Brief Review: New Rayovac 15 minute charger

Discussion in 'Digital Cameras' started by David Chien, Sep 9, 2003.

  1. David Chien

    David Chien Guest

    Just out at Walmart and other stores, the latest Rayovac 2 battery and 4
    battery chargers.

    The 2 battery maximum-at-a-time charger unit is an all-in-one design
    with a flip out AC prong in the back while the 4 charger unit has an
    external, plug-in AC adapter.

    This review covers the 2 battery charger.


    The 2 battery charger comes with 2 2000mAh Ni-Mh batteries. The unit is
    moderately compact and can be held in the palm of your hand, but the
    front bulges out enough so that you can't easily slip it into a slim
    pocket. It will fit fine in a jacket pocket, although the slightly
    heavy weight of the unit & batteries will make it sag a bit.

    Flip out the AC prong in the back and plug it into any socket. It
    accepts universal voltage from 100-220v, so you can use it worldwide.

    Right away, the LED light will turn on and the built-in fan in the front
    of the unit will start. In a few minutes, the fan will speed up to the
    sound of a very quite hair drier, or if you have external HD enclosures
    for 3 1/2" drives, then a fan like that. Not too bad, but you can
    easily hear it several rooms down the hall in your house when it is on.

    The fan helps keep the unit and batteries cool as the 16A max charge
    rating on the back of the unit pushes more than 1/C charge into the
    batteries (1/C was the highest recommended charge current for Ni-Mh
    batteries in general before these 15 minute models arrived for safety
    and optimal charging; usually, 1/C = the rated capacity of the battery
    in one hour.). Naturally, this keeps the batteries hot, and you can
    easily expect temperatures of the cells to reach 50 degrees C or higher
    during the charge cycle. You can hear the fan cycle faster and slower
    as the unit continously pulse charges the batteries.

    In about 15 minutes, the charger stops and the cells are charged. You
    still have to wait a few minutes for the batteries to cool down before
    handling them.

    The unit itself accepts both AA and AAA batteries, but the springs are
    stiff, so you'll have a hard time getting them in and out of the unit
    unless you realize you can easily pry them out with a tool like
    screwdriver, or simply rotate the cells round and round while lifting
    them up and out of the charger. This is one of the downsides of this
    charger, but it's not so bad that it overcomes the benefit of having a
    15 minute Ni-Mh charger.

    The cells themselves work just fine in any portable device including

    Normal Ni-Mh batteries charge in this unit overnight, so you'll either
    have to keep your old fast charger and cells, or replace them with new
    ones if you want fast charging of older cells.

    Walmart for $19.99.

    Basically, as long as you don't mind the noise and the difficult to
    remove cells, it's a fine all-in-one charger that beats all other
    chargers on the planet in speed (15 minutes vs. at least 60-100 minutes
    for other rapid chargers). Because no other charger maker has announced
    or released a 15 minute charger, the two Rayovac chargers are the only
    models available today that you can buy and use.

    Despite the downsides, I find the charger to be a keeper.
    David Chien, Sep 9, 2003
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  2. David,

    one big question that you can, of course, not answer yet is how
    many charge cycles the batteries will survive. Actually, if the
    charger is designed properly and never overcharges the
    batteries, they may live quite long.

    Hans-Georg Michna, Sep 10, 2003
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  3. David Chien

    JK Guest

    How much are extra sets of 4 batteries that charge in 15 minutes?
    How much is the 4 battery charger?
    JK, Sep 11, 2003
  4. David,

    thanks for the interesting details!

    My first thought was that it would be crude to charge at full
    current until pressure rises, then cut the charge off entirely.
    I think it would be better to reduce the current somewhat
    gradually as the cell nears full status. Only this would charge
    the battery to the absolute full status.

    But then (a) I don't know whether this is really so and (b) I
    don't know whether they perhaps do reduce the current gradually.

    Hans-Georg Michna, Sep 14, 2003
  5. From what I read on the web page, you get the 15 minute charge *only*
    with a new special design of cell. From someone else's posting, these
    have an internal mechanical switch that senses gas pressure within the
    cell (which rises as the cell goes into overcharge) to terminate the
    fast charge.

    The charger will also charge normal NiMH cells, but only at the
    slow-charge (probably 14 hour) rate.

    So you gotta buy the Rayovac brand cells to get a 15 minute charge.

    Dave Martindale, Sep 14, 2003
  6. Dave,

    thanks for this information! Yes, I later saw the web ads from
    Rayovac, and they confirm what you wrote.

    Interesting idea. Let's see if all the other manufacturers hop
    on the bandwagon, produce compatible cells, etc. They may be
    forced to.

    I also wonder how the internal cell switch can connect and
    disconnect a current of more than 1 A in a creeping fashion.
    Perhaps it has some mechanical hysteresis and really clicks on
    and off.

    Hans-Georg Michna, Sep 15, 2003
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