Mag Questions

[sandman]

1. If you put 2 3toD in a 2 D mag with a 6 cell white star bulb what would be the running time?
2. If you put 3x123 in a 2 C mag with a KPR-112 what would be the running time?
3. If you put a 6 cell bulb in a 3 D mag would it make it brighter and would you lose running time?

 

[shankus]

First, Welcome to CPF, sandman!

The first two, I don't know enough about, but the third, I can answer.
The 6 cell bulb is designed for 1.5V X 6 = 9V.
If you drive it with 3 cells it will be driven by 1.5V X 3 = 4.5V. Considerably underdriven. Definitely dimmer. I'm not sure about the details of efficiency of a bulb driven at spec vs. underdriven, but I know the light will be very yellow, if not downright brown (Yuk!).

I don't know what runtime you're looking for, but I bet we can help you find a light to match both your needs, and that "Bright! Runtime be damned!" streak that all of us have a bit of.

Why not try a two cell Mag bulb in it for start. A bit of overdriving. You'll notice that the light will be a bit whiter and brighter.

You're in the right place for runtime considerations, as well as brightness. You may find out that LEDs provide equal brightness (and better color), and longer runtimes than the incandescents of yesterday.

Again, welcome to the forum...

 

[sandman]

First, thank you for welcoming me to your wonderful forum.
I have read a lot in the last two days and I still don’t know what underdriven and overdriving mean.

 

[MR Bulk]

Welcome aboard! You'll have to wait for the incand. modding gurus to respond to your questions, but believe me when we say, "Bright is right"!

 

[Pellidon]

Guru? no. But here is what I have gleaned here.

Best way to determine run time is to measure the current draw and divide that by the capacity of the batteries in question. Energizer has a chart here Energizer capacity charts That will give a rough estimate.

Using a 2 cell lamp in a 3 cell will result in a brighter, whiter light. For a few seconds as 2 cell lamps don't seem to like being overdriven by 50% (cell count). A better fit is to run a 4 cell light with a 3 cell lamp. I have had several blow on the second or third turn on.

Overdriving refers to the running of a lamp at a higher voltage than it is intended. A 2 cell lamp is rated at something like 2.4 volts or so. This means that they are slightly overdriven at the 3 volts of a fresh pair of batteries. Jacking up the voltage to 4.5 (3 cell) would double the rated voltage almost for the 2 cell lamp. This increases brightness and improves the color of the light some. It also increases the current draw and reduces the run time and the life of the lamps.

I have a 2C mag converted to 3 x 123's using a peice of PVC pipe for a sleeve and a 6 volt lamp. very bright and white while batteries are fresh. Nice handy form factor and packs a wallop. Much better than a 6D mag size wise /ubbthreads/images/graemlins/smile.gif

 

[sandman]

When you have 3x123's it equals 9 volts. When you have 2 3toD's it equals 9 volts.

What makes one brighter then the other? Let’s say you are using the same bulb in both and they are supplied with 9 volt each. Wouldn't that mean the same brightness?

 

[Ginseng]

Hi Sandman,

No gurus here, just a bunch of guys who have blown many a bulb in the elusive search for bright/cheap/small.

I think Pellidon has given you good leads on the runtime questions and shankus has addressed the 6-cell in 3D question. As to 3x123 vs 6xAAs, they are three quite different circumstances. First of all, you have three battery chemistries at play. Lithium in the 123s, alkaline and either nicad or nimh for rechargeable AAs. The 123s may deliver slightly more than the 3V nominal and will service up to 2.25A without much problem. The alkies have the highest internal resistance and though rated at 1.5V, may deliver less power than nimhs which have lower IR and are rated at 1.2V nominal. In practice, I've found that the more demanding the load, the better nimhs will perform relative to the alkies. I don't have enough experience with nicads to comment intelligently.

For example, I have a WA01318 bulb. Rated at 9.6V and 1.93A, it is an 18.5W bulb and reasonably demanding of the power supply. It is very, very bright on 5x123. Very bright on 4.5x123 and about the same on 10xAA. So in this case, 10 cells = 4.5 cells. Another bulb, the WA01185 is very bright on 9xAA, very bright on 9xAA and less bright on 4.5x123. so in this case, 10 cells = more than 4.5 cells. Why? Because the WA01185 is a 9.6V, 3.15A, 30W bulb. The lithiums cannot adequately supply the needed current so it's dimmer than on an equivalent number of nimhs.

I hope that helps.

Wilkey