trekker pete

Has anyone ever tried using one of these to power a bike lighting system?

I plan on commuting through most of the year and a fair portion of my 12 mile ride is on poorly/non lit roads, so I will need a bit more than a flashing 'see me' type LED light. I would also have see me type lights mounted so I wouldn't need the big light for more than about 20-30 minutes each way. I would be able to recharge at work if neccessary.

It just so happens that a craftsman 18V powertool battery fits perfectly in a water bottle cage.

Any suggestions on what light would be compatible to this power source would be appreciated.

thanks,

Pete

cyccommute 

18V is probably too far over the nominal voltage of a 12V halogen to be useful. While you can use 14.4V on a 12V halogen and get away with about 10% of the life, jumping to 18V will likely pop the bulb the first time you turn it on. Better to use a 14.4V system and not risk too premature blowout. A 20W 12V bulb overvolted to 14.4V will burn for around 2 h on a 3.3 Ahr battery. RC car batteries in that capacity are readily available and dirt cheap.

n4zou

+1

https://www.dealextreme.com/details.dx/sku.7621

trekker pete

Wow, those things are cheap. I thought Lithium batteries were big $$$$$. Looks like it is the way to go.

I guess halogen is the way to go for the lamp or can I get enough light out of LEDs? I would like to go with the LEDs if possible for their ruggedness and efficiency.

cyccommute 

That battery is too low a capacity for a decent halogen system. You'd get 1500+ lumens out of a 20W 12V halogen but only for about 40 minutes. N4zou has plans around here for LED systems that would run for a long time at a lower light output on that battery.

trekker pete

I could go with 2 or more batteries in parrallel. Or are there issues with doing so?

I think I will look into the led systems.

thanks.

n4zou

Everything you need to know and build a very bright LED headlight is here.
https://pilom.com/BicycleElectronics/...lectronics.htm
P7 extremely bright battery power only power LED.
https://www.dealextreme.com/details.dx/sku.12721

Power LED suitable for dynamo or battery
https://www.dealextreme.com/details.dx/sku.2394

Triple LED dynamo or battery powered DIY bicycle light.
https://www.candlepowerforums.com/vb/...d.php?t=186066

cyccommute 

No issues but 1.8 Ah is still low for a halogen. Halogen will throw a ton of light and the efficiency of an overvolted halogen is quite high (62 lumen/watt for a 20W MR16) but finding low wattage halogens for longer run times, like 10W, in MR16 is difficult. To get an idea of run time, multiply the ahr rating of the battery by 0.72 which for a 900 mah battery (0.9 Ah) is .6 of an hour. 1.8 Ah would give you 1.2 hours. (Those are estimates. YMMV)

The battery capacity is additive up to a point. Each pack has it's own internal resistance that will reduce it's run time and that can vary from pack to pack. That probably wouldn't be a problem for any group of packs below 3 or 4. More than that and you might see an effect.

Honkey Kong

I have used a Auto Driving light, replaced with a 15W bulb (hard to find) and have been running it off an 18 Volt Ryobi battery for a while (light use). I can get 1 hour+ run times. Overvoltaging the bulb will decrease its life but dang its bright. I've used it maybe 10 hours total. Went for a ride with the girlfriend the other night. I gave her the bike with the big light on it and I could not ride in front of her because of the shadow it created right in front of me. It also drove me nuts because I could not tell if a car or her behind me.