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Re: Driving lamps, etc.

Subject: Re: Driving lamps, etc.
From: DANMAS <>
Date: Sun, 4 Jan 1998 15:46:07 EST
In a message dated 98-01-04 09:13:23 EST, writes:

> How much additional lighting can be installed before the alternator or
>  generator is unable to supply enough power?


That is a difficult question to answer with any precision, but very easy in
general - not much! If you turn on every electrical load in the car, the
alternator/generator will probably not keep up with the demands as it is.
Luckily, you rarely operate all loads at one time. The horns and the back-up
lights, for example, are only on for short periods of time. When the capacity
of the alternator/generator is exceeded, the battery supplies the extra
current needed. That's OK for short term, but you obviously don't want to draw
from the battery for any extended period, so the total continuous electrical
load at any given time should be little less than the capacity of the
alternator/generator to allow some extra for charging the battery.

To find out precisely how much lighting you can add, total up the current draw
of all devices that you anticipate using at the same time as the lights,
including battery charging current, and subtract that from the capacity of
your alternator/generator. That is the limit of the additional lighting loads
you can add. If you don't drive your car in the winter or in the rain, the
current that was originally allocated to the heater fan motor and the wipers
could be confiscated to operate the new lights. As a matter of fact, you
probably would not want to use driving lights in the rain anyway, because of
the backscatter from the water droplets, so the wipers would not normally be
on when the driving lights are on.

The current capacity of the existing wiring is also supect, so that should be
considered as well.

Dan Masters,
Alcoa, TN

'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
'74 MGBGT---3000mile/year driver, original condition
'68 MGBGT---organ donor for the '74

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