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#1130: Tickling the Electrons

Original Air Date: 07.23.2011

   Best Moment

Description: 
This week on Car Talk, are you ready for some wacko theories? Dennis in California puts Tom and Ray to the test, pondering his friend's contention that the best way to charge a dead car battery is by turning on every accessory in sight. Is there anything to this notion of "tickling the electrons"? Elsewhere in Wackyland, Jenny is convinced that her Civic has a harder time starting when its gas tank's not full; Linda needs to retro-fit her ATV to make it a good Summer sled-dog training vehicle; and mechanic-turned-sculptor Coby learns what happens when you add a few extra tons to a half-ton pickup. All this, plus some choice Last Words, and lots more, this week on Car Talk.

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This Week's Puzzler

3rd Open: Mail--The Poem ??Tom Green??s Auto?? and Puzzler Apology 1:50 Find out!

Last Week's Puzzler

2nd Open: Mail. ??Last Words?? 2:15 from 0128. Also used in 0629) Find out!

Show Open Topic

Gas conservation idea - brick in the gas tank.

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WHY IT WORKS :

by Anonymous

Waveaction has it right! P=IxE (Power = Current x Voltage). The Battery will only draw an amount of current proportional to the difference between the charging voltage and the discharged battery voltage, and will absorb the Power at this Current level. As you demand more power from the Alternator (lights, fan, radio), the additional Current demand will cause the Alternator to increase its Output Voltage in order to increase its Current output. This causes the Voltage difference between the battery and Alternator to become greater, which allows more current to flow, and charge the battery slightly faster. At some point of loading (adding the heated seats, rear window defroster, and electric dashboard Hibachi), the Alternator can no longer keep the voltage level up with the massive current draw, and when the system voltage falls below the battery voltage, then the already stressed battery is pressed into service, and supplies current to the system.

Favorite Moment: There must be 50 ways to spell you, Coby . . .

The beauty of alternators is:

by Anonymous

...that the charging current sent to the battery does NOT go through the brushes like it did in the old days of DC generators. ALL of the battery charging current comes from the STATOR (the part that does not turn), and since it is alternating current, it has to go through the diode bridge to get turned to direct current. The brushes of the alternator only carry a small amount of current FROM the battery to create the rotating magnetic field which sweeps over the stator to make the lecktristaddy flow!

Favorite Moment: When Click said the brushes in the alternator carries the electrical current TO the battery. It made me fall off the toilet in amazement as I screamed "NOOOOO!"

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Famous Last Words...

'There's no way this could possibly go wrong.'

The Ford Is My Auto, I Shall Not Want Another

One man's ride is another's affliction.

Novel concept for increasing MPG

Hey, it worked for the toilet!  Let's try it on the car.

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