Lithium Ion hold significantly more charge than NiMH?

Discussion in 'Digital Photography' started by void, Nov 21, 2006.

  1. void

    Bucky Guest

    perfect... from manufacturers' point of view! =) expensive and need to
    be replaced
     
    Bucky, Nov 21, 2006
    #21
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  2. void

    Mueen Nawaz Guest

    Less energy? Most Li-ion batteries I've looked at (not many,
    admittedly) are rated at less than 2500 mAh. Finding 2700 mAh NiMH
    batteries is quite trivial.

    --
    Intaxication: Euphoria at getting a tax refund, which lasts until you
    realize it was your money to start with.


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    Mueen Nawaz, Nov 22, 2006
    #22
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  3. void

    Phil Wheeler Guest

    mA-h does not tell the whole story. Time above a
    usable voltage is also important.

    Phil
     
    Phil Wheeler, Nov 22, 2006
    #23
  4. void

    ASAAR Guest

    It's impossible to compare Li-Ion with NiMH if you only have the
    mAh rating, since no Li-Ion batteries supply 1.2 volts. But in many
    cases (as you note) the Li-Ion batteries do provide less energy than
    many people would guess. Here's an example.

    The energy that batteries contain is roughly proportional to the
    battery voltage * mAh, and multiplying them provides the capacity in
    Watt Hours. As dpreview notes*¹, Canon's original 7.4 volt BP-511
    battery had an 8 WattHour rating, and the improved BP-511A, used in
    the G6 and 300D, due to its higher 1390 mAh capacity reaches 10.3
    WattHours. In a weird move, Canon supplies their G7, 350D and the
    new 400D with the smaller NB-2LH battery. It's 1.3 oz. lighter but
    at only 720 mAh and 7.4 volts manages only a 5.3 WattHours. That's
    a mighty poor tradeoff, especially for anyone that routinely carries
    one or more spare NB-2LH batteries.

    Compare this with a set of four 2700 mAh AA batteries, as used in
    Canon's smaller A620/A630, which provide 4 * 1.2 * 2700 == 13
    WattHours. This is 26% more energy than Canon's heftier BP-511A
    provides, and 145% more energy than the NB-2LH.

    http://www.dpreview.com/reviews/canong6/page4.asp
     
    ASAAR, Nov 22, 2006
    #24
  5. void

    Ron Hunter Guest

    Yes, but at twice (or more) the weight. There are a lot of factors to
    evaluate in choosing a battery. Also, cameras are designed to best use
    a certain type of battery, and will usually work better with that
    battery type.
     
    Ron Hunter, Nov 22, 2006
    #25
  6. void

    ASAAR Guest

    Is it really "twice (or more) the weight"? Even if it is, saving
    that extra 1.3 ounces is (as I said) a mighty poor tradeoff for
    getting virtually double the battery life. I'll bet that if Canon
    shaved off another ounce from their Li-Ion battery few would be
    amused. And don't forget, the smaller the battery, the more likely
    it is that the photographer will need to compensate by carrying
    another battery or two, negating the reduced battery size and
    raising the total amount of money sunk into batteries. Saving an
    ounce can make sense for a small P&S, but even lightweight DSLRs
    such as the 350D and 400D will often be used with lenses other than
    the smallest, lightest fixed focal length or kit lenses and other
    "stuff". Canon's decision to cut the battery capacity in half
    brings to mind the familiar "penny wise and pound foolish". <g>
     
    ASAAR, Nov 22, 2006
    #26
  7. void

    Phil Wheeler Guest

    Yeah .. my take, too re the DSLRs. But maybe they
    can sell more batteries that way ;-)

    Phil
     
    Phil Wheeler, Nov 22, 2006
    #27
  8. But LiIon cells are much higher voltage. Energy is volts times
    amp-hours. A 900 mAh LiIon cell at 3.6 V is the same amount of energy
    as a 2700 mAh NiMH cell at 1.2 V. Another way of looking at it: you
    need 3 1.2 V NiMH cells to equal the energy of one LiIon cell if both
    have the same mAh rating.

    As a general rule, LiIon and NiMH actually store about the same amount
    of energy per unit *volume*. LiIon is much better per unit *mass*,
    since they are so much lighter than NiMH (and alkaline).

    Dave
     
    Dave Martindale, Nov 22, 2006
    #28
  9. void

    Mueen Nawaz Guest

    Thanks for the correction - I did not know they had different voltages.
    My old Olympus took both, and so I assumed they had the same voltage.

    --
    As a child my family's menu consisted of two choices: "Take it, or leave
    it."


    /\ /\ /\ /
    / \/ \ u e e n / \/ a w a z anl
     
    Mueen Nawaz, Nov 23, 2006
    #29
  10. The Oly LiIon packs had two cells in parallel. That's why they were a
    pack that slid in diagonally. The camera's regulators were good for
    something like 4V to 9V so it could use 4-5V from four NiMh or the 6-8V
    from 2 paris of LiIon.
     
    Kevin McMurtrie, Nov 23, 2006
    #30
  11. void

    ASAAR Guest

    ??? Are you sure about this? If the Li-Ion cells were connected
    in parallel they wouldn't be providing a voltage in that high 6-8V
    range, but at a lower voltage comparable to what the four NiMH cells
    could provide. Which camera(s) were they? DSLRs?

    One way for cameras to more efficiently use alkaline batteries
    would be to use circuits such as the ones used in Energizer's CHAA
    and CH2AA chargers that use one or two lithium or alkaline AA
    batteries and are used to recharge cell phones in the field.
    Energizer claims "87% typical electronic converter efficiency" and
    says that they can keep providing a 5 volt charging current even
    when the AA cells have dropped to 0.6 volts. The single AA version
    charges at up to a 320ma rate and the two AA version at up to 600ma.
    Circuits such as these would allow cameras to get almost as many
    shots from alkaline cells as from NiMH, where NiMH typically lasts 2
    to 4 times longer than alkaline cells.
     
    ASAAR, Nov 23, 2006
    #31
  12. Four LiIon, two parallel pairs in series, is ~7.6 volts.
    Watts = volts x amps

    An alkaline battery always produces at about 1.5 volts. If you load it
    down to 0.6V with a DC-DC inverter, there is 0.9 volts lost to heat
    inside the battery. That's not very efficient.

    You're talking about buffering alkalines with another storage device.
    Ultra-capacitors can be used to improve the efficiency of alkaline
    batteries but they take up space and cost money. There's little point
    to using alkaline batteries plus ultra-capacitors together unless you're
    over the current capability of NiMH too, which you aren't in a camera.
    Buffering with ultra-capacitors is more for 2-way pagers where the power
    source is a AAA cell, the average power draw is small compared to NiMH
    self-discharge, and the transmitter needs short bursts of several watts.
     
    Kevin McMurtrie, Nov 23, 2006
    #32
  13. void

    ASAAR Guest

    Ok, that makes sense. But two parallel pairs is quite different
    than "two cells in parallel". The only Oly battery I've seen is the
    BLM-1 which is rated at 7.2 volts and as far as I can tell is
    constructed using only two cells. You added "or the 6-8V
    from 2 paris of LiIon" at the end of the paragraph, but it
    conflicted with the earlier "two cells in parallel", hence my "???".

    Obviously. In another recent reply I mentioned the similar energy
    version, WattHours == Volts * AmpHours (giving examples using the
    battery mAh ratings). Your reason for mentioning this is ... ???

    Totally wrong. First, an alkaline "battery" contains more than
    one cell. But that's a nit. An alkaline cell does not always
    produce 1.5 volts. Fresh alkaline batteries can, if they're not
    heavily loaded, causing an internal voltage drop due to internal
    resistance. Second, Energizer's data sheets state that the
    efficiency (and I quoted it) is 87%, which is extremely efficient.

    You evidently have no idea what I was talking about. Where did
    you imagine that anything was said about buffering alkalines? Check
    the data sheets on Energizer's web site to see what their CHAA and
    CH2AA charging devices are all about. They're intended to be used
    in conjunction with Li-Ion powered cell phones, and can either
    charge the cell phone's internal power pack or help power the cell
    phone while it is being recharged. If anything can be considered to
    be buffered, it's the cell phone's battery (often a single cell),
    not the AA cells in the external charger which are buffering or
    charging the cell phone. Ultra capacitors weren't mentioned and as
    far as I can tell aren't used in Energizer's charging devices. Are
    they in any way relevant? FWIW, the Energizer chargers are widely
    available in many pharmacy/convenience stores, electronics/camera
    stores, etc. The CH2AA sells for about $20 and includes a pair of
    lithium AA cells. Join me in another several cups of coffee. You
    appear to need a jolt of some caffeine. :)
     
    ASAAR, Nov 23, 2006
    #33
  14. void

    if Guest


    My camera has a 3.7V 1150mA lithium ion cell. It is exactly the same
    overall size as 3xAAA NiMH cells which give 3.6V & 900mA. So the lithium
    ion gives about 25% more power, but costs 3 times as much. In my view the
    litium ion thing is a rip off, and more camera manufacturers should provide
    contacts for AAA as an alternative. Some cameras (eg. Ricoh GR) do give
    this option so it is certainly viable, and a very useful backup.



    --
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    if, Nov 25, 2006
    #34
  15. void

    if Guest

    Someone mentioned lithium ion being lighter than NiMH. Well I just put the
    above batteries on the kitchen scales, not very accurate at this weight
    range but the lithium are indeed a bit lighter, maybe 30g compared to about
    40g for the NiMH. Not really worth bothering about unless your camera takes
    a much bigger battery pack.


    --
    _______________________________________________________

    When you make your mark in the world, watch out for guys with erasers.
    -- The Wall Street Journal
    _______________________________________________________
     
    if, Nov 25, 2006
    #35
  16. void

    Phil Wheeler Guest

    But Li AA cells are about 60% the wt of alkaline
    AAs .. and last much, much longer.

    Phil
     
    Phil Wheeler, Nov 25, 2006
    #36
  17. Practical application. Lithium Energizer e2 AA's 400 to 500 shots and
    they will not expire until long after my death. Very readily available
    and reasonably priced.
    OEM NiMH rechargable AA Batteries new, maybe ninety shots if your
    lucky.
    Aftermarket NiMH one year old maybe fifty shots if your lucky. Fairly
    avalaible, not exorbitantly priced.
    I do not use Li-Ion batteries in my still camera but I use them in my
    video camera and my laptop, The biggest drawbacks I have found in them
    is they're only good for about one year and then they discharge much to
    rapidly and finding replacements at the corner drug store is not likely
    to happen and they're incredibly expensive.
    Turn off the LCD display and use the little viewfinder if you want to
    maximize the number of shots you can take with a single charge.
    The November 2006 edition of Wired Magazine has a good article on the
    future of batteries.
     
    silverthreads, Nov 26, 2006
    #37
  18. void

    ASAAR Guest

    That's less true than it used to be. Based on Energizer's data
    sheets, their lithium L91 AA cells are rated at 3000 mAh, which they
    indicate varies with load, but according to their Constant Current
    Performance chart (with a single curve based on cutoff at 0.9v), the
    3000 mAh appears to be pretty uniform at loads from 10ma to 1000ma.
    From memory I think that Energizer rates their alkaline E91 AA cells
    at 2850 mAh, but a similar chart on the E91's data sheet shows that
    it supplies about 3000 mAh at a 10ma load, about 2400 at a 100ma
    load and slightly less than 1000 mAh at a 1000ma load. Visual
    interpolation was used since this chart doesn't have a curve for a
    0.9v cutoff, but has three (1.2v, 1.0v and 0.8v). This indicates
    that older cameras that were very power hungry could sometimes get
    200% greater life using lithium AAs vs. alkalines. But the more
    efficient recent cameras might only see a 20% to 50% advantage,
    depending on the camera and how it is used. For very low drain
    applications drawing less than 20ma, such as clocks, smoke alarms
    and a few low power speakerless portable radios, lithium and
    alkaline AA cells have virtually the same capacity. These values
    assume reasonable temperatures of 21ºC. Performance at lower
    temperatures is only shown for currents of 250ma, and at 0ºC,
    lithium AA capacity appears to be reduced by about 2% to 3% but
    alkaline loses considerably more, about 50% of its 21ºC capacity.
     
    ASAAR, Nov 26, 2006
    #38
  19. Are you talking about AA lithium cells? Those are about 1.6 V per cell.
    But they are *not* lithium ion cells, and they are not rechargeable.

    The problem is that there are about 5 different "lithium" chemistries in
    use in consumer products, all with different characteristics, and most
    of them are not rechargeable. So it's easy to confuse "Lithium Ion"
    with any of the other lithium chemistry cells.

    Dave
     
    Dave Martindale, Nov 26, 2006
    #39
  20. They were wrong. I have 2700 mAh cells for my Canon PS A620, and I
    tried to wear the batteries out taking photos and have yet to succeed.


    If you have a good set of NiMH cells and a decent charger, they'll take
    you a long way.

    30 - 40 shots maybe with Alkaline primaries . . .

    At this point in the game, I've replaced my camera's 2700 mAh Sanyo
    cells with the Sanyo Eneloop cells. While their capacity is rated @
    2000 mAh, they're perfect because I don't use my camera every day, and
    it's not uncommon for it to be put away for a week or 2 at a time.
    (Sanyo claims the eneloops will retain 85% of their charge after 1 year
    of non-use at reasonable room temperatures)

    If I'm going to be doing heavy photo shooting (such as going on
    vacation), I'll use the 2700 mAh cells because they pack more power but
    have a higher self-discharge rate.
     
    [email protected], Jan 13, 2007
    #40
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