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  1. #1
    Join Date
    Oct 2004
    Location
    Southern California
    Posts
    25

    Batteries for Z740. CRV3

    I found a place on line that sells reasonably-priced high-powered (1600) rechargeable CRV3 batteries for the Z740. With shipping they come out to about $8.00 each for 2. Their site is http://www.power101.com/home.htm If they don't have the batteries at their website, they also have them listed on eBay. I recommend buying a charger at the same time as the batteries, as the dedicated CRV3 charger seems to be the only way to recharge the rechargeable CRV3 batteries. Plus you save on shipping by buying both at the same time. Also see note below.
    Last edited by tgaf; 05-08-2005 at 09:35 AM.

  2. #2
    Join Date
    Oct 2004
    Location
    Southern California
    Posts
    25

    Unhappy CRV3 follow-up

    The rechargeable CRV3 batteries do not recharge in my Kodak printer/camera dock. A dedicated charger is needed. Also, I have found a RCRV3 battery that is promoted as a replacement for the CRV3. I purchased one of these along with charger and found out that the RCRV3 charger will not recharge regular rechargeable CRV3 batteries. Live and learn.
    Last edited by tgaf; 05-08-2005 at 09:36 AM.

  3. #3
    Resistor Guest
    You have to look at history a bit.

    CRV3 battery originally appeared as TWO AA 1.25V NiMH
    rechargeable cells in series. Thus delivering about
    2.5V - 2.4V voltage while being discharged in the camera.

    Two standard AAs will deliver about 3.1V - 2.5V while being
    discharged, so most cameras will be designed to operate
    100% fine from about 3.5V down to about 2.4V input.

    When Li batteries appeared having a definite advantage of
    1) no memory effect which all Ni-based batteries have
    (inspite of desceiving advertising with no-mem words)
    and 2) virtualy no self discharge - which Ni-MH batteries
    have at almost 5% capacity per day - it was a definitely
    good idea to make Li based CRV3's.

    However, most rchargeable Li-based technology delivers
    4.2V per cell when fully charged. Thus a Li-based CRV3
    battery has a completely different design than a Ni-MH
    CRV3. It has two cells in parallel. But to deliver the
    voltage to the camera it uses a circuit to drop the voltage.
    Depending on the price/quality of the circuit board inside
    the Li-based CVR3 battery - it will either be two diodes
    paralleled in reverse, or a more complex voltage regulator
    chip and a Mosfet transistor.

    In either case, to charge these CRV3's you need a current
    controlled voltage source with auto-shutff just as with any
    other Li-Ion batteries. And that's exactly why Li-Ion CRV3s
    have special chargers. Power101's CRV3 description actually
    states that: http://www.power101.com/item.htm?id=60095
    "NOTE: This battery is designed for Li-Ion CRV3 chargers.
    It will be damaged if you use a charger designed for Ni-MH
    CRV3 batteries."

    The problem here lies in the method with which Ni-MH are
    charged or "reconditioned". The cheap chargers will just
    have the transformer output through diodes and a resistor
    directly to the battery terminals. Thus providing what
    Ni-MH chemistry requires - more or less constant current
    charging. The more expensive reconditioning chargers will
    also apply discharging pulses - necessary to "decrease"
    the memory effect by shaking the crystalllized chemistry.
    The first method will just accumulate "memory effect", i.e.
    crystallisation and the original Ni-MH battery will be at
    about 50% of its capacity within 2 years. The second
    method abuses the battery, but charges it better. The
    net result is the same 2-year 50% life expectancy, however
    the battery can be safely charged just before use.

    Usually, both of these charging methods will still be somewhat
    voltage controlled, and should not damage Li-Ion CRV3. They
    will not charge them either. However, some cheap chargers
    that will not have a voltage control over about 4.4V for charge
    or cut off at about 2.2V for discharge pulse - will seriously
    damage Li-Ion batteries resulting in total capacity loss.

    However, inspite of all these, if you use a camera that requires
    2 AA batteries or a CRV3 battery - because of the 5% per day
    capacity loss in Ni-MH you probably ran through a lot of times
    when you take these batteries charged just 1-2 weeks ago
    and not being able to even take 20 shots with it. So a Li-Ion
    CRV3 with overnight charging and laying freely for months
    without self-discharge is a very valuable alternative.

    These Li-based batteries don't have to be cycled or charged
    just before use and are much more convinient. The charger
    is just a small cost compared to the inconvinience of Ni-MH.

    You can actually read: http://www.power101.com/FAQ.htm
    in particular on "How to extend/prolong Li-Ion battery life"
    and "What is memory effect".

    I have to disclose that I am affiliated with Power101.com.

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