Easiest way is to use a battery holder. Something like this:
http://www2.towerhobbies.com/cgi-bin...?&I=LXLX82&P=7

I just had to add this (it's about high-capacity batteries, so very relevant to this thread):

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When you are on business or having a trip with a splendid mood, your portable computer is absolute a indispensable assistant for you. However, because of the limited using time and high price of the built-in battery, you may be done harm to by that, of course , you are very boring.

Can the problem be solve? The answer is definite YES. Our shop focus on all kinds of tailor made notebook computer piles such as 7.2V, 10.3V, 12V, 15V, 16V, 17.5V, 18V, 18.5V, 19V, 19.5V, 20V,21V, 22V, 24V, etc. which the current capacity from 1800mAh---to 9000mAh even more, and output current high to 6A. each pile built-in charge/discharge protective circuit and shortcircuit protective circuit, that ehances the battery’s working period.

The new development lithium pile built-in high-efficient low temperature high power voltage transformer similar table computer’s main board’s, the offset of output voltage is below 0.5V during long time working with no any extra comsumer. The redundancy protective circuit design enable output more stable. Built-in SONY, PANASONIC or SANYO spare enable stable and long-time voltage output. This is our ensure to the consumer with high satification. And we offer charger and saving energy software and power supply interface.

On the other hand, lithium battery is much safety than AC/DC switch and light 35% than nickel-hydrogen battery.

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A 'memento mori' for any of us who pride ourselves on speaking 2 or more human languages.

Apropos battery cases...

Rather than go with a lead-acid battery (groan! they weigh a ton) I was thinking that, say, 4 or 5 12v 1800mAh camcorder (or similar) batteries in parallel should work fine. Making a case wouldn't be a complete problem, since acrylic sheets and cement are readily available. But then I start wondering about whether, clamped together, they might overheat and possibly even catch fire. Are there any double-Es posting here who can speak to the subject of overheating and also the subject of ganging them in parallel? (I jumped from p4 to here, so I don't know whether we have EEs posting in this thread)

using CFL light for a bicycle headlight?
 

Yes, using a CFL light for a bicycle headlight could work but in order to give it the best chance of working properly one would have to use a fluorescent floodlight reflector based CFL so that most of the generated light is reflected and redirected out frontwards onto the roadway surface. The main advantage is that with a 25W CFL floodlight reflector one gets about 700 lumens of light generated which is approximately in the neighborhood of 50lumens per watt as compared to 15lumens per watt via incandescent means of light generation

Just added a Light Brain Twin to my dual 20 Watt system. http://www.trailheadlights.com/

Neat little circuit, now I won't have to run 20 watts on the bike path.

Installation was easy, and it worked on power up. First commute with it is tonight.

If you use the radio shack battery cases, particularly the multi cell ones, the batteries will pop out at inconveniant times. I finally used some sheet styrene on each side of the case, held in place with a pair of zip ties to keep the batteries in. Also, if you use the nine volt battery style connectors, get the heavier duty ones. The cheap ones just can't handle much handling.

In general you must be very careful when connecting packs in parallel. A failed cell can easily overheat as the good cells will discharge through the failed one. Only connect matched cells, or cells designed to be connected in parallel, and only connect cells with a similar state of charge.

Sealed lead acid water bottle battery (sort of)
 

Interstate Batteries sells a 12v, 5.5ah battery (part # SLA0093) that fits nicely in an old-style aluminum waterbottle cage. I wrapped the battery with an old inner tube to give it some padding and make it a tighter fit, and ran a velcro cinch strap to make sure it stays put. The setup's not waterproof, but I'm not using it for commuting, so getting caught in the rain after dark shouldn't be a problem.

Wired it up to a Malibu model CL507L housing with an MR16 20 watt 12 deg spot bulb (Litetronics L-3817) and took it out to the local MUP for a test ride. Shadowed sections that I'd had to tiptoe through before were no problem. The 12 deg spot bulb still threw enough light to the sides to see a skunk running along about 15-20 feet off of the path (sprint time :D). Had to jump on the brakes to avoid a 'possum which ran out in front of me. I probably wouldn't have seen the dumb s.o.b. with my old light. I certainly wouldn't have seen the skunk.

The Malibu housing didn't have adequate support for the bulb, but some Reynolds Wrap folded up to make a shim under the front edge of the bulb's reflector fixed that problem. The housing didn't even get warm on the 20-odd minute ride.

Haven't tested the run time, but it ought to be good for at least a couple of hours. That's plenty for my purposes.

Parts used:
Battery - $26.99
Charger - 12.99
Housing - 12.96 @ Lowes
Bulb - 4.62
Hanger - .69
Strap - 1.50
Wire & connectors - 6.00
Total - $64.75 + tax

Being able to see at night - PRICELESS!!!! :D

I finally got around to taking a few pics of my new battery holder. Yea, the tennis ball can is gone.
It's a Jandd Tire Bag II. Just the right size for my two batteries.

http://home.mindspring.com/~rhorne/B...d%20lights.jpg

Here are the connectors. Just unzip the bag slightly and pull them out to recharge the batteries.
http://home.mindspring.com/~rhorne/connectors.jpg

Here's the whole bike. I had to move the frame pump from under the top tube to along the seat tube. Much neater looking than with the tennis ball can.
http://home.mindspring.com/~rhorne/Winter_bike001.jpg

I use the same housing. I folded up some Reynolds Wrap and made a shim which I slipped under the front edge of the reflector. No glue was needed to hold the shim in place.

Aargh! I have an amber xenon flasher from All Electronics as a tail light. I use a 12v 8amh (Iknow, that's a lot) SLA battery, 20w halogen headlight, and have each light wired to seperate switches. Yesterday afternoon I went out to ride and my tail light wont come on. Has anyone had durability problems with this item? Is there a way to check it without disassembling the whole setup? I've considered going to a truck/trailer multi-LED tail light from the auto parts store.
Help please.

Although I have not tried the All Electronics strobe myself, I've seen several posts about it failing. :o

I went through a couple of similar amber Xenon strobes from Radio Shack. I took them apart and found one of the two terminal wires on a big finger joint sized capacitor had failed in both of them. They were burglar alarm strobes and had not been designed for vibration. I brought one more, opened it, and half covered the big capacitor with clear silicone caulk which set quickly. That strobe has lasted for more than 10 years now. I'll bet something like that has happened to the AllElectronic strobes.

HEAT SHRINK: I'm looking to get a heat gun and wonder if the cheaper high temp (600F+) models are too hot for use around bike lighting. Those with variable temps down to about 200F tend to run over $100. Worth it?

If you mean a true "heat gun", those are designed for stripping paint. Heat-shrink tubing doesn't require extreme heat. I use dual setting hair dryer set on "hot" and it does fine. I certainly wouldn't drop a bunch of cash on a special heat gun just for heat-shrink.

If I remeber right some of the heat shrink I've seen reacts at about 240F. If a hair drier is enough to do the job well then I'll hold off on a heat gun and give my wife's Conair a try. :) Heat shrink isn't the only thing I'd use it for though. I take decals off of parts sometimes and I'd rather stop using solvent.

Still curious though: What the approx. max temp safe for activating heat shrink around bike parts? I'd rather not find out the hard way. :D

Thanks,

I have always use a butane lighter to shrink heat-shrink tube onto wire. I use a medium flame and sort of gently wave/brush the flame along the tube to gradually heat it, not leaving the flame in one place for more than it takes to shrink it, rotating the wire and warming opposite sides as I go. It takes a little practice, but I have always found it to be cheap and effective. I keep a butane lighter in my tool box for just this reason. I find that a heat gun will heat it too fast. I just wave the heat-shrink tube through the heat gun blast to slowly and gently heat it if I need to use a gun. A butane lighter gives more control for small sections of heat-shrink, especially if you have temperature sensitive components or housing close to where you are shrinking. If I am doing a really long run of heat-shrink, I pass the wire quickly through the heat-gun blast or wave the heat-gun at it (like drying hair). You definitely don't need a heat-gun (the type used to strip paint) unless you are doing a LOT of heat shrinking and can place the gun on a stand to pass the shrink through the blast.

Can anyone that made a low battery indicator share their experience

I have some schematics and names of some ICs that are built for the purpose (nanovoltage comparators) but feel like I still need a bit more info

I have read this entire thread - once - but it took so long that my memory has now failed. Exactly what does this little circuit do?

This circuit allows you to vary the light output of your single or dual 20 Watt headlamps. It will allow you to use less power if you only need a headlight "to be seen" by and then ramp up the light output to various levels (e.g., 7, 10, 20, 30, 40 Watts) depending on how much light you want or need by pressing a momentary switch that will cycle you through the settings. This saves battery power, to a degree, so you're not blasting away with 40Watts when you only need 7 Watts.

I don't know if the twin has all the features of the twin plus but other features are:

• fails over to second light if primary light fails (and you're not using both anyway)
• runs over volted at 13.2v (unless you change the default) until the battery voltage drops lower
• has warning flashes when battery gets low
• goes into emergency low power settings when battery is too low
• has SOS flashing mode
• slow starts bulbs to maximize bulb life - also helps Li-ion batteries because their cut-off circuit could trigger if connected directly to high wattage bulb(s)
• allows you to use higher voltage battery setups without damage to bulbs - e.g. I have a dual 7.2v RC NiMh setup that puts out close to 16v when charged

I have finally become fed up with the battery I'm using on my bike lights. For two seasons I've been using a portable DVD player battery, rated for 9V @ 5400mAh. It's pretty small and lightweight, because it is a Li-Ion battery. It worked great... until a few weeks ago.

This battery exhibits a strange behaviour, it automatically shuts off the juice if it detects a short/over-current. That's fine with me, because it saves the battery. However, the only way to reset it is to plug in the charger. How many people carry the charger with them, or for that matter, have a wall outlet handy? Exactly.

The other problem I've been having is the connector. The tiny 2.5mm jack just can't handle the constant strain and bumps of my daily commute, and it has become highly unreliable. For the past few days I've had to ride with one hand behind my back (literally), keeping constant pressure on the cable so my lights stay on!

So tonight, I ordered an 11.1V, 7200mAh Li-Ion battery kit from batteryspace.com. With more voltage, more capacity and *waterproof connectors*, I should be all set for the winter riding season. Now I just need to find a clever place to mount the battery on my trike...

Newbies questions regarding the MR16 (picked up from Home Depot)

does the light bulb has 12 VAC (alternating current) or 12V DC (direct current) ?

I'm planning to run this bulb thru either the Dewalt 12V battery or a 12V battery bottle. I'm assuming those battery is DC type.

Would there be a problem ?

Thanks in advance

MR 16/12 volt at Home Depot should be DC.

My All Electronics zenon strobe light arrived tonight. Looks like you would not be able to take the light apart w/o some serious damage. You might have to crazy glue the case back together.

I shook the light several times. Didn't hear anything moving around.