My first homemade (Mag) bike light

I just finished a simple conversion of a D Maglite head into a bike light. I used the head and the cap. I wedged the cap, which barely fits into the head by using a strip of rubber around the threads. It's very tight. I used a 25 watt halogen bulb (MR16 I think) and a bulb socket (which made a rather tight fit. I drilled a hole in the cap and used a DV power jack. I drilled and threaded just behind the knurling and installed a clip on light base from an older Cateye. So, it snaps on nice and tight.

NOW, my question. I'm using a 10 AA case full of rechargeables. I'm using 2700mpha batteries but am surprised to only be getting about 25 to 35 minutes run time. Does this run time sound right? I though I'd get at least an hour (my commute time).

I'd appreciate any advice. By the way, I did investigate using a bright LED replacement for the halogen, but this is all new to me and it seemed to involve some things I didn't really understand. Also, the light didn't seem as bright.

(Riding where there's) NoShoulder

This is my second post - and the second one I've not recieved one reply to. Is there something I should know? Do I offend?

NoShoulder

NoShoulder said:

This is my second post - and the second one I've not recieved one reply to. Is there something I should know? Do I offend?

NoShoulder

Click to expand...

Well I would respond if I knew what you were talking about :wave:

Just give it a little time

NoShoulder said:

This is my second post - and the second one I've not recieved one reply to. Is there something I should know? Do I offend?

NoShoulder

Click to expand...

Pictures dude...

Pictures.......





:welcome:

I have no idea about you`r question either...

I think more details would help.
I'll assume that the 10 nimh are wired up in a series to give you about 14volts fresh off the charger. However, how much current will your 25watt bulb draw on that voltage? You really need to measure that with a DMM.

How did you come up with your estimated 1hour runtime?

A lot more details needed (& of course pics :laughing

EDIT: btw - :welcome:

Yeah, I was a little impatient, sorry.

DMM? (Oh, digital multimeter, right? What setting?) I really don't know much about electronics. I thought I had gleaned that - on average - one could get somewhat less than a one to one time-per-amp/hour. That is, I assumed if I use a 25 watt buld with a 2.7 amp/hour collection of batteries I could get some known ratio of time, which I thought I noticed from other posts would be 2.7 hours - or less. I realize this is not really good math and grossly over-simplified, but I'm working at a grossly uninformed level as yet.

I know I'd get more time from a lower wattage bulb - and that's a possibility. 15 watt would be okay. But, if I just need to go to 10 C's or D's, I guess I could do that (heavier route) too.

I like the pics in this forum and I'd like to post some, but I really don't know how yet.

By the way, I discovered today that a plastic zip tie cut to length and used "on edge" makes a perfect spacer between the bulb and the lens.

Thanks for your answers so far. Oh and yes, I get about 13.6 volts off the charger. That's another thing, my charger monitors and shuts off with some batteries but not with others. Anyone know why that is?

Thanks

NoShoulder

Used it for the first time tonight. Great!

I'm so familiar with the ride, all the places that were such a pain were so much easier and safer.

I'll post some pictures in the next day or so of the light; mounted with beam shots and semi disassembled.

NoShoulder

Doh!Nut said:

When you say "shuts off with some batteries before others"

I guess you mean you charge the batteries individually and then put them in a holder which raised two points. The standard plastic battery holders are not good at high currents - they have too much resistance.
Also if some batteries are taking a different amount of charge than the others they may have gone bad. (dont know why) but the end effect would likely be that the pack would only give the capacity of the weakest cell.

The expected capacity would be
10*1.2v*2700mAh = 32400mWh = 32.4 Watt Hours. i.e give 30 watts for one hour.

A 12v 25W bulb powered with 14v will use around 30Watts so you should get around an hour. - you are correct half your run time is missing.

For a cheap incandecent bike light I have used 6v bulbs with Tamiya 7.2V R/C battery packs, these are cheap, easy to charge, slightly overvolt the bulb and designed for high current - you may even have some already.

Click to expand...

Thanks. I will use the info you provided.

NoShoulder