Go Back  Bike Forums > Bike Forums > Electronics, Lighting, & Gadgets
Reload this Page >

LED replacement bulbs in a B&M halogen dynamo light?

Notices
Electronics, Lighting, & Gadgets HRM, GPS, MP3, HID. Whether it's got an acronym or not, here's where you'll find discussions on all sorts of tools, toys and gadgets.

LED replacement bulbs in a B&M halogen dynamo light?

Old 01-21-12, 02:15 PM
  #1  
Senior Member
Thread Starter
 
brianinc-ville's Avatar
 
Join Date: Nov 2006
Location: Greenville, NC
Posts: 1,389
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 100 Post(s)
Liked 57 Times in 40 Posts
LED replacement bulbs in a B&M halogen dynamo light?

Idle speculation:

My wife's Breezer came with a Shimano dynohub and a Busch & Müller Lumotec Oval Plus headlight, which uses a halogen bulb with a standard flanged flashlight base as its main bulb.

I happen to have a couple of LED replacement bulbs around, which I've been using in 3xD-cell Maglites. Just the ordinary mass-market kind from Harbor Freight -- can't remember the make or model. Touted as working with up to 6 D cells.

She's not at all picky about beam shape -- she only rides on well-lit city streets, so this is a be-seen light. Is there any reason not to try the LED replacement bulb (e.g., a chance of burning out the B&M Toplight Plus taillight, or frying the capacitor for the LED standlight in the headlight, etc.)?

Thanks!
brianinc-ville is offline  
Old 01-21-12, 05:15 PM
  #2  
Senior Member
 
minisystem's Avatar
 
Join Date: Dec 2011
Location: Toronto
Posts: 90
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 3 Times in 1 Post
I have a Lumotec N plus, which I believe has the same guts as the Oval plus. I experimented with putting an LED flange bulb in it a few years ago and I can confirm that it works. I ran mine with a bridge rectifier to convert the hub's AC to DC. The LED bulbs have their own driver circuitry in them and I don't know how much it likes to be reverse biased (if at all!), so I think a bridge rectifier is needed. Without one you'll get light half the time when it's switched on, but the other half of the AC cycle, when the polarity is reversed, you won't get anything and there's a good chance you'll fry the bulb's driver.

I can't see any harm coming to a taillight connected to the headlight, especially if it is LED-based with its own standlight. It just takes a portion of the current. If the front bulb failed, I'm pretty sure (but not 100% sure!) that the taillight has a Zener diode or something to protect it from overvoltage.

The Lumotec plus's standlight powers a small LED, so there shouldn't be any issue with a LED replacement bulb interfering with that. It presumably has its own rectifier.

I was disappointed with the light output from the LED bulb, and switched back to halogen.
minisystem is offline  
Old 01-21-12, 11:34 PM
  #3  
Senior Member
Thread Starter
 
brianinc-ville's Avatar
 
Join Date: Nov 2006
Location: Greenville, NC
Posts: 1,389
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 100 Post(s)
Liked 57 Times in 40 Posts
Thanks, minisystem!
brianinc-ville is offline  
Old 02-15-12, 10:21 PM
  #4  
Senior Member
Thread Starter
 
brianinc-ville's Avatar
 
Join Date: Nov 2006
Location: Greenville, NC
Posts: 1,389
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 100 Post(s)
Liked 57 Times in 40 Posts
FWIW, I tried this and it burned out the LED bulb. And the halogen bulb really was brighter, anyway. Fail. Not recommended.
brianinc-ville is offline  
Old 02-16-12, 02:28 PM
  #5  
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,354 Times in 861 Posts
LED's still generate Heat, so they need Heat sinks , buy an LED headlight,
that the Engineers designed to be a as such.

My E-Delux headlight came in yesterday to replace the E6 Halogen ones..

so have 3 halogen headlights to shift, 1 secondary, and 2,
a long and a short lead Primary.
fietsbob is offline  
Old 02-20-12, 09:07 AM
  #6  
Senior Member
 
minisystem's Avatar
 
Join Date: Dec 2011
Location: Toronto
Posts: 90
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 3 Times in 1 Post
I doubt the bulb failed due to overheating. I've experimented with the LED bulb that brianinc-ville was using and its thermal management seems to be adequate - hits about 75°C and reaches steady state, and that's without the benefit of airflow while riding. Well below the typical maximum junction temperature of an LED. The bulb is also designed not to take more current than it can handle.

brianinc-ville, did you run it straight from the dynamo or did you rectify the output first? Un-rectified, I wouldn't be surprised that it got fried from being reverse biased half the time.

I forgot to mention that the main barrier to the upgrade would be the optics. Incandescent bulbs and LEDs need different optics and generally aren't compatible with each other's optics. A LED might throw out more total lumens, but it is not well focused with optics designed for incandescent bulbs.
minisystem is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
tdonline
Bicycle Mechanics
6
07-29-19 12:34 PM
bigbenaugust
Electronics, Lighting, & Gadgets
2
03-21-16 01:06 PM
rhm
Electronics, Lighting, & Gadgets
15
05-15-15 04:04 PM
jimn
Electronics, Lighting, & Gadgets
1
07-09-11 12:20 PM
balindamood
Electronics, Lighting, & Gadgets
4
01-04-10 11:31 AM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.