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 with a zinc carbon battery. That would be over 600 hours with an alkaline battery).
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 5109LSH15 (old model number 5109LSH7 or 5109LS) costs under $5 if you shop around. This is a great long run time flashlight to have even if you don’t do the modification.
Where to buy:
I like this flashlight because as is it has a long run time before the battery needs to be replaced. 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 (original design. the new design has one high power LED) 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.
Note: See the last step for the modification for the current version of this flashlight.
Here is a data sheet for a straw hat LED:
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:
Either one will be good to have in an extended power outage.