Page 2 of 2 FirstFirst 1 2
Results 16 to 18 of 18

Thread: Honey I shrunk the alternator

  1. #16
    rabid reader dbrick's Avatar
    Join Date
    Apr 2003
    Location
    Santa Cruz CA
    Posts
    1,739
    Quote Originally Posted by wbrownell9 View Post
    From another thread...
    That's interesting. Where's the other thread?
    David Brick
    Santa Cruz CA
    2007 R1200R

  2. #17
    Still plays with trains. tinytrains's Avatar
    Join Date
    Oct 2009
    Location
    Torrance CA
    Posts
    492
    Quote Originally Posted by wbrownell9 View Post
    From another thread I noted that BMW is instituting some power-saving measures. Voltage to the high beams goes from 0 to 12V then back to zero, so there's about 10 milliseconds of full power then 10 milliseconds of nothing, etc. The filament doesn't have cool down enough to decrease its brightness, and it's too fast to flicker. But the result is that the average power consumption of the 2 55W high beam bulbs is decreased from 110W to 55W. Dash has low power needs, either LED or something like a cellphone display. LED corona, tail and fog lights require maybe 20% of the power of equivalent incandescent bulbs. Brake and turn signals aren't generally on all the time so they're not a constant drain, only intermittent, and they're LED too. ABS only needs power when it's actually working. OTOH all the computing power on the CANBUS probably likes juice. ISTR that I heard to allow 300W for the onboard electronics.

    Even with all-incandescent bulbs I could never figure why my Goldwing needed a 1200W alternator. Maybe so I could do some roadside arc welding?
    Pulsing the power to LEDs is a very common trick in the display and lighting business for decades. This is the first time I have heard of it on head lights. The human eye latches on the peak light and does not notice the off time if it is fast enough. As a result, a 50% duty cycle light can look twice as bright as 100% one, on the same power, or just as bright on half the power.
    1988 K75 Low Seat
    2009 R1200R Roadster

  3. #18
    Registered User wbrownell9's Avatar
    Join Date
    Jun 2013
    Location
    New Castle, DE
    Posts
    50
    Quote Originally Posted by dbrick View Post
    That's interesting. Where's the other thread?
    It was in connection with a thread about why the Flash To Pass often only needs to be triggered once to open the garage door instead of twice like it says in the directions:

    http://www.k1600forum.com/forum/bmw-...html#post30360

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •