AA Flashlights - "Cockroach" / "Vampire" / "Drain-me-till-I'm-empty"

noname tactical

Not exactly a cheap option, but the Peak LED Solutions El Capitan would be an excellent cockroach/vampire light if you had it configured as a low output, no QTC light.

It doesn’t get much tougher than Peak’s lights and as far as being a battery scavenger, my Eiger AAA configured at level 1 beat even the mighty Fenix E01 on operating on seemingly dead cells, I’d imagine the AA El Capitan at a similar drive level would be no different.

The TG06S finally ate the last few useful electrons from it's ancient (2/2005) Kodak Photolife alkaleak. It's been starting on L for about six weeks or so. The past week L has dimmed & begun flickering after about two minutes run time, eventually becoming nearly useless unless in a completely dark space. Last night it shut down completely. The cell tested 0.807v on a DMM immediately upon removal.

slmjim

Usually a good 2×AA (or 2×AAA) light will wring more juice out of the weaker cell first, unless perfectly “balanced”. Luxpro, Sofirn, got too few that actually run down too far; the light seems to go mental first, then completely boembs out at about 2V total.

you do have to watch, as lightbringer suggested, that as batteries deplete to zero, you make sure they are not leaking

because doing that, running them to zero, is the exact thing that causes the cell case to corrode through, and start leaking crud out

do that - and a flashlight can be completely killed in a week, for half a dozen different problems.

just saying - vampire usage sounds fun but it has risks

clocks are vulnerable to this too, if you have say 20 clocks on a wall with only some of them running
the problem is that if one quits, you may not even notice til a year later then the whole thing is corroded

A member here approached me about making a low output, long runtime boost driver to fit the Convoy T2 (aka Manta Ray S1, also available as a host at Kaidomain). Target output was ~1 lumen. No mode switching. Currently 17mm but could be made to be 15mm or about any size.

I went through a couple iterations and ended up creating one that ran an XM-L2 at 2.5mA for ~0.7 lumen for 98 hours on a 900 mAh AAA Eneloop Pro. So on a AA battery, it should run for 12+ days. It runs down to ~0.7 V.

Current is set with a single resistor. Current output could easily be set higher or lower as desired.

Oshpark link. BOM:

  • TLV61220 Boost IC
  • Inductor, 1210 footprint (I used a 10uH but 4.7uH should work as well; look for lower DC resistances)
  • 2x 0603 or 0805 capacitors with 10 uF (pretty much any 10uF cap should be fine)
  • 1x 0603 or 0805 current set resistor (resistance = 0.5V / desired amps, so for 3mA: 0.5 / 0.003 = 167 Ohms)
  • Spring and wires

That sounds really interesting. Depending on cost I would be interested in a couple. Maybe at your tested output and maybe something a little higher like 3-5lm. Is this a constant current driver or PWM? What is the input voltage range (ie: is it adaptable to 2AA)?

  • Constant current (though technically due to the inductor there’s a high frequency ripple… but that’s how boost drivers work).
  • 3-5 lm isn’t a problem, though I need to see which of these drivers would be most efficient at that output. While the ZXLD381 didn’t do great for super-low current, 3-5 lm might be in it’s sweet spot
  • Re: 2AA… in short: shouldn’t be a problem. Long version: the TLV61220 is rated for 0.7 - 5.5V. It has a 0.5V feedback, so if a LED is dropping 2.5V at the preset current target, the boost driver will put out 3.0V (2.5V for the LED and 0.5V for the feedback). If the input voltage exceeds what is needed to hit the current target, I think the TLV61220 will probably go into pass-through. In which case, it might be a touch brighter than anticipated until the battery voltage falls a little bit. With NiMH (2AA ~= 2.4V) this should be a non-issue. With 2 fresh alkalines and a very low current, it might start out just a touch higher than it needs. I can test this out more.
  • Cost: partially depends on how many I make. For the TLV61220 circuit (the better option for really low output) PCB + components are around $2.50 in materials (plus Mouser $3.49 shipping). I would charge actual shipping amount and next to nothing for assembly. For the ZXLD381 (good for currents in the 6.5 - 20mA range), I already have PCBs and components on hand… cost would be like $2 plus actual shipping.

Is 0.7lm the lowest stable output achievable?

Nope! I measured 0.7lm at 2.5mA to the LED. I could drop that down as low as 0.1mA (anything below that and efficiency would likely drop considerably). So even if you wanted 0.1lm, that should be well within reason.

This is great news :wink:
I may be interested 2x17mm and at least 2x15mm, in case you can ship them internationally.
Would it be “good to use” with other leds too? (ex: Luxeon V2)

Thanks for your work :wink:

Yup, any 3V LED should work well.

I ship internationally. The first batch went overseas. But unfortunately the cost is high (around $14 usually). Domestic shipping is around $3.50.

Great :wink:
Hum, I know it is a bit more expensive, I had to pay that when I ordered from MTN, but I don’t mind!
So, in case you accept my “order” (whenever you can make and ship them), I would definitely get 2x17mm and 2x15mm! :+1:

Hmmm tempting, although I have no suitable hosts atm and shipping is a bit pricey. Maybe if there were a lot of UK/EU demand we could do a group buy and have one person this side of the pond re-ship them?

Yeah count me in for a couple! Maybe 3-4 unless you need more to help fill a quantity.

you have to be careful of one thing: alkalines are much more likely and fast to leak when completely discharged

if you let it run down, and then forget for some reason it is sitting there discharged, it might make a huge mess…

wle

Alright, looks like there’s a bit of interest. So I’ll establish some pricing and get a list going. After gathering a list for a few days, I’ll order the parts to assemble however many I get on the list. I’ll try to keep this post updated.

Pricing: $4 per driver including spring and wires (TLV61220 version) or $3 (ZXLD381 version)
Shipping: $3.50 for US, $14 for International

When making your request, please specify:

  • Driver size (15mm or 17mm… or if there’s another you’d like)
  • Desired LED current and/or lumen output (I’ll try to guess about how much mA it will take to get the desire lumen output)
  • Special considerations (such as if you want to use 2AA… I will make sure to test this)

Request List (as of 2020-05-18 10:44 AM CDT):

  • MascaratumB: 2×17mm and 2×15mm, specs here
  • buck91: 2 0.5-1 lumen and 2 in the 3-5 lumen range (all 17mm for T2)

Sweet! Thanks again :wink:

To specify the order:

  • All to use with 1 x AA/Ni-MH batteries

- 1 x 17mm x TLV61220 version (0.3-0.5 lumens)

  • 1 x 17mm x ZXLD381 version (5 lumens)

- 1 x 15mm x TLV61220 version (0.3-0.5 lumens)

  • 1 x 15mm x ZXLD381 version (5 lumens)

Are these values (lumens for the specified driver) reasonable?

Please do so I can see if I can source the parts and attempt to build myself or if I’m better off ordering from you!

I just added the BOM to Post 72. It’s a pretty easy assembly and the only specific item to locate is the boost IC which is widely available.

Also… bump in case there is any more interest out there