Flashlights-for-dummies

I need help. I'm confused. I want a "flashlights-for-dummies" explanation of the relationships between battery voltage, lamp ratings, rechargeable vs not. Consider the following example, which focuses on my Petzl Zoom headlamp.

My Petzl Zoom takes 3 AA-cells, which means 3 * 1.5 = 4.5 volts.

However, I want to use rechargeables, so I stick in Ni-MH 3 * 1.2 volts = 3.6 volts. This results in low brightness and shortened life. My questions are these:
Is the diminished brightness a result of the lower battery voltage? What if I put in a lower rated bulb? Will it be brighter?
If so, what if I put in a bulb rated for the 2 AA-cell Petzl Micro (i.e. 2 * 1.5 = 3.0 volts)? Is 3.6 too much voltage for a 3.0 bulb?
Is the lower life a function of 1. incorrect configuration in respect of bulbs/battery voltages or 2. a fact of life with rechargeables?
Do I need to consider mAh's in any of this?

I'm going to probably get a 4 D-cell Maglite and go through the same exercises. Any help is appreciated.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Peter:
I need help. I'm confused. I want a "flashlights-for-dummies" explanation of the relationships between ..........Any help is appreciated.<HR></BLOCKQUOTE>

Peter, I would like to answer you, but ......

(Do you mind if I also read any replies to your topic ? )

lite-lover

Where to start. The biggest problem you are describing is due to voltage. So you would need a lamp rated for 3 "rechargable" cells to be bright. A 2 cell alkaline lamp would be very bright, but not for long.

It is very hard to say lamps are rated for specific voltages because lamps drop the battery voltage to a certain point and that is the voltage they make the lamp for.

So say you have a 1000 mA 4.5v lamp. Now is this lamp made to run at 4.5v or 3 cells? If you put a 1000 mA load on 3 C cells you will be at about 4v. A 4.5v 100mA lamp wouldn't drop the battery voltage much at all. It also matter what size battery you use. If a lamp is made for 2 AAA cells and you connect it to 2 D cell it will burn out rather quickly because the D cells won't drop voltage as much with a small load.

So a lot of companies are now switching to 2 cell, 3 cell, 4 cell and so on. This is because as they draw more power the voltage drops so they adjust the lamp voltage to match this.

I probably just confused you even more, hopefully not to much though.

Brock

Let's use a 3 D cell Mag Light as an example.

Your best set up is with the Carley Xenon Star lamp and alkaline batteries. This is rated at 3.8 V, 0.84 A and 4.3 spherical candlepower. Note that the lamp is NOT rated at 4.5 V (3 x 1.5 V), because alkaline cells decrease linearly with use, going from 1.5 V to 0.8 V. Thus, Carley uses about 1.2 V for an average voltage as a nominal figure. If you were to use NiCd batteries with this lamp, it would be dimmer than with alkaline cells to start with (NiCds operate at 1.2 V average), and would actually not last as long (which is to say the lamp would burn out prematurely), as the AVERAGE voltage of the NiCds is higher than the alkaline cells (the lamp voltage stays at 1.2 V for a long time, nearly the entire life of the charge).

If you insist upon using NiCd cells, use the 4500 high capacity ones, and a KSR (Krypton Star Rechargable) lamp; say a KSR 1.7 A. This lamp is rated at 3.7 V, 1.7 A and 7.5 spherical candlepower. You might (I did) think that this set up is the cat's pajamas; for a long while it was; it was the brightest thing going.

Now, however, with the XS series lamps, this set up is obsolete. Despite the higher candlepower rating of the KSR lamp, the XS lamp is brighter in actual usage. Further, the XS lamp will burn 10-12 hours on a fresh set of batteries, and the KSR set up will only last 90 min.

The only real use for KSR lamps is in cold climates; the heat produced when the lamp burns will help keep your hands warm!

Hope this helps, Walt