Re: (ET) Batteries and lighting

[makinglightning comcast net]

I talked to a friend of mine that is familiar with incandescent bulbs and he was also sayying that the lifespan will decrease logirithmically as you raise above the rated voltage.

He also mentioned that when you reduce the voltage by not much, the light output drops off dramatically.

Things are all worse the quartz halogen bulbs, which is the version of landing lamp that I intend on using.

It really sounds like I should use a switching supply, which will be impossible to find, or design one, and I do not have the time for that. So it looks like I will be wasting a little power and putting a resistor in series.

I might sacrifice a bulb to see for myself how badly it kills the lifespan.

 

I work for an automotive supplier here in Deetroit and the 42v stuff is just about dead from what I hear.

 

Kevin

> -------------- Original message -------------- 
>
> > - Greetings - 
> > 
> > The question recently developed about the lifetime of incandescent bulbs 
> > running on voltages other than the rated voltage. Many moons ago in a 
> > lecture I learned that bulb life varies approximately according to the 
> > following formula 
> > 
> > (actual life/nominal life) = (nominal voltage/actual voltage)^11 
> > 
> > That is, voltage ratio raised to the 11th power. The lecturer suggested 
> > that a 230 V bulb rated for a thousand or so hours would last about 3000 
> > years running on 115 V. 
> > 
> > If the auto induestry starts producing cars with 42 V systmes (with engine 
> > running) the actual on-board battery voltage, fully charged, will be the 
> > same as many of our tractors, about 39.6 V. Sounds like a ready supply 
> > of bulbs at a very useful voltage. 
> > 
> > Incidentally, since a bulb burns more brightly with increasing voltage, 
> > and since tungsten has a very large coefficient of resistance as a function 
> > of temperature, increasing the voltage on a 12 V headlamp from 8 V to 11 V 
> > to 14 V results in a very small increase in current. Because of this, I 
> > find a headlamp quite useful as a load for testing the lifetime of a lead- 
> > acid battery (Peukert curve). Just read the voltage every so often and note 
> > that the current has remained almost constant. 
> > 
> > Keep on Elec-Traking. 
> > Rhett George 
> > 
> > _______________________________________________ 
> > Elec-trak mailing list 
> > Elec-trak cosmos phy tufts edu 
> > https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak