Have your charging system checked out for both voltage and amperage. Also have a load test done on your battery as repeated cycling can cause sulfation

Oh am/was an industrial electrician for the past 50 + years.
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Old 01-08-2017, 05:10 PM   #3
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The alternator monitors the battery voltage at all times and tries to maintain it at about 14.2 volts (Jap cars a little higher as well as U.S. ). If you have worn brushes or a dirty slip-ring it makes it harder to regulate the voltage. Putting a load on/off the electrical system may help a bad alternator start charging because of a major change in voltage

Have your charging system checked out for both voltage and amperage. Also have a load test done on your battery as repeated cycling can cause sulfation

Oh am/was an industrial electrician for the past 50 + years.
BlueRover, is a "slip-ring" another term for for "pulley"?
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Old 01-08-2017, 05:26 PM   #4
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BlueRover, is a "slip-ring" another term for for "pulley"?
No on a DC generator there is a commutator consisting of several copper segments connected to winding in the rotor (rotating part) and the current flows from the rotor.

On an alternator there are two copper bands at the end of the rotor but the control voltage is fed into the rotor. Very little current so that is why dirty brushes can cause problems.

Current is generated in the non movable part (stator) as AC and then fed through diodes to produce DC current. Most cars have an assembly that contains both new brushes and new diodes.

For a more detailed

Alternator Components - How Alternators Work | HowStuffWorks
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Old 01-08-2017, 05:31 PM   #5
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Ah. Thanks for your electrifying explanation, BlueRover.

In 50+ years, ever see anyone get the shock of their life?
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Old 01-08-2017, 05:53 PM   #6
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Ah. Thanks for your electrifying explanation, BlueRover.

In 50+ years, ever see anyone get the shock of their life?
Yes ! One time one of my co workers touched a 600 volt main feed and flew back about 15 feet and stopped moving. I immediately called for first aid and kneeled down beside him and there was no breathing. Made sure his air ways where clear and just as I started to give mouth to mouth, his eyes opened wide and he said "what the F%$# are you doing". After what seemed like minutes the crowd that had formed around us broke into laughter, more relief than anything.

I did get free coffee for a few days LOL
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Old 01-08-2017, 06:30 PM   #7
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WOW!

I forget. Is it the amps or voltage that'll kill ya?
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Old 01-08-2017, 07:14 PM   #8
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Amps as low as .075 can kill
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Old 01-08-2017, 07:47 PM   #9
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Amps as low as .075 can kill
WOW! Isn't that 75 milliamps? The worse cellphone charger is 500 milliamps.

What conditions would need to be met to get oneself killed with a phone charger, BlueRover?
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