Novakane 

First some brief background info:

Previously I had purchased an MR16 halogen lamp and some PVC pipe adapter pieces.
I modified the tubing to have a beveled surface and silicon sealed an MR16 into it (replacing a bulb involves removing sealant and gluing in another. Not too big of a deal).
The bulb part friction fits to a threaded piece that screws onto the mount already attached to the front of the bicycle - so the main light portion screws off for maintainability but seals on otherwise.

So, I've got a slick light. No power.
I came across an awesome deal where I got 2 batteries and 2 chargers - 6.0v 1000mAh NiCd cartridge batteries for R/C toys. By wiring them in series I can drive the halogen very brightly - I've not made a holster for it yet so testing involved pressing wires by hand - hard to hold for a long period of time.

Here's my questions:

Has anyone tried this?
Would I get a longer run time if I used two sets of batteries, running them like packs of 12v in parallel?
(ie. 2x6.0v in series, treated like a single battery)

I don't know my run time yet for the reasons mentioned above, but was wondering if anyone else has tried this.

DaveSANYYZ

I haven't tried it. If you run the two x2 packs in parallel though, you will double your run time.

6V @1000mAh... wouldn't the "normal" 2Ah rechargeable AA's give you better capacity? Not sure of the difference in sizing and price though. Perhaps with the R/C battery pack, it's more convenient than handling individual AA's.

cyccommute 

You can run them in parallel but don't expect much run time out of them. 1000 mAh is pretty low for capacity. To figure the run time


Your maximum possible run time would be 36 minutes. And you'd probably not reach that. You could band together 4 packs (2 ea in parallel and then 2 of those in series) to get to 2 Ahr but that will only give you about an hour. There are better, higher capacity packs out there. Look at Battery Space. You could even boost the power to 14.4 V and get a high light output.

n4zou

Instead of using that power hog MR-16 halogen you should build an LED light. DX just listed a triple aluminum LED reflector for Cree and SCC high power LEDs. Here is the link.
https://www.dealextreme.com/details.dx/sku.11922




Load it up with three Cree XR-E Q5 Emitters driving them at 1 amp and you get 675 LM.
A 20 watt halogen MR-16 is about 500 LM. You can also use a driver that allows dimming to save power and being nice to oncoming traffic. Most also have a SOS blink mode, three long flashes followed by three short flashes and continues until you switch modes.

cyccommute 

A 20W MR-16 puts out 850 lm at 12V. A 20W MR-11 puts out 400 lm at 12V. Boost the power to 14.4V and the output nearly doubles.

One of the allures of a DIY halogen system is the simplicity. A battery, switch and a bulb give out an incredible amount of light. Adding electronics just complicates stuff.

As for dimming lights for oncoming traffic...kinda defeats the purpose of throwing out a bunch of light, doesn't*



*Please note that I do aim my lamps down so as not to be blinding oncoming traffic but they can't ignore me

Novakane 

Indeed, my plan had originally called for 2500mAh rechargeable AA batteries - connected in series to make 12v - and it may still end up being that way. These R/C batteries with their chargers where a super deal that I couldn't pass on the opportunity to at least give it a try.
I was wary of the 1000mAh and other responses here have confirmed my theories (and fears) about these batteries for this purpose.

Now that the theoretical aspect is handled - I'm going to try to wire something up and see just how long they last in practice. If I can pull half an hour out of them I'll be satisfied enough to purchase two more and increase the mAh's.
What particularly attracted me to these was:

a) the price
b) 3 hour charge time - if I kill the batteries, I have two chargers and can get both back to full capacity in 3 hours - 6 hours if I use 4 batteries. This is shorter than a work day, so I can refresh the whole system for the evening if I end up killing it in the morning.
c) I don't usually ride for more than a half hour in the dark, so at least that (preferably an hour capacity) is all I'll really need.

The biggest downside is a lack of easy to find receptacles. (I can get AA holders cheaply, anywhere...)

Novakane 

Ok. I spent the last half hour rigging up a battery holder / connector / switch combo. For now I just hard wired the halogen into the battery pack since I didn't have the male connector for the system available and had limited patience for how much fussing around I was willing to do for a proof-of-concept test.

I've just plugged it in, and on fully charged batteries this thing is very bright. Now to sit and wait to see how long it will stay that way.

Novakane 

That worked out quite predictably. The light put out a consistent (as far as I could tell) bright light for a little over a half hour. After 30 minutes it began to dim noticeably, becoming impractical for use at about the 40 minute mark and totally dead around 50.

This leads me to be fairly confident that adding two more batteries would likely provide an adequate run time for my needs, however I'm going to complete it for now with just the two - most of my evening riding is fairly utilitarian and accomplished within a half hour at the most.

I did notice that the PVC housing got quite hot during this test, but did not melt. I think that it will be just fine with the breeze of cycling running along it.

When I have access to a digital camera I'll post some pictures of the project.

66aldo

Parddon the noobness of my question, but I was looking at Walmart for 20w MR16 bulbs and they didn't have any. They only had 50W ones.
How would this affect the light output and/or run-time, given the same 14.4v battery/power source?

DaveSANYYZ

Assuming the batteries can keep up with the demand for the current draw, it will have a 2.5x shorter duration. 3.47 A... I wouldn't try it.

cyccommute 

Look at the formula I gave above. It's pretty simple math. Assuming a 3.3 Ah battery at 14.4 V, a 20W bulb will give you 2.3 h (best case). A 50 will give you 0.9 h (best case). The light output of the 20W will be around 1600 lm...which is incredibly bright. The light output of the 50 will be around 2000 lm...which is stupidly bright...even for me

Look at Battery Space for 20W bulbs. I prefer the 12 degree spot to a flood.

Novakane 

I bought my bulb, all the PVC fittings as well as the silicon seal at Home Depot. They're pretty tolerant of me walking around the isles picking up random things and staring at them for moments on end while I imagine something they where never intended for...

The 20w light appeared to be pretty bright running from 12v. I'm sure that if it was done properly with 14.4v it would be perfect. 50w would be overkill, unless you plan to back it up with some serious power.

Hindsight being 20/20 I would have bought 7.2v power packs and chargers, but for some reason 12v was in my mind since I started this project a year ago, the details where hazy when the opportunity rose. Ah well, for $20 I won't complain for an education.