Off Topic - life expectancy of a laptop

[BillW50]

In choro typed:

It is always wise to shut down the laptop before either removing or
inserting the battery. Better safe than sorry.

I have been removing and replacing laptop batteries under power for
about 30 years now and I never had a problem. I do believe it is a very
bad idea to bang the computer around with the hard drive running.
Because if you are not careful, you start having bad sectors pop up all
over the place.

Batteries of any type have a set number of rechargings before they
start holding less and less juice. And if the battery is left in all
the time, you are obviously going to recharge the battery
unnecessarily and even if the battery doesn't die down, it will
gradually hold less and less juice. If you charge a battery once
every month, 500 maximum charges before the battery starts dieing
down, will go 500/12 years, at least theoretically. You can't
possibly have a battery last that long if you keep the battery in all
the time.
'Nuff said, me tinks!

So unless you actually need to have your laptop running on battery
power, keep the battery out but do not forget to charge it at least
once every few months because it can die down also if it runs out of
juice completely. Make a habit of charging the battery once say at the
beginning of every month or every even numbered month.

I used to say the very same thing. Although some things came up that
made me think otherwise. As I used to have UPS everywhere and just
remove on of my laptop batteries. Thus I baby my laptop batteries and I
can get about 12 years out of them treating them this way. Sounds great
and all. But.

I have lots and lots of laptops. And I have lots and lots of batteries.
And most of my machines are the same model. Like 19 of them only use
three different types of batteries. And I only usually have only one
running at a time. Although sometimes I am running two at the same time.

And even if I keep two batteries in all of the time and throw them away
every 2 years or how ever long they are going to last. I couldn't
possibly wear all of them out in 12 years time anyway. So why keep
protecting them?

Now back to the UPS. Yes they sound great and all. But for running
laptops, not so hot. As you still have to replace UPS batteries. Plus
you have to buy the UPS themselves. So you really are not really saving
money and UPS are far from being portable. So I quit using UPS and went
back to laptop batteries and I like this far better.

 

[Paul]

Per choro:

I cannot cite, but it seems to me like somewhere I read that
applies to NiCad, but not Li.

Maybe somebody who knows can chime in.

NiCad batteries actually have specs. And they'll tell you
what the safe discharge level is for "conditioning". It's
in the 1.0V region (because I have a charger with conditioning
and it drops the battery voltage to that region, per each
cell inserted). Each data sheet is slightly different, and
some might say 0.9V for this value.

When NiCd are placed in series, and discharged as a set, it
can reverse bias the one that holds the least amp-hours,
damaging it. When you think you're running it "down to zero",
some of the cells end up with a temporary negative voltage
across their terminals, caused by a stronger cell in the
battery pack. So generally, shorting NiCD multi-cell packs
from the outside is bad. Shorting each cell individually,
while the pack isn't loaded is better. And draining them to 1.0V
(which is the knee, and very close to zero percent amp-hours),
is best, on a per-cell basis.

The higher capacity (5A-h or 8A-h D-Cells), actually have a
max recommended load current, so when I say "short", I don't
mean just "throw a crowbar across it". Use a load of a known
value, like say something that draws 1 ampere. On the larger cells,
you may get fewer charge-discharge cycles, by running them outside
the spec sheet values (and to some extent, it could actually
be the inferior quality of the battery design in the first place).
With the high capacity cells, the data sheet may be telling you
to spend 5 hours doing the conditioning step.

Lithium "complete discharge", as in "let's leave this
laptop on until it shuts down", turns off the battery
load before it goes below the knee. So the intention,
of the controller in the laptop, is not to discharge
the battery to zero volts. Mainly because, if
left that way, and with the self-discharge property of
the pack, it might end up with a terminal voltage lower
than the "safe to charge" value. So you can't drain them
to zero, like you could with NiCd. And even with NiCd,
there are "good, better, best" ways to do it. If you
actually manage to drain the lithium to zero terminal
volts, the charger in the laptop should refuse to charge it.

When you damage NiCd, they get "whiskers" inside. And people
use a strong current source to "blow out" the whiskers. Of course,
by doing so, the remaining lifetime of the cell will be compromised,
but at least the cell is still being used. The cell will then be
mis-matched to its mates, and it'll be the first cell to drain
below the NiCd knee, while the others still have volts on them.
So it's also the cell that's going to get damaged again. And
this is where a properly designed monitor in the device would
pay off, but is seldom present. My battery powered screwdriver
falls in the category. Crappy charger, and no protection
against reverse bias while discharging. The battery gets
bludgeoned on both charge and discharge steps.

Paul

 

[BillW50]

In choro typed:

The memory effect is supposed to apply to NiCads as you point out but
I *do* believe that it also applies to NiMH and other batteries
including Li-Ion batteries though to a far lesser extent.

I have been recharging batteries for over 40 years. And I have over 40
years experience with Ni-Cad batteries. And I have special lab equipment
that can cycle virtually any battery of virtually any type. It also
records many things like true capacity, capacity for every cycle, time
to charge, etc. And I can dial in the loads, the speed of the charging,
etc.

And even Ni-Cads, which are suppose to have a bad memory effect problem,
I never saw yet. Even using the lab equipment, all recycling does is to
reduce the capacity a tad more than before. If any battery type truly
has a memory effect problem, all of this recycling should improve the
battery capacity at some point. But I have never seen it.

What I have seen from Ni-Cads though is if you leave them alone for
months to years and just let them sit. Then one day grab them and
recharge them and then use them. Now the capacity will be much lower
this first time. Although the next recycling will bring them back to
normal capacity once again.

A common use for Ni-Cads today in laptops is the CMOS/RTC battery, which
is commonly a Ni-Cad. And if the memory effect was a real problem, this
is the worst place to use a Ni-Cad battery. As it isn't easy to recycle
this battery without disassembling the laptop and doing so manually. And
yet, Ni-Cads work well for this application, do they not?

The story I heard once that I have never could verify was that the story
about Ni-Cad memory effect thing was created as a smear campaign to kill
off the Ni-Cad market. Thus the Ni-MH manufactures could make sales. I
don't know if that is true or not. But I can scientifically state there
isn't much to this memory effect thing.

Another point, when you get a new appliance it is always advisable to
charge up the battery fully and I mean fully. Leave it on trickle
charge for far longer. And do run the battery until there is hardly
any charge left in it and repeat this process for at least 4 cycles.
You give the battery its best chance by doing this. Never wise to
start using the whatever it is as soon as you get it out of the box.
Always charge up fully for much longer than is necessary to fully
charge the battery and then use your equipment until the battery is
exhausted. Repeat this process at least 4 times.

I too used to recycles at least 3 times. But the data shows it really
doesn't help no matter how many times you have done it.

I have had 2500 mAh LR6/AA batteries that don't last half as long as
my trusted years old 1700 mAh Kodaks. And this I have established for
myself very, very systematically using them in the same camera,
charging them in the same charger etc etc.

But of course, others can chime in. I am always open to new ideas.--
choro
*****

I never heard of any AA Ni-Cads having either 1700 mAh or even 2500 mAh
capacities. As Ni-Cad capacities are much lower than this. As both of
those sounds like Ni-MH batteries which do come in those capacities.

And yes, most definitely about the difference in quality among battery
manufactures. And the batteries that seem like a bargain are generally
no bargain in the long run. ;-)

 

[BillW50]

In (PeteCresswell) typed:

I guess one question is whether the laptop is pulling power from
the battery or direct from the power supply when it is running
plugged in. Batteries being consumables and all that...

Most laptops use no battery power if the AC power is connected. There
are some laptop designs though that cheats a little bit. And they supply
a bit smaller power supply then they should have designed for it. And
when the laptop is using enormous amount of power for say maxed out CPU
demands, etc, the laptop will borrow some power from the battery to make
up the lack of demand from the AC supply. If you ran these laptops
without a battery, they still would work. Although the CPU and things
would usually run unclocked so it would keep the power demand lower.

 

[BillW50]

In (PeteCresswell) typed:

Per choro:

I cannot cite, but it seems to me like somewhere I read that
applies to NiCad, but not Li.

Maybe somebody who knows can chime in.

Yes, although the BIOS used in these 11 Gateway laptops I have right
here has a battery recalibration mode. How it works is that it
discharges the battery down and then recharges and repeats two more
times. It isn't really doing the recycling thing per se, but the BIOS is
learning the true capacity of the battery instead of trying to remove
any memory effect.

 

[Paul]

A common use for Ni-Cads today in laptops is the CMOS/RTC battery, which
is commonly a Ni-Cad.

Absolutely not.

If you look back 10-15 years ago, maybe.

NiCd leak all over the place, and if not attended to immediately,
can ruin the motherboard area where they sit. That's one reason
they've disappeared for functions like that. They were used in
pin ball machines, to run the NMOS memory chip, and made a mess
in there too.

Modern equipment uses CR2032 family (maybe a CR2016). In a laptop,
instead of a socket to hold them, they use shrink wrap tubing to insulate
the battery.

http://en.wikipedia.org/wiki/CR2032

You must have seen one of these for sale ? I've never heard
of these leaking. The only slight danger, is like a number of
other cell types, you can't charge these, and the maximum
charge current you're allowed without trouble, is 1 microamp.
And it's that high, so that Schottky diodes can be used
to prevent charging. 1 microamp is basically a leakage allocation
for the Schottky diode used to prevent charging. Current steering
diodes are used, so current can only flows out of the coin cell.

http://ts3.mm.bing.net/images/thumbnail.aspx?q=4611425445217598&id=147f8e3bda4847351578d9673b4b42f4

Nickel Cadmium is no longer a preferred technology.
(Even though I like them, nobody else does.)
Some battery companies have given up on them entirely.
The Chinese, have not.

I never heard of any AA Ni-Cads having either 1700 mAh or even 2500 mAh
capacities. As Ni-Cad capacities are much lower than this. As both of
those sounds like Ni-MH batteries which do come in those capacities.

And yes, most definitely about the difference in quality among battery
manufactures. And the batteries that seem like a bargain are generally
no bargain in the long run. ;-)

At least on D sized NiCd cells, there can be an inner cell which is smaller
than the metal outer casing. I don't think they do that with the smaller
ones. So for the smaller ones, it's whatever the charge density will allow.

There is a table here of watt-hours per liter of space, and
NiMH is 300 while NiCd is 140. So close to a factor of 2
difference is to be expected when comparing them. But when you
need electricity at a lower temperature, then the picture changes
a bit. Sometimes an inferior technology, is your friend. Like
still being able to start your car, at a ski resort, after
skiing all day. Not all the battery types are suited to that.

http://www.allaboutbatteries.com/Battery-Energy.html

Paul

 

[J. P. Gilliver (John)]

In choro typed:

I have been recharging batteries for over 40 years. And I have over 40
years experience with Ni-Cad batteries. And I have special lab equipment
that can cycle virtually any battery of virtually any type. It also

Including zinc-carbon and "alkaline"?

records many things like true capacity, capacity for every cycle, time
to charge, etc. And I can dial in the loads, the speed of the charging,
etc.

And even Ni-Cads, which are suppose to have a bad memory effect problem, []
A common use for Ni-Cads today in laptops is the CMOS/RTC battery, which
is commonly a Ni-Cad. And if the memory effect was a real problem, this
is the worst place to use a Ni-Cad battery. As it isn't easy to recycle
this battery without disassembling the laptop and doing so manually. And
yet, Ni-Cads work well for this application, do they not?

As someone else said, not for many years. Tend to be primary lithium: in
desktop machines usually the CR2032, I suspect a different type number
in laptops.

The story I heard once that I have never could verify was that the story
about Ni-Cad memory effect thing was created as a smear campaign to kill
off the Ni-Cad market. Thus the Ni-MH manufactures could make sales. I
don't know if that is true or not. But I can scientifically state there
isn't much to this memory effect thing.

I don't think so, as I remember it being around well before NiMH were
available at all.
[]

I never heard of any AA Ni-Cads having either 1700 mAh or even 2500 mAh
capacities. As Ni-Cad capacities are much lower than this. As both of
those sounds like Ni-MH batteries which do come in those capacities.

Indeed; I don't think I ever came across more than 750, or possibly 800,
mAh in NiCd AA.

And yes, most definitely about the difference in quality among battery
manufactures. And the batteries that seem like a bargain are generally
no bargain in the long run. ;-)

I've found most NiMH (and many other types) _do_ self-discharge; I
haven't really played yet with the ones (certain trade names) that claim
to still hold 75% (or more) after a year. Any thoughts?

 

[charlie]

Summarizing -

Battery on laptops:

The older laptops use a different type of battery than is available
now.

Memory in the battery was much more prevalent resulting the inability
to actually perform a full charge.

My understanding is this has been mostly corrected in the newer
batteries.

However, I still make it a point to completely discharge my laptop
battery once or more times a month. I just unplug when I go to bed,
and recharge when I am ready to work in the morning.

External monitor:

I mostly use my external monitor when I am playing music or watching a
streaming movie online. Extending the screen is a real plus because I
can continue working while being entertained, or duplicate if I need a
large screen to work from.

Back-ups and protecting data:

External hard drives have gotten so cheap, it's worth the money to buy
one or two, and perform a serious disk image backup of entire drives
every couple weeks or so (at least once a month for me), or more often
if I am working on mission critical projects. Losing a couple hours of
work is not as much a concern as losing a weeks worth.

Glasses:

I prefer to dedicated sets as I mentioned before. One for general
reading, and another for computer or more distant visual acuity .

This thread has really digressed from the original questions, but I
hope I haven't missed anything.

TTYL.

MJR

The Li batteries, as a general rule, do not like to be fully discharged.
Once or (better) twice a month seems to be adequate to charge most
laptop batteries.

It's not uncommon to see a 20% drop in capacity after several charge
discharge cycles on many current laptop batteries.

What really irks me is the inclusion of battery monitoring circuity that
makes it difficult to impossible to recover some laptop batteries.
(replacing bad cells, using recovery charging equipment, etc.)

The circuitry has to be reset, and there may or may not be a way to do it.

 

[choro]

In choro typed:

I have been recharging batteries for over 40 years. And I have over 40
years experience with Ni-Cad batteries. And I have special lab equipment
that can cycle virtually any battery of virtually any type. It also

Including zinc-carbon and "alkaline"?

records many things like true capacity, capacity for every cycle, time
to charge, etc. And I can dial in the loads, the speed of the charging,
etc.

And even Ni-Cads, which are suppose to have a bad memory effect problem, []
A common use for Ni-Cads today in laptops is the CMOS/RTC battery, which
is commonly a Ni-Cad. And if the memory effect was a real problem, this
is the worst place to use a Ni-Cad battery. As it isn't easy to recycle
this battery without disassembling the laptop and doing so manually. And
yet, Ni-Cads work well for this application, do they not?

As someone else said, not for many years. Tend to be primary lithium: in
desktop machines usually the CR2032, I suspect a different type number
in laptops.

The story I heard once that I have never could verify was that the story
about Ni-Cad memory effect thing was created as a smear campaign to kill
off the Ni-Cad market. Thus the Ni-MH manufactures could make sales. I
don't know if that is true or not. But I can scientifically state there
isn't much to this memory effect thing.

I don't think so, as I remember it being around well before NiMH were
available at all.
[]

I never heard of any AA Ni-Cads having either 1700 mAh or even 2500 mAh
capacities. As Ni-Cad capacities are much lower than this. As both of
those sounds like Ni-MH batteries which do come in those capacities.

Indeed; I don't think I ever came across more than 750, or possibly 800,
mAh in NiCd AA.

And yes, most definitely about the difference in quality among battery
manufactures. And the batteries that seem like a bargain are generally
no bargain in the long run. ;-)

I've found most NiMH (and many other types) _do_ self-discharge; I
haven't really played yet with the ones (certain trade names) that claim
to still hold 75% (or more) after a year. Any thoughts?

Yes, yes. I've recently bought some Durex Rechargable Active Charge
batteries and they certainly hold the charge and do not seem to
self-drain. However, I cannot vouch for the claim of holding charge 75%
or 80% over a one-year period but they certainly DO hold the charge
well. Far better than standard NiMH rechargeables.

Anyway, it was interesting for me to read both your and Paul's
responses. And thanks for the URLs.--
choro
*****
PS. Why I always think of this brand as Durex beats me!

 

[choro]

I cannot cite, but it seems to me like somewhere I read that
applies to NiCad, but not Li.

Maybe somebody who knows can chime in.

Lithium Ion batteries do not suffer from the "memory effect" issue that
plagued NiCad batteries, so do not benefit from complete discharge /
recharge cycles.

As I understand it, the deeper the discharge before being fully
recharged, the fewer recharge cycles you can expect before the battery
drops to below 75% capacity.

Of course, it generally isn't very practical to just discharge 10% then
recharge, but if you could that would give you the most recharge cycles
(but not necessarily the most total battery life). Discharging to 50%
or 25% before recharging is probably the best compromise, especially
since the batteries age and typically don't last beyond 2 to 3 years no
matter how gently you treat them.

Also, avoid overheating the battery if at all possible, as that
significantly reduces their lifespan as well. Rapid discharge and
rapid charging both generate a lot of heat, so it is probably best not
to run the device at full tilt while on the battery. Of course you
don't have much choice in how quickly most devices recharge their
batteries, but keep them cool while they do so if you can.[/QUOTE]

Me tinks you are right about batteries heating shortening the lifespan
of the battery. Hence I prefer NOT to use fast chargers. Trickle charge
whenever I am not pressed for time.

And certainly batteries should be charged well before they are
completely and utterly drained. However all or most equipment gives up
once the battery is down to a certain percentage of the full charge.
Then is the good time to recharge the battery.

Hence, would you say it would be good practise to have 2 batteries and
swap batteries when the equipment gives up and only THEN recharged the
mostly drained battery? To my mind this seems to be the best practise as
far as batteries go.

 

[choro]

In (PeteCresswell) typed:

Yes, although the BIOS used in these 11 Gateway laptops I have right
here has a battery recalibration mode. How it works is that it
discharges the battery down and then recharges and repeats two more
times. It isn't really doing the recycling thing per se, but the BIOS is
learning the true capacity of the battery instead of trying to remove
any memory effect.

This subject is obviously a lot more complex than I first thought. But
thanks to all who have responded. I try to stick to well known brands
but was disappointed by Synergizer ;-) NiMH Rechartgeables which I
definitely won't be buying again. I wonder who makes the Kodak batteries
which have certainly given ME wonderful service?--
choro
*****

 

[choro]

In choro typed:

I have been removing and replacing laptop batteries under power for
about 30 years now and I never had a problem. I do believe it is a very
bad idea to bang the computer around with the hard drive running.
Because if you are not careful, you start having bad sectors pop up all
over the place.

Better safe than sorry, as they say. It is an extra precaution and good
practise to shut down the computer before moving it anyway. But I do
believe that just inserting or removing battery on a laptop might have
no drawbacks other than the fact that you are moving the laptop while
the HD is active. This alone is good enough for me to shut the damn
thing down before either inserting or removing the battery.

I used to say the very same thing. Although some things came up that
made me think otherwise. As I used to have UPS everywhere and just
remove on of my laptop batteries. Thus I baby my laptop batteries and I
can get about 12 years out of them treating them this way. Sounds great
and all. But.

I have lots and lots of laptops. And I have lots and lots of batteries.
And most of my machines are the same model. Like 19 of them only use
three different types of batteries. And I only usually have only one
running at a time. Although sometimes I am running two at the same time.

And even if I keep two batteries in all of the time and throw them away
every 2 years or how ever long they are going to last. I couldn't
possibly wear all of them out in 12 years time anyway. So why keep
protecting them?

Now back to the UPS. Yes they sound great and all. But for running
laptops, not so hot. As you still have to replace UPS batteries. Plus
you have to buy the UPS themselves. So you really are not really saving
money and UPS are far from being portable. So I quit using UPS and went
back to laptop batteries and I like this far better.

You are certainly right in thinking along these lines but where I live
we have no problems with power outages. Maybe once every 5 to 10 years
and then it is usually back on before you can wink your eye. I remember
once a couple of years ago, the lights blinked but for some reason my
desktop didn't blink. As far as I remmeber, it went on as though nothing
had happened. I wonder whether being powered via a Belkin SurgeMaster
had anything to do with this. I love my Belkin SurgeMaster which not
only provides protection but being the plinth type also raises my
monitor by around 4 cm while providing 4 or 5 (depending on the exact
model) of individually switched outlets + a straight through outlet
which remains on even when the Master On/Off switch is switched off.

I have several of these Belkin Surge Masters that I use around the house
and if this sounds like singing the praises of Belkin Surge Master, I
don't mind in the least. One did go wrong some years back and they
replaced it, no questions asked, under their lifetime guarantee.

Now, *that's* what I call a good Manufacturer's Guarantee (or Warranty
depending on where you live!)

 

[Paul]

You are certainly right in thinking along these lines but where I live
we have no problems with power outages. Maybe once every 5 to 10 years
and then it is usually back on before you can wink your eye. I remember
once a couple of years ago, the lights blinked but for some reason my
desktop didn't blink. As far as I remmeber, it went on as though nothing
had happened. I wonder whether being powered via a Belkin SurgeMaster
had anything to do with this. I love my Belkin SurgeMaster which not
only provides protection but being the plinth type also raises my
monitor by around 4 cm while providing 4 or 5 (depending on the exact
model) of individually switched outlets + a straight through outlet
which remains on even when the Master On/Off switch is switched off.

I have several of these Belkin Surge Masters that I use around the house
and if this sounds like singing the praises of Belkin Surge Master, I
don't mind in the least. One did go wrong some years back and they
replaced it, no questions asked, under their lifetime guarantee.

Now, *that's* what I call a good Manufacturer's Guarantee (or Warranty
depending on where you live!)

The ATX power supply, has a couple big electrolytic capacitors
inside it. The AC line is rectified to high voltage DC, and
the capacitors hold that energy.

(C5 and C6 store DC on the primary...)
http://www.pavouk.org/hw/en_atxps.html

The capacitors also take time to drain. If the computer is
sleeping (+5VSB still running, no fans), the ATX supply can
run for close to 30 seconds, using the juice in the capacitors.
So about the longest holdup time, happens if the computer is
sleeping (suspended to RAM).

If the ATX supply is running at full load (500W on a 500W supply),
the capacitors only have enough juice for 16 milliseconds or so.
So at full load, the "holdup" time is minimal. As the loading
of the PC goes down (like, say, 60W while the desktop is idle),
the holdup time is increased. And that is what prevents a power
company transfer switch, from crashing the computer. Holdup time.

Another limiting factor, is line voltage. Say you're in a
brownout, the AC line is at 90VAC, then, there happens to be a
short outage. Your ATX supply caps last for less time in that
situation. So the holdup time does have a slight dependency
as well, on whether the AC voltage is at a proper level or not
before the event.

If that holdup time feature did not exist, then the usage
of really cheap UPS boxes would not be possible. (Without the
holdup property, the computer would crash or reboot in that case.)
The amount of holdup time on the ATX supply, is sufficient for
compatibility with any UPS. Cheap UPS boxes, when they switch
to battery, have a short "outage" where there is no power.

XXXXXXX________________________ <--- Input from the wall

XXXXXXX___________xxxxxxxxxxxxx <--- Cheap UPS. ATX holdup
On AC No juice UPS on battery supports "flat spot"...

XXXXXXXxxxxxxxxxxxxxxxxxxxxxxxx <--- Double conversion UPS.
On AC UPS on battery No ATX holdup needed.

So the ATX supply is good enough to work with either kind of UPS.

Paul

 

[Zaphod Beeblebrox]

Me tinks you are right about batteries heating shortening the lifespan
of the battery. Hence I prefer NOT to use fast chargers. Trickle charge
whenever I am not pressed for time.

Absolutely, assuming you have the option. Unfortunately, I don't know
of any built-in laptop battery chargers that have that option. In
fact, many built-in laptop battery chargers not only fast charge all
the way to 100%, they continue to flog the battery after it is fully
charged, leading to premature failure of the battery.

And certainly batteries should be charged well before they are
completely and utterly drained. However all or most equipment gives up
once the battery is down to a certain percentage of the full charge.
Then is the good time to recharge the battery.

Hence, would you say it would be good practise to have 2 batteries and
swap batteries when the equipment gives up and only THEN recharged the
mostly drained battery? To my mind this seems to be the best practise as
far as batteries go.

That's not a bad approach, but I prefer to charge when at 25 - 30% or
so rather than letting it get down to where the device turns off. As I
understand it, that extends the life of the battery noticeably.

Having the spare battery does allow you to let the recently discharged
battery cool before recharging, and let the charged battery cool before
using it, which should help with battery life.

 

[charlie]

This subject is obviously a lot more complex than I first thought. But
thanks to all who have responded. I try to stick to well known brands
but was disappointed by Synergizer ;-) NiMH Rechartgeables which I
definitely won't be buying again. I wonder who makes the Kodak batteries
which have certainly given ME wonderful service?--
choro
*****

Completely discharging a Li battery (Particularly LiPos) freely
translates into buy a new battery. As to AA size capacity - - The older
NiCads had lower capacity, lower discharge rates, and generally longer
life. As the battery capacity goes up with the AA NMIH batteries, the
useful life seems to decrease. I have some old Sanyo NiCad AA's that are
several years old, and still hold a charge. Retail NMIH batteries only
seem to last a couple of years at most.

 

[Roy Smith]

No, not at all.

The only "trouble" I had with my latest pair (about 10 years now) was the
manufacturer ground the right eye's varifocal part *backwards*. I could
see really good far away. Naturally, they fixed their screwup
immediately.

My wife does not like them.

I use progressive glasses also, but I use a separate pair for the
computer. The reason is that in order for me to be able to read the
screen I have to use the bottom edge of the lens, so I have to tilt my
head back which gets uncomfortable after a while.


--

Roy Smith
Windows 7 Home Premium 64-Bit
Thunderbird 14.0
Monday, August 06, 2012 8:41:11 AM