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Re: MG TD Voltage Regulator Cooking Battery?

To: BobMGT@aol.com
Subject: Re: MG TD Voltage Regulator Cooking Battery?
From: Barney Gaylord <barneymg@ntsource.com>
Date: Thu, 29 Jun 2000 02:27:28 -0500
At 01:19 AM 6/29/2000 EDT, Bob Donahue <BobMGT@aol.com> wrote:
>The ammeter in my TD has always read around plus 15 amps at crusing speed.
.... I hooked up a voltmeter and discovered the generator was pumping up
the battery to 16 volts. .... the shop manual indicates the correct setting
is 15.8 to 16.4 volts at room temperature. The rule of thumb in EE circles
is 14 volts for charging a car battery. ....

The voltage reading specified in the shop manual is to be measured directly
on the output terminal of the generator.  With resistance in the wires, and
the length of the conductors involved, and resistance in the battery (among
other things), this may equate to about 14 volts when measured directly on
the battery terminals.  In other words you have 14 volts drop across the
battery and 2 volts drop in the rest of the circuit.  If you are seeing 16
volts at the battery your car is indeed overcharging, and you are at
considerable risk of burning out the generator as well as cooking the
battery.  Time to detune the regulator a bit.

Barney Gaylord
1958 MGA with an attitude
    http://www.ntsource.com/~barneymg


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