D cell dilemma

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mcgivor
mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
in In the Weeds--Member's Choice #1
My high power Led  flashlight uses 3 D cells, unfortunately the commonly available $0.60 Zinc Carbon cells don't last very long, alkaline ones such as Duracell are expensive in Thailand at $3 each and are marginally better. The rechargeable NiMh or NiCad type don't perform well due to the nominal 1.2v, a loss of 0.9V, this got me thinking about lithium but the cell voltage is too high, but if I was thinking along those lines then others must have done so as well, so I researched and they do exist so I ordered some to evaluate.

Unfortunately they mistakenly sent C type and due to Covid restrictions at the time, I was unable to return them so I simply made an adapter, they are excellent, the light output is constant, as soon as it drops, which is sudden, it's time to recharge. The disposable type gradually drop over time so usually disposed before end of life due to the high demand. The cost was a $26 for 3 so a little over double the Duracell price they last longer and after 3 recharge cycles they will have paid for themselves. 

 
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • kc8adu
    kc8adu Solar Expert Posts: 50 ✭✭✭
    #2
    ok for a flashlight.
    worthless for any kind of radio/communication stuff.
    a few of the 9v are ok.
    this being the ones with 2s li-ion or 3s lifepo4.
    a better solution is a 3d printed adapter with 1 or possibly 2p 26650 li-ion.
    more capacity and lower ir.
    esp a 2p adapter.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,017 ✭✭✭✭✭
    #3
    I would think a better option would be to just get a rechargeable lithium flashlight.

    Not sure what/how these are 1.5 volt lithium rechargeable, but the native lithium cells would be 3.2-3.7 volts, so something 'extra' is going on...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
    The cells lasted 4 months on a charge without dimming of the flashlight, just thought it time to recharge, yes it would probably have been cheaper to replace with a rechargeable plastic flashlight, but I favor the robust design of the machined aluminum, waterproof  one I have.

    Obviously there is  internal  voltage reducing circuitry  involved  to output 1.5V from the lithium cells but so far they have outlasted a set of alkaline cells and probably 3 sets of cheap zinc carbon type. Can't say one way or another how they would work with other loads but would think there would be little difference, one time disposable cells are dinosaurs, just trying to extend the useful life of my trusty workhorse flashlight/weapon.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • kc8adu
    kc8adu Solar Expert Posts: 50 ✭✭✭
    #5
    well since you like the secondary purpose of a maglight i would have run(and do) the 10000mah nimh d cells.
    or the slightly lower capacity low self discharge type.
    the weight enhances the impact performance .
    and the reason the fancy li ion usb cells are worthless in anything rf like radios is due to the rfi produced by the buck converter in each cell.
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