Easier Flashlight Mod Increases Run Time 3.6X

We are going to take a long run time flashlight (65 hours) and turn it into a longer run time flashlight (Update:  The title of this Instructable says 3.6x run time but actual run time ended up being over 360 hours).

Yes it is another long run time flashlight hack. This one is easier than my other one. All you need a resistor, a soldering iron and this flashlight.

This Eveready flashlight (model number 5109LSH7 or 5109LS) costs $4.97 at Lowes:

(This is a great long run time flashlight to have even if you don’t do the modification.)

 

Where to buy:

http://www.lowes.com/pd_355538-346-5109LSH7_0__?productId=3413164&Ntt=flaslight&Ns=p_product_price|0
 

I just picked up another one at my local Lowes. I like this flashlight because as is it has a long run time before the battery needs to be replaced (65 hours). It is bright. It is cheap and it is easy to hack. You can do this hack in 10 or 15 minutes and most of that time will be waiting for your soldering iron to heat up.

The only thing about this flashlight that is less than optimum is that the 3 LEDS have a little too much current going through them. The LEDS appear to be “straw hat” type (20 milliamp) LEDS. Each LED has about 60 milliamps running through it.

Here is a data sheet for a straw hat LED:

 

http://lighthouseleds.com/downloads/dl/file/id/113/5mm_straw_hat_led_cool_white_datasheet.pdf

The LEDS in this flashlight may be specially made to handle more current but in case they are not, this modification will bring the current down to a level that will insure tens of thousands of hours of LED life.

I chose to add a 56 ohm resistor to the circuit so each LED runs at about 16.5 milliamps. This will increase the run time by 3.6 times.

The other step by step instructable to make a long run time flashlight is here:

http://www.instructables.com/id/20-Cent-Upgrade-350-Flashlight-500-Hour-Run-/?ALLSTEPS
 

Either one will be good to have in an extended power outage.

Step 1: Un-solder

You will need to unscrew the black ring that hold the clear plastic cover on the front of the flashlight. Then remove the assembly shown in the picture above. Install the battery and re-assemble the flashlight. Test the flashlight to make sure it works. Remove the rind and assembly shown in the picture above. Un-solder one of the two red wires from it’s metal contact. I chose the one on the left.

Comments

[Clubmike]

ok, I did this, it worked great in fact it is still working. I soldered a 100 ohm resistor in the flashlight on Feb 5 and turned on the flashlight. It is still on and it is March 30. I can still read my calender with it and see down my back stairs to let my dog out at night. In an emergency situation this is exactly what I need. The question is how long will it last?????

[luxstar]

Thank You Clubmike.

When your battery finally does run down you can more than double the run time by replacing the junky carbon battery that came with the flashlight with an alkaline.

[fretted]

Ok i'm going to give this a shot i have to get some batteries but i have some of these flashlights laying about can't hurt to give it a shot thanks for this great idea you made it easy for me to understand and teach to my kids too .....

[luxstar]

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[luxstar]

(removed by author or community request)