Experiment with a 12v 20W bulb......

I picked up a 12 volt, 20 Watt bulb for an experiment. This is what I did.

First, I used 3 of the battery tubes from the 3C Radioshack aluminum flashlights I picked up, and stuck 8 C batteries in the extentioned tube, with extra spring to make up for the extra space. I hooked up the 12v, 20W bulb and then (when it became dark outside) I took it, along with my Brinkman LX outside for a little test. I was a little surprised by my discovery. The Brinkman LX was still a little brighter, and much whiter.

The question is, since this was just an experiment (done just because of the ability to attach battery tubes from RS flashlights), and since I assumed that the 12v, 20W bulb would have the proper amount of voltage from the 8 C size batteries, was my initial hypothesis wrong in that it would be an extremely bright flashlight? I mean, you can imagine the length of this flashlight, and since the Brinkman LX is a fraction of the size, with better light, I can only assume that I did something wrong, or hypothesized wrong.

Lemlux could tell you, but i think that the problem is that the alkalines probably couldnot keep up with the current needed to drive that bulb appropriately, hence, yellower light.

Hmmmmmm, . . . . .I think I see what you mean. That could have been the problem. I wonder if I used 2 6V lantern batteries if I'd be in the same situation? I guess this is a scenerio where lithium batteries would be best.

Also, I wonder how fast that particular bulb would deplete the C cells? I only turned it on for a few seconds.

Yup it is because you're using alkaline cells, they just drop too much voltage under load. Large D cells will do a similar thing, so will 6v lantern batteries. You would actually be better off with 10 to 12 NiMH or NiCad AA cells, they won't drop nearly as much. And yes you could also use lithiums, either AA's or 123's. If you really want to use alkaline, try 10 C cells, then 11. Just check the voltage of the whole setup with the lamp on. It might work, but it will still dim as time goes on. I made a backup battery for my cell phones and I used 10 C cells and it works fine, but the cell phone only draws about 3 watts.

You're trying to draw over 1.6 Amps from the cells, it's not going to work for very long, if at all.

Thanks for the input guys! This was definitely an experiment. I wasn't trying to make a real flashlight out of it. The bulb was only $2, so the experiment wasn't costly at all.

Your best bet would be to hook up one of those hi capacity battery packs used by many cordless drills/saws of about 14v or so, they are designed for the amperage draws. I use one for my HID mod.

I've done this, but using 7.2V nicad battery packs which are commonly used for RC cars.

I hooked 2 of these together in a serial configuration to give 14.4V (actually started at about 16v since the packs have a higher voltage when fully charged)

I was able to run a 12v 50w halogen MR16 lamp at full brightness for about 15 or so minutes with it..

Graham