My proud contribution - a way to make a battery powered reusable glow stick actually *useful*.
I like to leave something lit on my vehicle when hiking near sunset (which I do a lot for photography) so I can find the truck in the dark. Also useful for finding your truck in campgrounds. Ideally this would be one of those LED glow sticks. And of course they are small so you can take a few with you if night hiking to visually mark an important way point for your return.
Unfortunately I've found the "dumb" sticks burn very bright for the first few hours rapidly draining the expensive watch batteries and then burn dim for a total of only maybe 8 hours of useful brightness. This is because these sticks just short the LED to the batteries.
There are "smart" sticks that appear to do a little bit of current regulation and have blinking modes. Sadly these mostly seem to have an "auto-off" battery saver feature as well which defeats the whole purpose of being a marker.
My great insight is using a special battery with "dumb" sticks to dramatically increase burn time.
First the sticks - I used the Life+Gear "Reusable Glow Stick" that is *twist* to turn on. These are "dumb" sticks that the twisting motion just causes a direct contact between LED and batteries. Do not get the "fancier" sticks from the same manufacturer that have blinking modes, flash lights or any other sort of smarts. The "dumb" sticks are sold at Target for like $1.49 or something.
Now these sticks will burn insanely bright for the first hour or so as they rapidly drain their batteries. As the battery drains its voltage lowers and the forward current of the LED also drops reducing brightness and extending the burn time. You might get 15 hours from this if you are lucky. The whole problem is no current regulation for the LED, it is just shorting the battery. Thus the LED current is like 75 to 150 mA initially depending on the color. It really only needs to be about 5 to 10 mA for adequate brightness.
The solution? Use hearing aid batteries instead (called Zinc Air batteries). These naturally current limit as the current is limited by transport of air into the battery case (these batteries have little holes in them covered by a sticker that you remove when you want to use them). They are also much higher energy density than most batteries precisely because they use air from the atmosphere as part of the chemical reaction.
How much better do they work? I get a burn time of 7 to 8 *days* using hearing aid batteries. That's continuous discharge, never turning it off. So around 150 hours of burn time.
The trade off? Once you pull the sticker off of a hearing aid battery it must be used within just a few weeks. So you use one set of batteries per camping trip, but you they are so efficient you could leave them on the whole trip - even during the day.
Here is a link to the glow sticks I use:
http://www.lifegear.com/glow-sticks-1/lg11-60221-mt4
The proper hearing aid batteries to use are 675. That is the same size as the 357 battery except it uses Zinc Air electrolyte.
I'm probably the only one who thinks this is as cool as it is... But seriously, if you want a good cheap and featherweight light marker that will last days and is shelf stable for a long time until you pull the stickers this is the cheapest and most reliable solution I know of.
...)
