wow   being kind  to batteries sure did not help my less than 2 year old macbook pro  it needs a new battery  after less than 400 recharge cycles   thanks apple    yet the abused beat up old 10 yea rold laptop sitting in my desk drawr still runs and holds a charge  and the battery is user replacable    something is wrong with this picture don't ya think?   anyway    i get great battery life in excess of 35 hours I think   i hv eonly  recharged my battery a doen times, since I usually operate from the ac power. if I do got o battery I run it down before going back to ac just to be nice... so it will probably die in another year


On Feb 17, 2012, at 9:46 AM, Martin McCormick wrote:

> Thanks for the very useful messages. In addition to the
> electrostatic effects of a nearby lightning strike,  there are
> also electromagnetic inductive effects. The mechanism is
> relatively straight-forward. What is hard to comprehend is the
> magnitude of the energy levels involved which is why really
> bizarre things can and do happen.
> 
> 	Lightning energy involves so many huge numbers that it is
> hard to get our brains around them. Lightning strikes are
> measured in the hundreds of millions of Joules. A Joule is 1
> watt per second which, by definition, makes a watt-hour equal to
> 3.6 million Jules or 3.6 megajoules. A pretty decent lightning
> strike can deliver hundreds of megajoules to Earth in a few
> millionths of a second which generates a strong magnetic field
> in whatever just got hit.
> 
> 	Any time you pass a current through a conductor, you get
> a magnetic field and anytime you take a piece of metal and sweep
> it through a magnetic field, voltage magically appears in the
> conductor. This is how transformers work and also how a
> lightning strike might generate enough magnetism briefly to
> produce currents in the circuit board of a device that is not
> connected to anything.
> 
> 	The magnetic field decreases according to the law of
> inverse squares, but if you have enough energy to power your
> house for a day suddenly unleashed 20 feet away, it isn't going
> to take much to produce enough voltage to ruin an IC on a
> circuit board.
> 
> 	As a bit of trivia, lightning energy increases as you
> get closer to the Earth's Equator. Florida reports the most and
> worst lightning damage each year.
> 
> Martin McCormick WB5agz
> 
> Lloyd Rasmussen writes:
>> You should get your player out of storage and test it.  It should work on 
>> AC
>> power, but it might not run on battery anymore.
>> 
>> While the player is unplugged, its NiMH battery self-discharges; a process
>> that goes faster if the player is stored in a warmer place.  In addition,
>> the gas gauge chip is permanently connected to the battery pack, and it,
>> too, draws a small amount of current, a few microamperes.  These factors 
>> add
>> up.  Early instructions to libraries said that if a player was going to be
>> stored for more than a few months, the battery should be disconnected.  
>> For
>> this nominal 7.5-volt pack, if the total voltage falls below a value like 
>> 3
>> volts (I don't remember the exact number right now), the gas gauge chip 
>> will
>> inhibit charge until the voltage goes higher than that value.  The early
>> players will thus get into a state where they cannot recharge their own
>> battery packs.  You will find similar advice about disconnecting the 
>> battery
>> for modern BrailleNotes and many other devices, for various reasons.  In 
>> the
>> case of the notetakers, they don't fully shut down when you flip the power
>> switch to Off, and run their batteries down that way.
>> 
>> I saw these instructions and knew that library people were unlikely to
>> follow them, and that consumers might not get their players plugged in as
>> soon as they received them.  I realized that if we could put a diode and
>> resistor between the 5-volt regulated bus and the positive terminal of the
>> battery, we could over a period of several minutes bypass the charging
>> circuit and trickle-charge the battery up to a high enough voltage that 
>> the
>> gas gauge chip would signal for a recharge, at any time that AC power was
>> connected.
>> 
>> After several months of testing at NLS and at the factory, this circuit
>> board modification was made.  I don't remember the exact serial numbers,
>> either, but after about 24,000 advanced players and 70 or 80 thousand
>> standard players, the revised circuit board is used in all production.
>> Since this is surface-mount technology, partially assembled by robotic
>> devices, it's not practical to add these components to an existing circuit
>> board.  We advise librarians to pull the battery from the old player, put 
>> it
>> in a newer one which has the trickle-charge modification, allow it to 
>> charge
>> the battery, then put it back in the old player with a setting that tells
>> the processor that a full battery has been inserted.
>> 
>> Very few battery packs have gone bad so far, but this behavior is part of
>> the reason why library technicians may tell you that there have been some
>> battery problems with the NLS player.
>> 
>> If anyone needs a replacement NLS player of either type, it should be easy
>> to get one from your network library.
>> 73,
>> Lloyd Rasmussen, W3IUU, Wheaton, Maryland
>> Home:  http://lras.home.sprynet.com
>> Work:  http://www.loc.gov/nls
>> 
>> 
>>> -----Original Message-----
>>> From: For blind ham radio operators 
>> [mailto:[log in to unmask]]
>>> On Behalf Of John Miller
>>> Sent: Thursday, February 16, 2012 8:41 AM
>>> To: [log in to unmask]
>>> Subject: Re: OT question about NLS digital player
>>> 
>>> I've had my advanced one for since they first came out, whenever that 
>> is,
>>> I
>>> was one of the first to get it in this area and my battery was good 
>> last I
>>> knew, I haven't used it since I moved where I am now opting for the 
>> victor
>>> streme but last I checked it it was working.
>>> ----- Original Message -----
>>> From: "Ron Canazzi" <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Thursday, February 16, 2012 7:27 AM
>>> Subject: Re: OT question about NLS digital player
>>> 
>>> 
>>>> Hi Harvey,
>>>> 
>>>> It might be the lightning, but I doubt it.  I had a standard digital
>>>> player
>>>> for less than 2 years and all of a sudden--after seldom using it in
>>>> battery
>>>> only mode, when I tried using it for an hour or so, I got the low
>>> battery
>>>> indication and the player shut down.  It still worked with the  power
>>>> cord.
>>>> 
>>>> I called the NLS regional library in Albany, NY  and they said they 
>> had
>>>> been
>>>> having "issues with the NLS new digital players and battery life."  
>> The
>>>> battery--according to the built-in manual--is supposed to last about 5
>>>> years.
>>>> 
>>>> I sent the standard player back and requested and received an advanced
>>>> player.  I like its additional features, but whether the battery will
>>> last
>>>> any longer, I can't yet say--since I've only had the machine for a 
>> month
>>>> now.
>>>> 
>>>> 
>>>> 
>> ...
>> 
>>