Minimal 20W halogen light

What do you REALLY need to make a basic high-power incandescent? Working with machinery made me confront the need for really floody, high-output light with great color rendition. Lacking funds for a top-notch high-CRI LED, I got creative.

The local Wal-Mart had LifePO4 cells at a nice price, so with those, a cheap solar light (for the T3 socket) and 20W MR11 flood bulb (with front glass), I was on my way.

The batteries did indeed light up the bulb nicely, but I was stuck - what should I put them in? I looked around. Printer, duct tape, but no pipes.

...paper. I set out to use duct tape and 8.5x11 sheets of paper to make a flashlight. One that might set fire in my hands, but that would also loosen the duct tape and shut off the light.



Momentary-on, thumb-switch 20W halogen with about 20 minute runtime. Except for durability, ease of replacing batteries, and likelihood of being mistaken for garbage, it's not really so different from professionally-produced lights. Although I can't recommend using a light with wires duct-taped to battery terminals.

Later I rebuild many of these parts into a 2D cheap plastic light. So far the glass reflector has protected the plastic from melting. The batteries are now 2x2 stacked.

Budget:

$4 4 LifePO4 600 mA cells
$6 1x 20W halogen
$1 1x solar light
$1 Marginal duct tape and paper

$12!

AnAppleSnail said:

20W halogen with about 20 minute runtime
4 LifePO4 600 mA cells

Click to expand...

Does this 20w x 1/3h = 7 w-h of energy correlate well with the battery specs? Your experiment provides data on apparent battery capacity vs. discharge rate vs. battery technology.
Apparently the nominal cell voltage is 3.3v
http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery
which gives a 1.5A drain.

I get
runtime in hours = -0.744(discharge amps) + 1.45
just using these two points and assuming this is a straight line function [doubtful].

wow, that's as ugly as some of my first lights way back when I started here:naughty:,

but ugly is good:thumbsup:, it just means your not afriad to GET IT DONE and see if it will work or not and this defiantly works.

xul said:

Does this 20w x 1/3h = 7 w-h of energy correlate well with the battery specs? Your experiment provides data on apparent battery capacity vs. discharge rate vs. battery technology.
Apparently the nominal cell voltage is 3.3v
http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery
which gives a 1.5A drain.

I get
runtime in hours = -0.744(discharge amps) + 1.45
just using these two points and assuming this is a straight line function [doubtful].

Click to expand...

I'm thinking that assuming the voltage (and therefore current) doesn't drop is a good enough margin on LiFePO4s to protect them from low-voltage cutout. With the bulb voltage I'm not sure that the difference between 12.8v and 11.2v will be visible enough for me in short bursts through the working day, so I just plan on recharging daily or after 20 minutes of use. Also, all these parts are now in a 2-D-cell rayovac flashlight from Wal-Mart, bringing the total cost up to about $15.

I have a new rig: A 4-cell MagnumStar bulb in a 2xAA PIR light, with 2 AA-size LiFePO4s. It's nice and bright, and I plan to compare it to the Streamlight Scorpion I have at work. The AA-size LiFePO4s weren't on clearance, so I've blown about $15 on this setup as well. This one should last longer than the 4.8v Rayovac bulb driven to 8.4v on 2x 18650 in a mag lite. That had niiiiiice throw, though.

Dude you have a great sense of humor, I saw that pic after crusing all the "serious" discussion here and cracked up, I was hoping to find some thread here where the more radical mods have been done.

For example I took a Makita 18 Volt Flash Light and soldered a 12 volt halogen socket to the reflector and made myself a 50 watt portable, talk about freaking HOT the thing smokes in about 20 seconds, so I drilled cooling holes on one side and put a microprocessor cooling fan on the other.

If nothing else it's intimidating, I love to light up suspicious characters who might think of wandering to close to our house.

Minimal 1W halogen light:

You need:
-a 4.5V battery
-a bulb with the right base (I don't know what it's called) and matching voltage

many 6V halogen bulbs out of bicycle headlamps work, for the pictures I used a 3.7V 0.3A rated bulb.






I actually did use this a lot as a kid for night-time reading.
If you try hard enough and have a proper battery with stiff contacts you can squeeze the bulb in between the contacts in a way that won't let it fall out in any position. The battery I used here didn't work that well.

SF G2 for size reference.