[BC] bulb life
Bob Sutterfield
I have a NiteRider Classic 12V system (now with 14.4V NiMH) with two
MR11C halogen bulbs - 15W spot and 20W flood. I freely switch during
each ride between one bulb, the other, both, or neither, depending
upon the need of the moment. I've been using this system since 1996,
including commuting through El Nino in southern California and through
blizzards in Colorado. I have not yet needed to replace a bulb. I
wore out the switch but no bulb has failed, either when switching or
when just riding along (including adverse conditions of temperature
and moisture). So in only ten seasons I have apparently not yet
reached these bulbs' design lifespan in this application.
With all the accounts and worries of incandescent bulb failures
mentioned here, now I'm starting to wonder: What service life should
I expect from these bulbs? When should I start carrying a spare bulb,
plus tools for roadside replacement?
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Jack Brown.
Bob Sutterfield wrote:
>
> I have a NiteRider Classic 12V system (now with 14.4V NiMH) with two
> MR11C halogen bulbs - 15W spot and 20W flood. I freely switch during
> each ride between one bulb, the other, both, or neither, depending
> upon the need of the moment. I've been using this system since 1996,
> including commuting through El Nino in southern California and through
> blizzards in Colorado. I have not yet needed to replace a bulb. I
> wore out the switch but no bulb has failed, either when switching or
> when just riding along (including adverse conditions of temperature
> and moisture). So in only ten seasons I have apparently not yet
> reached these bulbs' design lifespan in this application.
>
> With all the accounts and worries of incandescent bulb failures
> mentioned here, now I'm starting to wonder: What service life should
> I expect from these bulbs? When should I start carrying a spare bulb,
> plus tools for roadside replacement?
I assume these are dichroic lamps, and Ive just checked the carton of a
Philips masterline ES 20W that I used to use and these are rated for
5000hrs @12V. It has been speculated upon in the past(by Willie I
think)and others, about how much the overvolting will reduce the lamp
life, you'll have to check the archives, or maybe they'll chip in. I may
be mistaken and these may be specialised lamps which are already
overvolted in which case their lives will be much less.
The lives of the dynamo halogen lamps may be rated in hundreds of hrs
but have always dimmed on me after just tens of hours.
Francis Cooke
BS> I have a NiteRider Classic 12V system (now with 14.4V NiMH) with two
BS> MR11C halogen bulbs - 15W spot and 20W flood. I freely switch during
BS> each ride between one bulb, the other, both, or neither, depending
BS> upon the need of the moment ...
BS> ... now I'm starting to wonder: What service life should
BS> I expect from these bulbs?
These MR-11 bulbs have a specified 'life' that is whole magnitudes
greater than an ordinary bike bulb.
Something like 2000h for the MR-11 vs 20h for the cooking bulb.
However that specified life is greatly reduced when the bulb is
over-volted, as they frequently are. It may come down to 200h or
less. That's still a lot of commuting. However these are only
statistical figures - any bulb can fail at any time, so IMO you always
need a spare.
Francis
v garza
I believe the specified life is under ideal conditions. Probably not what is
considered "rugged service" where shock can cause filament breaks sooner.
So, depending on how much shock is transmitted to the bulb on your commutes,
you might experience a failure much before the expected service life. Always
wise to carry spares, as Francis indicates. I believe there are special
bulbs designed for rugged service with extra thick filaments and special
isolating supports in some applications, but don't know if they are
available for bike lights....
Vic
Ian Boehm
> I believe there are special bulbs designed
> for rugged service with extra thick filaments and special
> isolating supports in some applications, but don't know if
> they are available for bike lights....
They might be counter-productive as the mains powered ones I've seen
have lower light output as they appear to operate at a lower
temperature.
Cheers
__o
_`\<,
...(*)/(*)
Ian
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Ian Boehm e-mail: I.B...@bom.gov.au