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Thread: Buying my first unprotected cells...am I doing this right? (Long read, sorry)

  1. #1
    Flashaholic
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    Default Buying my first unprotected cells...am I doing this right? (Long read, sorry)

    ETA: it's long, so I highlighted questions in blue. Any tips appreciated.

    I recently picked up five Convoy s2+ hosts for different projects and now need 18650s for them. I have about 25 LIons on hand, but all have been protected cells (AW, Keeppower, EagleTac, etc.), except for 2 AW IMR 16340s. The prospect of picking up 5 protected 18650s at the same time (~$100), for lights I won't use often, made me look into unprotected cells. A lot has changed since the last time I read about LIon cells...

    In addition, I have a few lights (Convoy S2+, old Jetbeam mkIIx, Fenix PD35), where the ever-lengthening 18650s are realllly compressing the springs. On some lights, the springs must be basically flat to accommodate the battery, and I imagine that strain can't be great for them. Anyone else having that problem and thinking it's bad for springs?

    From researching here, it looks like Panasonic's NCR18650GA, Samsung INR18650-30q, and Sony VTC6 are all good cells.Would those be good starters? I guess what worries me is that different sources don't agree on the chemistry of these cells and some sources just say "hybrid/other." Which makes me feel like I don't know what I'm doing or how safe they really are. Can anyone confirm the chemistry of any of those cells?

    Are these all generally safe to use in single-cell lights? The crux of the advice from threads here seems to be "just don't ever let them sit too long or run them too low." Which leads me to another question: some lights have low-V protection and others don't. Is there an easy way to be sure which lights have it and which have been cutting off due to the my cell PCBs? With protected cells for all these years, I don't really know which are which. Some lights dim over time, some strobe, some (like all my Malkoff's) maintain steady brightness and then suddenly die....and I'm not sure what's due to cell and what's do to light engine. Reading here has made me want to make up a battery tester for voltage under load (with a simple resistor that approximates the light). I also want to do run tests where the light is on tailcap ammeter and a voltmeter and I can chart voltage vs time for the light to learn each light's performance over the discharge range, and most importantly, the end-behavior. Because it seems knowing your light's end-behavior (based on cell voltage) is the key to knowing your cell isn't being over-discharged. Is knowing your voltage-time discharge curve the key to making sure you don't over-drain your batteries?

    All that said...any advice on cells? Trusted places to buy? How to run unprotecteds safely, without having done brightness vs voltage tests on each light? And then, does anyone have any recommended resources for learning more about LEDs, Vf, regulation, buck/boost, 7135s, MCUs, MOSFET, up-to-date LIon chemistry, etc? All things I've read about here, but mostly in passing, so I'm half-familiar, but don't really feel like I understand. Threads from the electronics masters here (you know who you are) have been uber helpful -- thank you for sharing the wealth of knowledge that's here. If anyone has any input on any little piece of the above...much appreciated!
    Last edited by tomcat017; 09-13-2017 at 12:01 PM.

  2. #2
    Flashaholic* ChrisGarrett's Avatar
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    Default Re: Buying my first unprotected cells...am I doing this right? (Long read, sorry)

    I've got an S2, an S2+ and a modified S2+ with LD-2 driver and Triple XP-L HI LEDs. The latter direct driving on turbo at 6A measured. I only use unprotected cells in them, but I check my voltages a lot. Plus, they have step downs, so I know when I'm getting low.

    Any of those 18650s will work with the S2+, even a modified one, but running typical 2.8A Convoy drivers, you can get by with the Pannie NCR-Bs, if the price is right.

    Chris
    Last edited by ChrisGarrett; 08-31-2017 at 09:21 PM.
    Convoy: S2, S2+, M1, M2, Fenix: P1D, PD32, HL30, ET: D25C Ti, SF: 6P, ZL: SC-600, Klarus: P2A, Jetbeam: BA-20, Icon: Rogue 1, L3: L10, Xeno: E03, ShiningBeam: I-Mini, Olight: i3s, SWM: D40A, M11R, V11R, Maglite: 6Ds, MMs, Solitaires, LaCrosse BC-700, Maha C-9000, XTAR VP2, MP1S, XP1, MC1+, WP2 II, NiteCore i4, v2.

  3. #3
    Flashaholic
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    Default Re: Buying my first unprotected cells...am I doing this right? (Long read, sorry)

    TY CG. Bump for any additional advice.

  4. #4
    Flashaholic mightysparrow's Avatar
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    Default Re: Buying my first unprotected cells...am I doing this right? (Long read, sorry)

    I recently bought my first unprotected cells. I use the Panasonic/Sanyo NCR18650GA unprotected cells from a reputable dealer, and use them in flashlights with over-discharge protection circuits in them. I charge them using Xtar chargers. However, I also check their voltage periodically with an inexpensive multi-meter. I check the voltage of the cells I have in storage, also, to make sure I don't let them discharge too low.

    My advice: get yourself a reliable multi-meter and use it with quality cells and a quality charger.

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