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  1. L

    Reviving old NiMH cells using science?

    I came across this scientific paper: https://www.mdpi.com/2313-0105/2/1/3/htm (full text and PDF are free, just click the link). In the last section, it states Does anyone have any information about this? I couldn't retreive the original paper that describes the 33% SOC method, however I...
  2. L

    Highest capacity cells in each size.

    I'd like to make a list of the approximate maximum capacity of each form factor of currently available cylindrical cells. This would firstly help to guide new users so they don't fall into the trap of buying Chinese cells with completely fictitious capacity numbers. Secondly it will be useful...
  3. L

    Looking for raw voltage vs time data for an NiMH charge cycle.

    I'm curious as to how -dV/dt detection may be implemented in practice. Specifically, what kind of algorithm would work best at detecting the peak. To this end, I've been looking for a plot of dV/dt (the first derivative of voltage with respect to time) for a typical NiMH charge cycle...
  4. L

    Five technical questions about LEDs in general

    Hope this is the right subforum. I have some generic questions about LEDs in general. Here they are in no particular order: 1. How much of the input power to an LED is lost as heat? For example, take a Cree XM-L running with 10W input power (3.2V x 3.0A). How many watts are actually dissipated...
  5. L

    Reviving Energiser AA Ni-MH cells with unknown history and strange behaviour

    I found these batteries in an old (and I mean old!) flashlight. It's actually an emergency light with a plug-in charger that presumably keeps the batteries charged and switches it on automatically when there's a power cut. Basically, they seem to have the highest internal resistance I've ever...
  6. L

    3 quick general questions about my new WF-502B

    Today I picked up my second XM-L powered light - a WF-502B, and after taking it apart it seems there's room for some good TLC (thinks lik small metal shards from machining, small pieces of dirt on the glass and the dome, stiff threads etc.) Since this is only my second flashlight, I was hoping...
  7. L

    What ar the most efficient and (separately) cheapest LEDs available at the moment?

    By efficiency, I mean lumens per watt for a high power LED (the kind used for flashlights) Last time I checked itwas the CREE XM-L U2 - but has anything better been released into the market? Secondly, which is the most cost-efficient high-power LED in terms of lumens per dollar (or euro)? I...
  8. L

    Odd XM-L failure upon startup when overdriven to 4A (in-rush current?)

    I recently bought a CREE XM-L T6 with the intention being to do some maximum power testing (i.e. see how much it could take before something broke). Setup: The LED came pre-soldered to a 16mm round board and I stuck the board to a Xigmatek Dark Knight (pics of heatsink here) with thermal...
  9. L

    Odd drastic loss of light output after a month of use

    I have a cheap DX-style light. It runs on one 18650 cell and uses a P60-size dropin with a CREE XM-L emitter (pic) It used to draw 1.7A on high, 0.7A on medium, and 0.05A on low. A while ago, it started to randomly dim and flicker, and then go back to full power all on its own. It would do...

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