Maybe I should try a seperate thread (or the battery forums), but I've got a question you might be able to answer:

I just ordered the 3500mAh, 12V NiMH battery from batteryspace with what I *thought* was a smart charger, but it turns out it wasn't. It's just a 400ma wall-wart.

I do, however, have a DeWalt drill charger suitable for modding. I know it'll handle that voltage/capacity, but it's designed for NiCad. Is it safer to use the dumb charger, or a charger designed for NiCad (that's using delta-V, I suppose)?

It's definitely safer to use the NiCad charger rather than the dumb charger, NiCad and NiMH have similar charging characteristics. The question is really how smart the NiCad charger is. I would recommend getting a smart charger; you can get one for around $20-30.

Ok, here are some pics of my set up. This is far from original as everything is pretty much already posted here but it may be useful for others to get an idea of how all looks together. First pic shows the whole thing. Second pic shows a close up of the Minoura clamps in action. Third pic shows the bag that contains the battery, fuse, and switch. Fourth pic shows a close up of the switch and fuse and the soldered connections covered by heat shrink tubing.

Nice job, JZ. Neat and professional-looking. Have you tried mounting the lights under the bars to perhaps give more contrast for seeing potholes and other road hazards?

Thanks. I am pleased with the results and have used one of those black cable spirals ties to wrap the two cables together and it look even neater now. I tried putting the light under the bar but that spot seemed too crowded with brake and gear cables + battery + lights so decided to put the lights on top. I am still exploring different bulb combinations. I am now running 35W + 20W and have tried 20W+10W but will be trying 20W + 20W and 35W + 10W and see which combination I like the most. I can also put a third light on a helmet mount because I have switches for three lights and am currently only using two, or place one of these two on the helmet. There are many options. Actually, I think that is the main advantage of building your own lights. It allows you can try different setups until you find the one that best suits your needs or preferences.

Two quick questions for you:

1) Do you think I should tape the vents on the rear of lamps to prevent water from going in? Should I try riding under the rain and see what happens or what? These light were designed to go on the outside of a car so they are probably fine as they are but those open vents make me slightly nervous.

2) Do you have any suggestion for a helmet mount? I am thinking on attaching the spare Minoura clamp that I bought to a piece of plastic and then Velcro that to the helmet.

Awesome setup...Seen any differance in how the drivers treat you?

jz19,
Are you planning on adding a strobe or taillight? I'm still debating where to put the switch and battery. I'm a bit partial to a handlebar bag since my trunk bag already carries lunch and clothes. Your setup looks pretty good. Love the inline fuse between the battery and switches. I'm getting one that looks like it from radio shack today.

I'm using the same optronics bulb case (only one) with a 20w bulb. it bolted right on to the fork bridge on this Downtube folding bike I recently bought as my full time commuter. Velleman xenon strobe on the rear and I am using a 6Ah SLA battery that comes pre-packed as the "Vector portable Power" unit discussed very early in this thread - which includes an in-line fuse, 12v accessory outlet and water resistant case. with the 20" wheels, the battery pack fits neatly under the rack so I can still have the child seat for taking my daughter to day-care. I am very happy with the setup and all the advice Ive received here. Just bought my switch and some more wire to get things routed more neatly, but it's pretty much done!

Well, my commute is mainly bike trail so interaction with cars is limited but the lights are very visible even with surrounding light. While I have turned on both at the same time the combined 55W would be too much for the battery and sort of a waste of energy with two spots as I am currently running.

I bought an amber strobe as recommended in this thread but will not be installing it unless I start riding on the streets more. If you look at my switch box you will see that I have three switches which would allow me to install the strobe or a third light with a helmet mount without much hassle. About the strobe, I have tested it and can tell you that there is no way for a normal blinkie to be that bright and annoying so go for it if you need a taillight. Before deciding on that handlebar bag from Walmart I tried a frame bag and a trunk bag but this one was the clear winner as it has the perfect size for my battery and has an external compartment for the switch and fuse. Btw, I got the fuse and switch box from Radio Shack.

Very nice setup. The Vector battery pack looks great and would have cost less that what I spent in a battery, case, fuse, and two chargers but I somehow managed to miss that one. It is easy to miss good information in this thread because of its size. Anyway, I already have all this soldered together so I am past the point of no return.

I'm not familiar with the light units you used but if they are designed to be mounted on the outside of a car I wouldn't cover the vents. A 35 Watt bulb puts out a lot of heat.

If you can, cut slots in the plastic and use velcro straps to fasten it through the vents in the helmet. Just gluing velcro to the plastic and to the helmet may not be secure enough.

Ye gods, what have I done?!?! After a year, I've finally finished my homebrew Luxeon I tail light! It is a Lux-I, MicroPuck regulator, two AA batteries and a 5x20 degree oval-beam lens. The housing is just a clunky plastic shell with RTV to seal the window, so don't ask for pix, I just wanted to finally get it done with parts-on-hand. Anyhow, I noticed that cars are not passing me despite plenty of lane width, which is annoying because they're on my tail slowing traffic to the 7-10MPH crawl I do up this hill. When I got home tonight I decided to take a look before turning on the garage light. I was blinded at 25 feet, and could barely see the bike beyond the light! Ouch! I even had to look away from the light after turning the garage light on. I may have become one of those annoying jerks blinding other traffic with too-bright lights. I'm considering cutting the power to a single AA battery to tone it down. Are there laws about too-bright vehicle lights?

Finally making progress on my quad Lux-I headlight, too. It sucks that I don't have (legal) access to a shop milling machines or lathes anymore.

Nicely engineered, and it seems like drivers see you, and that's what most of us here are trying to accomplish. Do you really think it's too bright? How does it compare to a car brake light? The reason I ask is I'm building a tail light/stop light that uses four red 1 Watt Luxeon Stars. They will be running at 10%, or about 35 ma. for tail light duty, and the full 350 ma. when I hit the brakes. Two will have the 5 x 20° oval optics and the other two will have 25° wide angle optics. If I find that they are way too bright, instead of reducing the drive current I will experiment with the optics to get wider visibility. You might want to pop in a 25° optic if you have one to see how it compares to the oval for brightness.

If the light is intense enough that drivers tend to looking away, then they aren't seeing ME in a useful way. (The same thing that happens when an oncoming car's headlights are too intense - other drivers become unable to see a large part of the whole road ahead of them.) My beam is much more concentrated than a car's tail-light, I think. The fact that people are hanging on my tail at 10MPH when they could easily pass seems to indicate a possible problem, besides being a bit nerve-wracking. I really worry about the guys behind the first one who've been shielded from seeing me until the last moment when they finally pass. My night route is up rolling hills, so the up-down angle of the light to the observer varies a bit with their distance, which makes it hard to optimize. I might try changing the direction of the beam side-to-side a bit, though. The problem is monster trucks with over-wide tires are all the rage here, and these kids can hardly keep their big rigs on the road sometimes. Those are the guys I don't want zooming by, and I have to tip the light up farther for them than for a car, so the poor people in sensible cars are getting screwed yet again. I was surprised by the intensity of the beam in the dark, though. That oval beam lens works really well for a tail-light.

I thought some of you might want to see some more light solutions so here is mine that I built over the weekend. The two up top are just led lights that was previously using and I leave each on blinking so that I get noticed. The other light is the typical 20 watt MR16 that is run off of a 12volt 3.4 ah SLA battery that fits nicely in the seat pack.

WARNING regarding TrailTech HID.

FIRST: The TrailTech HID is a GREAT light. I have no problem with the light itself. Just to make that clear up front. It's a sweet lamp and the company is outstanding.

HOWEVER, I bought mine from BatterySpace.com, and they recommended the 14.4v NiMH battery as being "perfect" for the DIY HID lamp. So that's what I went with.

My HID lasted 3 hours before dying. Since I hadn't installed it for 6 weeks after buying it, BatterySpace wouldn't fix it (30 day warranty). TrailTech stepped up though and fixed it for free. Yay!

Turns out the problem is that the light (ballast) was fried due to overvoltage. The 14.4v battery that BatterySpace recommends delivers in excess of 14.8v for over an hour on a full charge at the load of the HID lamp. 14.8v is the maximum voltage that TrailTech says the HID will take without damage.

Normally their On/Off switch has a regulator in it that keeps the lamp from getting too much voltage. But if you buy just the raw lamp and hook it directly to power, there's no protection.

So, a warning; if you buy the raw lamp, buy a 12v or 13.2v pack, NOT the 14.4v. Either that or use a voltage regulator.

I am going to use a voltage regulator, but you probably don't want to use a conventional (linear) one; they have a lot of inherent loss. I'll be using a zero-overhead switching regulator, so the loss will be just one or two milliamps.

I hope this helps someone keep from frying their light.

Thanks for the heads up. I was considering buying one of these from Batteryspace because of the price. They also sell the TrailTech light with their "14.8V" Li Ion battery pack which puts out 16.8V fully charged.

Can you give us some details on the switching regulator you are going to use?

I will try to find the schematic for it. It's very simple, all it has is one MOSFET, an op-amp, a capacitor and an inductor, and a few stray components. I think it costs about $10 in parts and builds in an hour or so. The great thing about it is that it will put out 12V on a 12V input (most regulators drop at least some voltage) and it has very high efficiency. Normally regulators waste the volts that they drop as heat; this one doesn't.

Ok...I want/need in on this whole DIY lighting. So...I've read/skimmed about 80% of this loooooooooooooong thread; and seen some good pics. I'm really excited to try. So let it begin! Ebay....here I come!

Ok, I'm starting to put some ideas together and I need some advice from all you battery and electrical geniuses.

Ok, so I won me some Hella Marine lights that use 12v 37.5 watt bulbs. I'll only be running one of them. My commute is about 2.5~3.0 hours round trip. According to the math I'd need a battery with 7+Ah to make the trip w/o having to charge at the office. I was looking at the option of ten 1.2 volt D-Cell 9500mAh NiMh batteries (like these) in series. That'd meet my power and run time requirements perfectly. My questions are....how do you charge such a beast? And how long would it take?

edit: Or I guess I could also use ten 1.2v 4500mAh NiMh C-Cells in series+parallel to get 12v w/ 9000mAh; but the questions are still the same.

Here's a 10 AH pack that comes with a smart charger http://tinyurl.com/ab5tz, but I think a 37.5 Watt bulb is a bit of a power hog. That battery pack weighs almost 4 lb. and in cold weather you will be lucky to get 3 hours out of it. You might want to consider a 15 or 20 Watt bulb, if it will fit your Hella, and if your riding conditions permit.

Thanks for finding that battery pack for me! The bulb is automotive type and I think it only comes in one wattage unfortunately...but I'll double-triple check. I need a light that will not be washed out by car lights on wet pavement w/o street lighting.

Is anyone else on the thread still runnning an automotive bulb solution? What sort of battery tips do you have?

The rule of thumb is that you need to derate battery amp-hours by 50% for real-world applications. There are two reason for this -- first, most batteries don't last too long if they are completely discharged, and second, the ratings are usually for a 20-hour discharge; faster discharge usually delivers less power. So with a 37 watt bulb and a 3-hour commute you need more like 18 Ah of capacity. That is beyond commonly available NiMH battery types; I'm not sure where you'd get that capacity. I would not recommend running rechargeable batteries in parallel. Basically, there are two things that destroy batteries -- overcharging, and complete discharge. The more individual cells you have in your pack, the more likely that one cell will be overcharged or completely discharged without you noticing. Once that happens, the pack is toast.

The pack that multibiker linked to looks like a good starting point. Batteryspace is the only place I know of that sells smart chargers for NiMH packs of more than 8 cells. As the number of cells increases, the smartness of the smart charger has to increase as well, for the reasons noted above. Note that this pack is 12 cells. One problem with NiMH is that the voltage declines pretty sharply as the cells discharge. While NiMH has a nominal voltage of 1.2 volts, a fully charged cell will be about 1.4 volts and a cell at the limits of usability will be about 1.0 volts. So this pack delivers a minimum of 12 volts, an average of 14.4 and as much as 16.8. For a halogen bulb rated at 12v this is actually a pretty good fit, as halogen bulbs are dramatically more efficient when over-volted. Over-volting reduces bulb life, but typical life ratings are in the thousands of hours and I always break them by crashing or dropping them before they burn out. FWIW I have a 12-cell NiMH on my bike with 12V halogens, and I use the BatterySpace charger.

So this pack gives you a "budget" of 9.5Ah. I would work backwards from there. Derating by 50%, a three-hour run time puts you at about 20 watts. For my money, there are only two bulb types worth using on bikes, the MR16 which is 2" in diameter and comes in a variety of wattages and beams, and the PAR36, which is 4" in diameter and comes in 14 or 25 watts, flood beam. For the MR16 the consensus is the Optronics housing is the way to go; I use this housing: http://www.northerntool.com/webapp/w...4&storeId=6970 for my bike with the PAR36. Both of these housings are automotive, in answer to your question "Is anyone else on the thread still runnning an automotive bulb solution?" although probably not the answer you were looking for.

You'll have to figure out what combination of bulbs to spend your 20 watts on. What a lot of people do is have one flood light and one spot light. There is not a whole lot of choice available in 10w bulbs, so your best bet may be to use 2 20w bulbs and wire up a switch so you can switch between them. Depending on your commute, it also may make sense to use a 10w or 14w for normal conditions and the 37w you have for high visibility times.

Thanks DCCommuter; that was just what I was looking for!

Good news! I think found that my Hella housings will also accept a bulb that's only 27 watts! That should give me some more breathing room when it comes to battery options.

Thanks to all that have jumped in with some helpful tips. I'm sure I'll be asking for more in the weeks to come.