AA Vampire

Hi,

I have a large source of partially exhausted AA's and rather than just bin them I'd like to use them up in a single AA light.
So.. I am looking for ideas for a single AA, two mode light, low and a high (any levels will be ok) that can use up the remaining energy in these cells. Most are carbon but some alkaline. The light can be clicky or twisty, no preference, any build. Preferably water resistance, tail standing capable if possible.

I'm not expecting miracles on brightness levels and will accept most kinds of beam, floody whatever, so long as its reasonable clean.

I assume it needs to be direct drive rather than PWM to leech that remaining power?
I know about "joule thief" designs but it needs to be a holdable proper built light I can hand to a user.
Cost is not a big factor.

Thoughts?

The issue you're going to run into is that typical LED's (which are really diodes) have very specific voltage requirements and require (usaully) ~3.0v to run direct drive, so a fully charged AA won't even light one up.

You're going to need a boost circuit of some sort and not much out there beats a Joule Thief and..... thay can be built with SMD components and fit into a standard P60 drop in. The catch is that the SMD version will typically only get you down to about .8v whereas I've seen the tried and true wound coil JT get as low as .5v when running and start the circuit when as low as .8v

If I were you, I'd look up CPF member Wquiles, he has a ready to go SMD JT circuit that's small enough to fit into a P60. Catch is that it will be single mode only and pretty much a DIY project, but... once built, any P60 host will net you a solid light.

But, as you noted, you're looking for more of a proper light and if a ready made light is what you want, it's going to come down to the boost circuit in the light itself... I've had good results with the 4 sevens Quark on Moonlight mode and the zebra light SC51. I think both of them get down to at least .8v

Most of the specs are on the websites and should give you some idea of the minumum voltage needed to fire the light itself.

Hope that helps a bit.
D

How about a Peak El Cap (or Logan 17500) QTC ?

IIRC, the Kilimanjaro would go rather low, but are long out-of-production....

Ok, my understanding grew just a little. It seems to go direct drive, technically I'd need a 2 x AA but as you suggest the voltage drops hinder it working. Thanks for the lead. It seems what I thought was an easy ask is not so easy after all.!

Darvis said:

But, as you noted, you're looking for more of a proper light and if a ready made light is what you want, it's going to come down to the boost circuit in the light itself... I've had good results with the 4 sevens Quark on Moonlight mode and the zebra light SC51. I think both of them get down to at least .8v

Click to expand...

+1 on these lights.

I got the equivalent of 600-700 hrs from these lights on a 9V (well, actually only had the patience to test one of the AAAAs out of it).

Don't think you want to go much below 0.8V, as I understand you run a much greater risk of leaking.... and definitely don't do vampire runs with a multi-cell - you will definitely cause a leak from reverse charging (don't ask how I know).

As reppans says, if you run alkaline batteries right down to a very low charge, some of them WILL leak and probably damage your light. Not a good situation if you have spent money to buy a decent light.

For your circumstances consider an el-cheapo light from evilBay. I've had good results with quite depleted batteries with item # 140571826345 Not a "good, quality" light by any stretch of the imagination, but for $US 2.28 including shipping to Oz I don't expect much more than usable light. If a battery leaks and ruins one of these you aren't going to be too upset. I've bought dozens as give-away lights and they have been pretty reliable (only had one DOA that I couldn't fix due to a faulty switch, and if I felt like it I might have been able to fix that one too). These are one of my best single AA battery vampires, better than a lot of much more expensive lights.

I think I remember 4seven mini AA is a good battery vampire.

You should check out Will's Joule Thief Boards. He can send you just the board or send it to Nailbender to make a drop in from it. It's whole purpose is to drain the crap out of cells. http://www.atdms.com/battery_vampires.html

Nite Ize used to make a 3-LED Mini-Mag drop-in that had an amazing ability to deplete a single AA cell that even a toroid Joule Thief won't light up with. Drop one of those into a Mini-Mag with a dummy cell and you'll have an awesome battery drainer. If the battery leaks then just move the drop-in and spacer to another MM and away you go.

PCC said:

Nite Ize used to make a 3-LED Mini-Mag drop-in that had an amazing ability to deplete a single AA cell that even a toroid Joule Thief won't light up with.

Click to expand...

This is what I have too. I've made Joule Thieves with toroids and Zetec 380's and this is probably one of the easiest methods. Keep a bottle of vinegar on though.