I had an email in my inbox this morning directing me to an instructables.com post that takes a $5 Eveready flashlight and modifies it so that it runs for over 360 hours.

In brief, the poster (luxstar), modified an Eveready 5109LS LED flashlight by adding a 56-Ohm resistor. The flashlight before modification had a 25 lumen output and a 64 hour runtime.  On its own, unmodified, that is pretty impressive for a $5 flashlight.

While doing a web search for additional information, I found a $.99 eBook The Amazing 2000-Hour Flashlight by Ron Brown that had a picture of the Eveready 5109SL on the cover, so I purchased the book and found that Ron Brown took “luxstar’s” original modification and made his own improvements to make the Eveready run for 2000 hours.  2000 hours is over 5 hours a day for 1 year.



Based on the information I learned from instructables.com and The Amazing 2000 Hour Flashlight, I did my own modifications.  Here is what I did and how it worked out.

I bought my Eveready 5109LS at my local Home Depot for $4.87.  This is NOT a small Everyday Carry Flashlight.  The Eveready 5109LS is a lantern type flashlight that runs on a 6 volt battery.  An Eveready 6 volt Super Heavy Duty Battery is included.  The Eveready 5109SL has 3 LEDs and is rated at 25 lumens.  That is adequate light for camping and is way more than enough light to move about a house at night, find emergency items you need, and do all kinds of tasks.

The flashlight I bought was labeled differently than the stock picture shown above.  It was marked 10X and showed a 130 hour runtime instead of the 5X and 64 hour runtime on the stock picture.

I bought a 5-pack of 100-Ohm 1/2 watt Resistors and a 5-pack of 150-Ohm 1/2-watt Resistors from Radio Shack for $1.49 per 5-pack.  Radio Shack stock numbers are 271-1108 for the 100-Ohm Resistors and 271-1109 for the 150-Ohm Resistors.


The Hack (Modification)

1.  I unscrewed the Black Ring and removed the Lenses Assembly.
2.  Using a pair of wire cutters, I cut the longer Red Wire right in the middle.
3.  Using a pair of wire strippers, I stripped 1/4 inch of coating from the end of each wire.
4.  Using a micro screwdriver that was a little less than 1/16 inch in diameter (you could also use a small drill bit), I wrapped each of the resistor wire leads around the screw driver to form a coil, leaving about 1/4″ uncoiled on each end.
5.  I inserted one of the stripped Red Wires into the coil on one side of the resistor.  Using a pair of needle nose pliers, I crimped the coil making sure I had wire to wire contact.  I repeated the process for the other Red Wire and the other coil of the resistor.
6.  I soldered each crimped coil/stripped Red Wire Connection.

I have average soldering skills and had no problems making these modifications in about 15 minutes.  Here is how the finished lenses assembly looked.

Check out instructibles.com to see the different way luxstar soldered his resistor to the lenses assembly.  His method doesn’t requiring any wiring stripping and may not even require coiling the resistor wire leads.

I showed you the above modifications (cutting and stripping the longer red wire and then coiling the resistor leads) in case you don’t have a soldering iron or don’t trust your soldering skills.  If you don’t want to do any soldering, once you have crimped the wires and resistor leads together, you could use some conductive wire glue to make sure your connections are solid.  Conductive wire glue is available at Radio Shack, for about $5.


Output Results

I did two modifications.  One with a 100-Ohm Resistor and one with a 150-Ohm Resistor.  My plan is to use these long-running flashlights as home emergency flashlights.  My aim is to maximize runtime by having just enough light to get around the house in the dark, find any emergency gear I need, and maybe read a good book before bed.  I don’t need 25 lumens for those tasks, 5 – 10 lumens is plenty (1 – 3 lumens is plenty to read a book).

Each of the three LEDs in the Eveready 5109SL needs about 20 milliamps to be at full 25 lumens power.  The 100-Ohm modification cut the total milliamps to 50.  Mathematically, that would cut 17% of the lumens so we should still have 20 – 21 lumens.   Based on my visual comparison in a dark room, I’d say that was about right but 20 lumens was still too much light for my purpose.

The second modification was with the 150-Ohm Resistor.  Based on visual comparison, it produces about 15 lumens of light, which is just about right.


Run Time Results

Runtime is determined by how long it takes a flashlight to reach 10% of its initial output.  If I start with a 15 lumen flashlight, turn it on and start a timer, runtime ends when the output reaches 1.5 lumens or 10% of the initial output.  15 lumens initial output is good for me since I can still wander a house and read a book on 1.5 lumens.

I’m going to give you some results based on testing done by Ron Brown for his eBook The Amazing 2000-Hour Flashlight.  His results were based on how long the flashlight could run before it output less than 2 lumens.  I’ve provided information several times from Ron Brown’s eBook.  It is an interesting read and definitely worth the cost of a large $.99 candy bar. It is in kindle format and can be read on your kindle, cell phone or computer.

The unmodified Eveready 5109SL just as it comes from the store, 250 hour runtime with output of 2 lumens or more.  That is equal to over 4 hours a day for 2 months.  That is a crazy good $5 flashlight.

The Eveready 5109SL with the “luxstar” 56-Ohm modification, 500 hour runtime with output of 2 lumens or more.  That is equal to over 4 hours a day for 4 months.  That is a crazy good $5 flashlight with a $.30 modification.

The Eveready 5109SL with a 150-Ohm modification, runtime with output of 2 lumens or more, still to be determined.  I have started the test and based on the results from the other modifications, I am confident that this will be a 1000 hour flashlight.  Even running it 24 hours a day, it is going to take 42 days to burn the battery out, I’ll keep you posted.  1000 hour runtime is equal to over 4 hours a day for 8 months.  That is an even crazier good $5 flashlight with a $.30 modification.


Other Modifications

So far we have been using the Super Heavy Duty Battery that comes with the flashlight.  An Alkaline Battery last longer and stores more power than a Super Heavy Duty Battery.  The cheapest 6 volt Alkaline Battery I could find for the flashlight was $6 at Wal-Mart.  A replacement 6 volt Super Heavy Duty Battery is $3 at Wal-Mart.  Will one Alkaline Battery last longer than two Super Heavy Duty Batteries?  I don’t know and I don’t want to take 3 months to see if it does.

If you have read much of my blog, you know I love rechargeable Ni-MH AA batteries.  What if there is an extended emergency and I can’t find a 6 volt replacement battery?  Rayovac makes a 6 volt Battery Adapter to convert 4 D cell batteries into a 6 volt battery.  But didn’t I say that I love AA batteries not D Cells?  Well, I also love the La Crosse BC1000 Alpha Power Battery Charger which comes with 4 adapters that let you use AA batteries in place of D cells.  The Rayovac adapter includes 4 D cells.  Currently $5 shipped.

Four D Cells will give you about 200 hours runtime.  Four AA batteries will give you about 100 hours runtime.  I have several flashlights that have 25 hour runtimes on a single AA battery but each of them cost at least three times as much as the Eveready 5109SL.

Finally, did I ever mention that this crazy $5 flashlight also floats.



Ed Rogers
Copyright “Keep It Simple” 2013. All Rights Reserved.

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