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9 LED flashlight batteries question

Discussion in 'Electronic Basics' started by Ivan Vegvary, May 30, 2013.

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  1. Ivan Vegvary

    Ivan Vegvary Guest

    Have a sh** load of the above. Get them free when shopping at Harbor Freight.
    Lately, when batteries fail, I started checking with a voltmeter. Turns out that two of the three batteries always register circa 1.4 volts, while the third is about 0.6± volts. Naturally, I started keeping the two highervoltage cells instead of trashing all three. Is this typical? Have I been needlessly wasting batteries this last 50 years? Never occurred to me tocheck voltages. BTW, these are all AAA cells.

    Ivan Vegvary
     
  2. Maybe just cheap batteries. (?)
    When you replace with new 'good' batteries do the cells discharge at
    the same rate?

    George H.
     
  3. Bill Bowden

    Bill Bowden Guest

    I usually check batteries by measuring short circuit current with a
    DMM on the 10 amp range. Good alkalines read about 5 amps,
    (D,C,AA,AAA) are all about the same. Carbon zincs read about half as
    much, or 2 amps. Voltage is misleading, the acid test is short circuit
    current.

    -Bill
     
  4. Nobody

    Nobody Guest

    Weird.

    Normally, an unloaded battery reads close to its nominal voltage
    regardless of whether it's brand new or completely flat. The difference is
    in the internal resistance, i.e. how quickly the voltage drops as the
    current drawn increases.
     
  5. Phil Allison

    Phil Allison Guest

    "Ivan Vegvary"

    Have a sh** load of the above. Get them free when shopping at Harbor
    Freight.
    Lately, when batteries fail, I started checking with a voltmeter. Turns out
    that two of the three batteries always register circa 1.4 volts, while the
    third is about 0.6± volts. Naturally, I started keeping the two higher
    voltage cells instead of trashing all three. Is this typical?

    ** Yes.

    Very unlikely for three cells to be identical - one cell is likely to be the
    weakest.

    The effect seems to be worse when the load current is high - as in your
    example.

    Saw this over and over with groups of 4 x alkaline AAs used in RC receivers.

    Why I changed to using NiCds.


    ..... Phil
     
  6. Phil Allison

    Phil Allison Guest

    "Nobody"

    " Lately, when batteries fail, I started checking with a voltmeter. Turns
    out that two of the three batteries always register circa 1.4 volts,
    while the third is about 0.6± volts."
    ** Not all all.

    3.4 volts is where the LED torch begins to fade out - under load it will be
    much less.

    ** Absolute GARBAGE !!!


    ** That is a separate fact.

    Cell voltage does relate to remaining capacity fairly well and very well if
    the cell is under its normal load.

    Not true for rechargeable types though.



    .... Phil
     
  7. Jamie

    Jamie Guest

    Really? sounds a little bogus to me.. Since i've seen a good many
    cells exhibit low voltage after drain.

    If you are referring to rechargeable's, that could be a different story.

    Jamie
     
  8. I don't know. IN the old days "batteries not icluded" wsa pretty normal,
    but most things I've bought in recent years did have batteries when
    applicable. And I find the batteries generally fairly good. Not
    noticeably bad.

    I don't know where the pricing comes from. I keep buying LED flashlights
    (torches in some countries), and they come with batteries. And then it
    often seems to make sense to buy a new one when the batteries do die out
    An exaggeration, but I keep buying the LED flashlights because they keep
    adding LEDs to them, making them brighter.

    FOr that matter, I've needed button cells to replace worn out button cells
    in various things, and for those that need the size, it's cheaper to buy a
    99cent or $1.49 laser pointer for the batteries than buy the button cells
    separately. Yes, you can get the cells cheap in some circles, but
    generally not as handy as where the laser pointers get sold.

    Ironically, the one LED flashlight that I care most about is faulty. I
    have a 2AA Maglite, and a few years back got an LED replacement bulb,
    which worked fine, but now has gotten flakey. I'm not sure if it's the
    contacts, the LED module, or the Maglite. Ironic since the Maglite wasn't
    cheap, and neither was the LED replacement, but the cheap LED flashlights
    generally are fine.

    Michael
     
  9. Actually my need for button cells is for that kitchen timer I have lying
    her waiting for a battery. I've bought laser pointers for the button
    cells for those kitchen timers before, I think I got an analog battery
    operated clock going with a button cell from a laser pointer too.

    I also have a battery powered pocket watch that needs a new battery. WHen
    I finally got the back cover off, I discovered it used "button cells" like
    you find in computers, CR2026 or whatever, for the built in LED
    flashlight, which still works fine (it used a red LED, so I never used it
    that much). But the clock runs off a separate battery, and that one is
    smaller, I think smaller than the laser pointer batteries. SO that too
    sits opened, waiting for me to get around to looking for a suitable
    battery.

    Michael
     
  10. Bob Masta

    Bob Masta Guest

    For certain items like kitchen timers, clocks, and
    calculators I often use a trick: Old 9V batteries from
    smoke detectors, etc, still have a lot of juice left when
    they are no longer useful in their original application (at
    least compared to the low-voltage trickle needed by LCD
    display devices). I build a tiny voltage regulator using a
    couple of NPNs and LEDs (forward biased through a high R to
    serve as a sharp-cutoff Vref). The whole works can be
    soldered together on top of a 9V battery clip, though I've
    also made tiny PCBs from scraps.

    The result is that the 9V battery typically powers the
    device for a year or 2, at least, before it can't maintain
    the 3V needed for the device. By then I've usually
    collected plenty more 9V batteries. Snap the old one out
    and the new one in!

    Of course, the Frankenstein timer/clock/whatever with a
    hulking 9V battery strapped to it is not likely to appeal to
    anyone with delicate sensitivities or fine aesthetic sense
    (or maybe *any* aesthetic sense!), but I get a kick out of
    the whole idea of running it "for free".

    Best regards,


    Bob Masta

    DAQARTA v7.21
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Sound Level Meter
    Frequency Counter, Pitch Track, Pitch-to-MIDI
    FREE Signal Generator, DaqMusic generator
    Science with your sound card!
     
  11. I once bought a nice LCD clock for a couple of dollars, it was nice
    because the readout was larger than what I'd found at that price level.
    And when the button cell wore out, I didn't even bother looking for a
    button cell, I just soldered in an AA battery, hanging it off the back.
    The AA battery does last forever, I can't remember when I soldered in the
    first one, but it was at least a decade ago, and I've replaced it once,
    and it keeps on ticking.

    I guess I wanted the kitchen timer to be more portable.

    And yes, I do change the smoke detectors after a year or so, and thus the
    "old" batteries get used for something else, that isn't as important, so
    the smoke detectors run fine but the batteries aren't wasted.

    Michael
     
  12. Jamie

    Jamie Guest

    Ah, so that's you I see out at night rooming the streets?

    Jamie
     
  13. Jamie

    Jamie Guest

    We have junk stores around here too. I have a package of 9 i think it
    was of CR2032's for under 2 bucks. And they also have a variety pack of
    coin cells for that price, too.

    The CR2032's work great for my key fob that seems to like eating cells
    for my Jeep. It has a keyless entry and ignition system.

    Jamie
     
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