Can somebody please explain why..........

......... the instructions for my Lightforce handheld spotlight states: "Shortening cable length can be responsible for VASTLY shortening globe life"? How would shortening the power lead do this? The globe is referred to as an "Xenophot" globe, if that makes a difference. Thanks for any advice.

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They must have taken the lead resistance into consideration when choosing lamp voltage and must think that a short lead will increase voltage to the lamp excessively ???

Reply to
F Murtz

Seems strange in that case as car battery voltages vary considerably from fully charged (13.8v) to less. If the spotlight is a 100W than the current drawn from a 12v supply will be approx 8.3A, obviously more if the voltage is a bit higher.

8A continuous current drain needs a lead with a low resistance. I can't see shortening the lead being an issue. ???
Reply to
Alan Rutlidge

The length of the lead forms part of the total circuit resistance and plays a part in limiting the inrush current at turn on. The lamp resistance is VERY low when cold so the lead limits that first rush of current to a level the designer thought was OK.

John G.

Reply to
John G.


** By increasing the voltage getting to the lamp - silly.

Incandescent lamp life is very strongly affected by voltage - eg increasing the voltage by 10 % above nominal reduces the expected life by a factor of 3.

To a good approximation, lamp life is inversely proportional to the 12th power of the operating voltage - provided that voltage is not more than say

25 % above the nominal rating.

..... Phil

Reply to
Phil Allison

Is it a cheap chinese / taiwanese product where the power lead consists of a few fine strands of black scale covered copper wire?

Reply to
K Ludger

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