But dosnt that mean your still only getting 2.7 Ah???

Its cheaper to get a lead batt, and 2.7Ah would be a prety small lead batt, not too heavy, and cheap.

I just bought a 20w MR16 spot (12deg), 2eu. and a button switch. Im still looking for housing, im thinking a plastic cup. i found a cheap 17$ charger, and the bat is going to cost about 13$ (lead 4.5Ah) but its close to 2 kgs i think...

OH and i had a extremly hard time soldering to the MR16's leads, it was horrible, i used sand paper and lemon and it barley stuck... and i cant find flux!... lemon works...

you should have gotten yourself a couple of those ceramic mr16 sockets. they make a big difference, as you dont have to worry about the soldering problem.

SLA smart chargers are cheap--plug and forget. That is why I like them--I just leave the batteries plugged in until I need them. Also, SLA hold their charge much better than other batteries; they can hold their charge for months with very little loss. Lead acid batteries are a fairly mature technology and are used in medical equipment, solar power, emergency lights, etc. Here are some links I have collected:

SLA battery mini tutorial according to me

http://nordicgroup.us/s78/batteries.html

Ok, I have assembled my lights and tested them. My switch screws into the back of the light housing and the rubber cap screws into the top of that switch from the outside which is a sweet setup. the one thought going through my mind now is the battery. Should I solder a line directly to the SLA? or should I just wire it and shrink wrap those wires? Also, Im assuming I should, after soldering in the fuse, put in some sort main unit that can have multiple wires coming off of it so I can run both lights, the strobe, and the led/reflectors I have, directly off of that unit. I have seen plastic ones in electrical departments where you can screw in the lines to it. How do those sound? should I consider soldering in the lines in some manner or just use the screws that are there?

I do have a 3 way switch that im considering hooking to my main light, but that would mean more wires in one housing.

A quick peek at my geek project.

1) Three pieces of PVC pipe fitting, 1 1/2" diameter.
2) Beveled inside on the front edge on the first piece - to accomodate the lip on the MR16 bulb. I used a grinding bit on my dremel tool, and some mineral oil dripped on the surface to prevent it from totally melting the PVC from friction.
3) The back piece (pipe cap) gets two holes drilled into it and mounted where the front reflector used to be.
4) Silicon sealant (goes on white, dries clear) glues the MR16 into place and seals the front piece from water. Replacing the bulb will involve cutting the old one out with a razor and cleaning the sealant from the plastic - it'll take the new sealant longer to dry than to change the bulb.
5) The fully assembled and attached light. The middle segment has a hole for the wire to come out at the bottom, which is fed through after screwing it into the front piece. The whole assembly is pushed into the already mounted pipe-cap... It's tight enough to not need any further attachment, however it would be easy to include a short-screw through to hold in place if this was not the case or one was worried that it might pop out. I put Park Tools waterproof grease on the threads and the edge of the light that meets with the cap so that I'll be able to remove it later and to guarantee the seal.
6) Last shot (out of order) shows the MR16 in the beveled PVC piece, with fresh sealant.

No pictures of the light actually functioning yet, as I've not completed the electronics housing which is the white box hanging under the seat-stays. That'll be hopefully completed in November when I can afford the batteries and charger.

The light itself cost around $15 all said and done, for the PVC piping, 20 watt bulb, and silicon sealant. Nuts, bolts, wiring and reflector mount I already had, and the electronics housing is an old plastic box from a camping first-aid kit. It latches from the bottom (as mounted) which will allow it to swing open in the triangle to access the batteries without removing the box.

I just got a MR16 12 Volt Super High Powered 3 Watt Luxeon LED ($15.99) from Autolumination.com. I just gave it a quick test last night and it was impressive. The center spot is not quite as bright as my 20 watt halogen, but the light-bleed to the side is brighter and more even. I think this might do the job for a in-town headlight. I'll try to get it installed tonight and get a report this weekend--our forecast for tomorrow is for ~2 inches of rain. :eek:

I found a 12v MR16 20 led light, 1.8w... for i think 9-12$...
I was thinking tail light, just gota figur how to get it red...

Buy one with red LED's. It's much more efficient. Red LED's only produce red light, so all of the energy goes to producing light. If you put a red lens in front of a white light, it filters out everything but the red portion of the white light. All of the energy used to produce the non-red portion is wasted. This is particularly problematic with white LED's, which produce relatively little red light -- their light is noticeably bluer and whiter than incandescant.

Here's a link to a red LED MR16 for less than $8: http://store.peclamp.com/led001.html

Do you by any chance know if either of the autoumination MR16 3W Luxeon LED bulbs (normal and wide angle) will fit into the Optronics driving headlights housing (like, QH-8CC or something)?

I recently bought a 21-led MR-16 bulb on Ebay for 8.49 including shipping, and I have to agree with your general assessment. It's a very good "to-be-seen" light, visible and prominent from quite a distance, but it doesn't do much to illuminate the path in front of me. As a test this week, I've replaced my old setup of dual 10w halogens with one 20w halogen and the LED. I figure it's about the same power consumption and a lot more light.

It does suffer from the same misleading advertising that haunts almost all LED bulbs.
A 10 watt halogen produces somewhere between 120 and 400 lumens, depending on the manufacturer. So it's not even close. Interestingly, the lumens per watt are about the same with the LED and the halogen; the quality of the light differs.

My feeling is that using halogen and LED's together gives the best of both worlds.

Hey folks: This is the best thread on BF.net My Question for the masses:
What happens to an SLA if it stays out overnight during winter? I have to leave a bike at the train station everyday and hope to charge it when I get to work in the morning. After charge I will ride to the train(30min), park it in a bike box, ride to work (30min) in the AM. The SLA is 12V 7amphr, currently lights a 50W H3 halogen which gets about 1.25 hrs burn time. Any guesses if I will be able to make the 2 30min commutes? I will change batteries at work with a completley charged SLA each day. On Monday the battery will have been left over the weekend.
Thanks all. Charlie

You may see a reduced run time (lower amp-hours), because the cells are cold. I'd also switch that 50W bulb for a 35W high-efficiency bulb.

Thanks. I will but have to make the holder. My current light is sealed and the wrong shape. I have scheduled time this weekend to make a few as I have 2 bikes to outfit.

I sure hope so, because that is what I have. I'll report back after I get it in.

If it is fully charged it shouldn't make too much of a difference. I park my bikes outside on a carport and haven't noticed a difference (lowest temp around 18 degree F.). I agree that you should get a lower-watt light. I used a 7Ahr SLA two years ago with a 25 watt sealed beam LV505 (Home Depot) and got way over two hours run time.

Map_Tester, I could be wrong, but I think I remember someone in one of these threads reporting that those LED MR16s won't properly fit in the Optronics housing, you might want to look into that, but I guess since they're on the way already you can probably find some solution that will work.

hey, im wondering about LEDs and resistors. I have 2 volt LEDs and am going to run them in groups of 6 for 12 volts, but I am concerned about the upper end of the voltage spectrum for my batteries. 12 volt sealed lead acid battery can have up to what starting voltage? just wondering to know if I will need resistors to keep the life of my leds long, or at all.

http://www.members.optusnet.com.au/r...DIY_Lights.htm


http://www.bike-recumbent.com/headlight.shtml


http://www.instructables.com/id/E3BGQT6Y7PEP286N6P/


I'm fed up with looking for a light that is good and sub 50 dollars - probably b/c there aren't any.

So I'm going to try and make my own in the next few weeks with a 20 or 35 watt MR15 halogen from http://www.peclamp.com/buymr16color.html

and I'm going to try and get a cool look with some baked bean cans as housing :)

Next - off to a Batteries Plus store to find a battery! woot!

Up to 13.5-14V.

I think you should try to preserve the tin-can look by carefully removing the wrapper, then re-gluing it with strong glue. Then coat it with several layers of laquer to keep it looking good, and to prevent the can from rusting.

:D

Well NeezyDeezy, you were right about the size. I was able to fit it into the Optronic housing by drilling a small hole through the small overlap between the front and back of the housing. The LED light does not throw as strong a beam as the halogen, but works great as a to-be-seen light. I think I can now experiment with smaller/lighter batteries.:D Also, you can see how I mount the light by using a Minoura Bottle Cage Holder, and sawing off the 'wings' that the water bottle screws into.

I moved my batteries from the rear rack to one of the water bottle cages. Having the batteries mounted on the rack made the bike "back-heavy" and ackward when carrying it up and down the stairs at work.
For now I have the batteries secured in a tennis ball can in the bottle cage. No pictures yet. The tennis ball can is the same diameter as a water bottle and is waterproof.

http://home.mindspring.com/~rhorne/G...ight%20015.jpg

Does anyone know of a "straight" (no narrow neck) water bottle or similar waterproof container that I could use instead of the tennis ball can?

I'm running a MR16 LED in the optronics housing. The crucial dimension is the depth of the bulb, the connector is right up against the back of the housing. It looks like Map Tester's bulb is a little deeper than normal. If the bulb protrudes in the front it's not a problem as the housing is open on the front.

shoot- i'm waiting on a 3X3W cree Led mr16, and was planning on running it in the optronics housing.

The problem is that the bulb is too long, and thus not enough overlap for the threads on the faceplate?

LED's are funny creatures. They don't operate as a fixed resistance the way that light bulbs do, they're more like on-off switches. The voltage rating on a LED is the "forward voltage." If the voltage applied is greater than the forward voltage, the LED turns on. If the LED is on in a circuit with no resistance, you have a short circuit, and something will burn up.

What you need to include is a "current-limiting" resistor, which goes in series with the LED to limit current in the circuit. To size the resistor, you need to know three things: the forward voltage of the LED, the maximum supply voltage, and the maximum current the LED can take. As an example, assume you have a 12 volt nominal SLA battery that produces 14 volts at full charge, and six LED's with a forward voltage of 2V and a maximum current of 100 mA. The LED's will always drop their forward voltage, so 12V will drop over the LED's, and the remaining 2V will drop over the resistor. The current through the resistor is the same as through the LED's, so it can be no more than 100 mA. Using Ohm's Law to solve for 2V @ 100mA gives a resistance of 20 ohms. To buy a resistor you need to know its resistance, and also its power, so solving Watt's Law for 2V and 20 ohms gives .20 watts.

With a current limiting resistor, there is always some efficiency loss. The efficiency is given by (forward voltage)/(supply voltage). Note that the value of the resistor does not affect the efficiency.

As the supply voltage drops, the efficiency increases, but the power output decreases. The power output is given by (Power at maximum voltage)*(Supply voltage-Forward voltage)/(Maximum voltage-forward voltage). Note that when the supply voltage reaches the forward voltage -- 12 V in our example -- the power drops to zero and the LED shuts off. Again, the value of the resistor does not affect this equation.

So when you are designing your circuit, what is important is the range of the supply voltage and the forward voltage of your LED's. You have to make a compromise. The lower your forward voltage, the more even the output will be over a range of voltages and the lower your shut-off voltage. However, the higher the forward voltage, the more efficient your light is.

As a reference point, I have some LED truck taillights and they are 4 LED's with a combined forward voltage of 8V. The designer chose stability over efficiency.

In an efficiency-crucial application like bike lighting, it probably makes sense to use a voltage regulator. But that's another topic.

Hey, thanks about the wasted energy hint. Ill look around for red LED MR 16's, here in finland..

Have you thought of using 2 1/2" plastic drain pipe with cap fittings on the ends? Would your batteries fit?

Mounting question:

I am building up a fixie for winter commuting/training and since I have no need for the downtube cable/shifter bosses, I was thinking they may be a great attachment point for lights. It would be close to the bottle battery so wiring would be short and sweet and it would keep the bars clean. Plus, it would illuminate the front wheel and let folks know "bike!"

Has anyone done this?

Thanks for the suggestion. I'll check it out. I guess I need to spend more time at Home Depot. :o

Would you smack the lights with your knees when out of the saddle?
Depends on your bike's geometry, but when i'm on the ends of the bars, my knees are swinging through that area.

I was eyeballing it, and I think it would be okay.