What wattage headlight to use?

[Earthman]

Does anyone have any thoughts on what minimum wattage bulb would be appropriate to allow reasonable safety on a MB while going 20 MPH on a dark street?

I’m building a 12v electrical system for my MB and I’m trying to figure out what size bulb (in Watts) to use for the headlight. This seems to be the hardest part to work out ‘cause there’s lots of trade offs with respect to brightness, weight of battery, life of battery, the reflector used, etc.

I'll probably end up building the headlight since I haven't found anything commercially made that will meet my needs. I’ve got most other things figured out. For example, I want to use a 2 A-hr gel cell battery max to save weight. I only need about an hour of ride time, which puts me in the 10 to 20 Watt range for the bulb, but I have no idea what can I get away with.

I'd appreciate hearing from anyone who has been down this road before.

Thanks

[Cabinfever1977]

i have a 18v cordless tool battery with 1hr charger $45
2 12v car clearance lights 1 clear and 1 red hooked up in serial to = 24v
a inline fuse and a toggle switch $4
battery will keep lights bright for many many hours/days
extra batteries are only $20 and are sold at walmart or cordless tool places

im guessing the lights are 10-12watts? for clear front
and 5-10watts? for the red rear light

i have a clear light with dual bulbs in front$3-5 and a red dome light in rear$5-6.
you can buy the lights at any car place.
my lights can be seen atleast 1,000ft+ or more down the road

[Outrunner]

Cabin,
I have recently installed a 12volt system on my bike, and after many hours of searching for the right headlight, I ended up at WalMarts and
bought a tractor headlamp for $11.95. It's really bright and has a rectangular shape with a tough plastic housing. The lamp does draw
about 35-40 watts, so I made a battery box from a aluminum box
sold at Fry's or R-Shack. I used a 4.5 amp 12volt battery and so far it
has lasted 1hour and 42 minutes before It had to be recharged.It's
great and VERY bright. I just hook it up to my trickle charger in the
evening and she's ready to go!

[Cabinfever1977]

thats very cool,you know if you want it to last longer you can use a dimmer switch which you could adjust the brightness.

[ZnsaneRyder]

If you want really long battery life, you can use LED lighting. I get over 8 hours from 18-LED light on a 12V 4AH NiCd battery pack.

I also have a high-power 3W 12V LED and also a 55W 12V Halogen light. I get about 7 hours with the 3W, but only 40 mins with the 55W, so I use it sparingly, and stick with LED for long rides.

It's nice to use the bright light when you need it, but having a low power light for most of the time will save batteries. Also if your batteries get low, the lesser power light will still be able to run for a bit longer for emergency.

In your situation with only a small 2AH battery, LED is a must. You can have just 1W-3W of LED power and have plenty of light for hours. Regular bulbs, even a small one will drain your battery too quickly, and you would be lucky to get a full hour.

[Earthman]

Thanks for all the feedback. For experimenting with different wattage bulbs, I’ve built a headlight out of a 4” dia., Schedule 20 PVC cap, some scrap aluminum, and a 12VDC, 11 Watt landscaping flood light (photos attached). I like the look of a larger headlight – I think other motorists will see it better as well.

The flood light I’m experimenting with now makes a rectangular beam that is about 20 deg. wide by 3 deg. high (see photos). I don’t know if its brightness is adequate for night driving because it’s raining here and I haven’t been able to go for a ride to test it. But, I like the pattern of light it projects.

As far as batteries go, I’ve just about given up on using a lead-acid gel cell and will probably end up using nickel metal hydride batteries. This is because of the following:

Lead-Acid Batteries:
1. Relatively inexpensive, but heavy (so am I, so I want to keep the weight down).
2. Their discharge curve is such that the voltage keeps dropping with time, so the headlight will dim as well. This is annoying.
3. They don’t self-discharge as readily as other types of batteries, so chances are the battery will not be dead when I need to use it. I don’t plan to ride at night very often.
4. Discharging lead-acid batteries below about 10.5 volts is bad for them – it decreases their service life.

Nickel Metal Hydride Batteries:
1. They’re relatively expensive, but much lighter than lead-acid. Also, if properly maintained, they may be less expensive than lead-acid over the long run.
2. Like nickel cadmium batteries, their discharge curve is relatively flat until just moments before they die. In other words, their voltage is nearly constant until they die quickly with little notice.
3. I can have a battery pack made to just about any voltage in steps of 1.2 volts. If I what to “overdrive” the bulb for additional brightness, but shorter life, I may be able to do it as long as I can make or buy a proper charger for the battery.

Right now, I’m thinking of carrying two nickel metal hydride battery packs of about 4 A-hr each. That way, if one dies, I’ll be able to swap in a fresh battery pack. This way the “die with little warning syndrome” won’t be as much of a problem.

Anyway, that’s where I am today. I may change my mind again after I tinker some more with my new headlight.

[huckersteve]

Good looking light! A little big for me personally but really well done man, nice work.

[Outrunner]

Wow! That's a very innovative headlight for sure. I like the custom
made adjustment screw on the bottom too. Great job, I agree with you
about being seen by 4 wheelers for safety. Now you need to consider
putting a front drum or disc brake setup on it.

[Dan]

Really cool EM!

[eDJ]

Is this light going to use a fresnel lense ? I mean a lense like a sealedbeam headlamp
on a car or motorcycle or will it be like a flashlight with a clear glass lense.

The light I'm working on will probably work more like a spotlight than a controlled
lumination light as it will just have a glass disk for a lense. I've been looking for
a small motorcycle or motorscooter headlight lense about 3 inches in diameter
to mount ahead of my bulb. It will make some difference when it goes thru that
fresnel.

When you look at all the little lines in a headlight lense and wonder what or why they
are there, these are like small magnifying glasses that direct the beam and intensity
of it. If the lamp has a hi or lo setting it will change the lighting dispersement. You can
measure the light on a wall with a meter to determine the lumens that fall on a graph
if you can find a large white wall. (the yellow shows the approximate single power headlamp
pattern) The high low beam of auto headlamps or motorcycles may be 45/55 watts
but in this case the lamp may be significantly less.

But if you're only using the one intensity of bulb the curve of the reflector and fresnel lense
will determine the dispersement over the path in front of you. The graph below shows
how this stuff is measured. The power of the single bulb may determine whether your lamp
is seen as high or low beam. If you are riding less than 30 mph you really won't need
a hi beam.