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External AA Battery Pack for the TE

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Anonymous
January 25, 2005 10:48:31 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

After reading here about the construction of an external AA battery pack for the
TE using Radio Shack parts I decided to try one. I got a 4 battery AA pack, and
a few connectors so that I can switch the charge cord between the wall wart and
the battery pack. The cost was around US$3 so not too bad. The circuit was
simple, just feed the 6 volt battery pack output (watch the polarity of course)
into the charging socket. It worked fine.

Being curious I also made an inline adaptor that fed the charging current to a
ma meter so that I could monitor it. I found that even when the internal battery
is discharged as little as 10% the initial charging current is 510 ma. And if
you're down 80% the initial charge current is still 510ma. (So those 500 ma wall
warts are really needed.) As the unit comes up to full charge the charging
current drops down and eventually stops at around 15 ma. This is a great way to
tell when the unit is fully charged and I may just make this meter a permanent
fixture when using the wall wart. Another interesting thing I found is that when
full charge is reached I can easily tell how much current various operations on
the TE take. I just subtract the 15 ma. For example when I turn on the unit the
current jumps to 115 ma, so the screen at the lowest brightness and the
processor idling takes about 100ma. Increasing the screen brightness to the top
stop makes it go up to a whopping 175 ma. Doing various operations (loading
programs ect) makes it momentarily jump around in the 150 ma area (screen back
on low). There was no noticeable difference with the SD card in or out. Later
I'll take some readings playing music, ect and pass it on. For ebook reading it
stays at around the 115 ma level. AA batteries are rated at 2850 mAh. Allowing
for losing some of that capacity because of long constant use, that translates
to around 20 hours on an external pack. That seems too good to be true. We'll
see... ;) 

More about : external battery pack

January 25, 2005 12:56:09 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

On Tue, 25 Jan 2005 07:48:31 GMT, AaronJ wrote:

> For ebook reading it stays at around the 115 ma level. AA batteries are rated
> at 2850 mAh. Allowing for losing some of that capacity because of long constant
> use, that translates to around 20 hours on an external pack. That seems too
> good to be true. We'll see... ;) 

Whatever results you get, I have a feeling that a fresh set of
2300 mah or 2500 mah NiMH AAs will outlast alkaline AAs, which
appear to be what you're using. And as the PDA's load increases,
the NiMH's advantage should also increase.
Anonymous
January 25, 2005 7:16:07 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

BillB <rainbose@earthlink.newt> wrote:

>Whatever results you get, I have a feeling that a fresh set of
>2300 mah or 2500 mah NiMH AAs will outlast alkaline AAs,

Even though my alkalines are rated at a higher capacity of 2850 mAh you may be
right. First, NiMH's have a lower full charge voltage. A set of 4 NiMH's would
be around 5+ volts instead of the alkalines 6+ volts. My TE wall wart is rated
at 5.5 (measures 5.6) volts. I don't yet know how low the input charging voltage
can go before the TE charging circuit no longer accepts current. This may be a
limiting factor on the *useable* capacity of both types of batteries.

>And as the PDA's load increases the NiMH's advantage should also increase.

The AA alkalines seem to handle the max 500 ma charging current just fine so I
don't see any load advantage there. However alkalines have a deeper discharge
rate. If that lowest allowable charging voltage I mentioned above were say 5
volts, the alkalines may dive below that voltage quicker than the NiMH's with
their flatter discharge curve. But I just put the pack together yesterday. As
time goes on I'll learn more. Thanks for your comments...

BTW A new mystery. The above setup which works just fine on my TE refuses to
work on my Zire72. The Z72 flat out refuses to accept any current (not even a
trickle) from the battery pack, just as if it were an open circuit. I know the
pack is ok because all I'm changing is the charging plug from the TE to the Z72.
Yet both PDA's charge just fine from the same wall wart (measures 5.6V) and same
car charger (measure 5.3V). The AA battery pack measures 6.3V. Something is
different in the Z72's charging circuit but what? My first guess is an
overvoltage circuit since the higher voltage of the AA battery pack is the only
difference I see at first blush. Unfortunately I don't have a variable supply to
test this out (yet). Any other ideas?
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Anonymous
January 25, 2005 7:16:08 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

<noemail@noemail.com> wrote:
<...snip...>
> Something is
>different in the Z72's charging circuit but what? My first guess is an
>overvoltage circuit since the higher voltage of the AA battery pack is the only
>difference I see at first blush. Unfortunately I don't have a variable supply to
>test this out (yet). Any other ideas?

For a quick test to verify that theory, you can insert one or more
silicon diodes in series between the battery pack and the PDA.
Each one will lower the voltage applied to the Zire by ~0.7 volts.
Just make sure they are properly rated for the current you are using.
(I.e. they should be power rectifiers, not small signal diodes.)

Roberto Waltman.

[ Please reply to the group,
return address is invalid ]
January 25, 2005 7:54:46 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

On Tue, 25 Jan 2005 16:16:07 GMT, AaronJ wrote:

> The AA battery pack measures 6.3V. Something is
> different in the Z72's charging circuit but what? My first guess is an
> overvoltage circuit since the higher voltage of the AA battery pack is the only
> difference I see at first blush. Unfortunately I don't have a variable supply to
> test this out (yet). Any other ideas?

Don't use fresh AA's. :) 
Anonymous
January 25, 2005 10:54:58 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

Roberto Waltman <usenet@rwaltman.net> wrote:

><noemail@noemail.com> wrote:
><...snip...>
>> Something is
>>different in the Z72's charging circuit but what? My first guess is an
>>overvoltage circuit since the higher voltage of the AA battery pack is the only
>>difference I see at first blush. Unfortunately I don't have a variable supply to
>>test this out (yet). Any other ideas?
>
>For a quick test to verify that theory, you can insert one or more
>silicon diodes in series between the battery pack and the PDA.
>Each one will lower the voltage applied to the Zire by ~0.7 volts.

Yep that did it. Using one diode I dropped the voltage to 5.3V and the Zire72
seemed to take a normal charging current from the battery pack. So overvoltage
was the problem on the Z72 (only). Interestingly I found the Zire 72 would also
charge at 4.5 volts (using 3 batteries - the green led lit and the icon had the
lightning bolt as normal and it was drawing the same current as when on the wall
wart). So that bodes well for using up all of the battery capacity of the
alkalines with their steep discharge voltage curve.

Perhaps at this point I should warn those who might try a 6 volt external
battery pack with their own *TE* that if Palm thought it important enough to add
an overvoltage protection circuit in the later Zire72 model that was missing in
the TE, then there might just be a good reason for it... ;) 

Another BTW:
Some more measured TE currents:
Screen high- 175 ma
middle- 150 ma
low- 100 ma
off- 70ma

In the past I loaded and app that allowed me to turn the backlight off when I
was outside so as to save the battery. This measurement kind of shows the effort
wasn't really worth the trouble. There's not that much difference between the
low stop and off...
Anonymous
January 25, 2005 11:55:07 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

BillB <rainbose@earthlink.newt> wrote:

> Don't use fresh AA's. :) 

You thought you were joking but I think you actually have the best solution.

After using a diode to drop the voltage to get the Zire72 to charge, and messing
around using the battery pack awhile, I now find the Zirre72 will charge
*without* the diode. The voltage is now reading 6.0 volts even, so the
overvoltage protection must kick in at slightly above 6 volts, cause my earlier
6.3 volts just wouldn't work.

So in my final battery pack design do I include a diode, or do I just wire in a
shorting switch for use with new hot batteries? I mean 10 to 15 seconds of a
dead short ought to bring them down enough don't you think? Nah, probably it
would just be easier to buy my batteries at the Dollar Store... ;) 
Anonymous
January 25, 2005 11:58:09 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

In article <t8bdv0tu98p7qnebk1jmdr350j8ncpev1g@4ax.com>, AaronJ
<noemail@noemail.com> wrote:

> BillB <rainbose@earthlink.newt> wrote:
>
> > Don't use fresh AA's. :) 
>
> You thought you were joking but I think you actually have the best solution.
>
> After using a diode to drop the voltage to get the Zire72 to charge, and
messing
> around using the battery pack awhile, I now find the Zirre72 will charge
> *without* the diode. The voltage is now reading 6.0 volts even, so the
> overvoltage protection must kick in at slightly above 6 volts, cause my
earlier
> 6.3 volts just wouldn't work.
>
> So in my final battery pack design do I include a diode, or do I just
wire in a
> shorting switch for use with new hot batteries? I mean 10 to 15 seconds of a
> dead short ought to bring them down enough don't you think? Nah, probably it
> would just be easier to buy my batteries at the Dollar Store... ;) 

This all sounds fun in a geeky way (not that I object to that). But there
are external battery packs available for cheap.
January 26, 2005 1:48:55 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

On Tue, 25 Jan 2005 20:55:07 GMT, AaronJ wrote:

>> Don't use fresh AA's. :) 
>
> You thought you were joking but I think you actually have the best solution.

Playful perhaps, but serious too. I tend to have lots of alkaline
batteries in all kinds of condition, and several decent battery
testers (can test them under different loads).


> So in my final battery pack design do I include a diode, or do I just wire in a
> shorting switch for use with new hot batteries? I mean 10 to 15 seconds of a
> dead short ought to bring them down enough don't you think? Nah, probably it
> would just be easier to buy my batteries at the Dollar Store... ;) 

If they're 'heavy duty' batteries and not alkalines, it wouldn't
be wise to spend even pennies at the dollar store. If they're
alkalines and even if near the expiration date, they may still have
too high a voltage. I'd want to try NiMH AAs though. They're
relatively inexpensive - you should be able to get 4 of them for $10
or less and they'd easily replace hundreds of dollars worth of
alkalines. If 4.8 volts is too low, a fifth would bring you up to 6
volts, but that would introduce charging complications with most
battery chargers. For my final semi-serious solution, use 4 AAA
alkalines. Under load they'd provide a slightly lower voltage than
4 AA cells. The disadvantage is that you'd probably get a bit less
than 1/2 the life of AAs with no reduction in price.
Anonymous
January 26, 2005 8:45:46 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

guy@ether.net (Guy Bannis) wrote:

>This all sounds fun in a geeky way (not that I object to that).

Yes, well at least I haven't busted anything expensive (yet). I think I'm gonna
retire my m125 now. This homebrew battery pack should easily give me a week of
camping. It should also be good for reading on long plane trips if I can get it
by the Feds... ;) 

>But there are external battery packs available

Of course, but that's no fun.

>for cheap.

So far I've got about US$3 invested...
Anonymous
January 26, 2005 9:02:32 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

BillB <rainbose@earthlink.newt> wrote:

> it wouldn't be wise to spend even pennies at the dollar store.

Now that time *I* was the one who was joking...

>If they're alkalines and even if near the expiration date, they may still have
>too high a voltage.

I found this little warning on a commercial battery pack ad today: 8-0

We only recommend use with 1.2 volt Rechargeable Cells (High Capacity NiHM
Rechargeable for maximum performance). Even with Voltage protection, use of
standard 1.5 volt Cells could be generating voltages which are higher than those
produced by your normal charger. Only use 1.5 Volt cells if you are sure it is
not going to damage your model of device or battery.

Maybe I'll just leave that little dropping diode in there...permanently!!

>I'd want to try NiMH AAs though. They're relatively inexpensive -

I just wanted to get away from the hassle of carrying a wall wart on trips, and
especially wanted to stop climbing behind furniture in motel rooms trying to
find a plug... ;) 
Anonymous
January 26, 2005 9:13:01 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

"AaronJ" <noemail@noemail.com> wrote in message
news:o u7ev0ds43uh2t6uo8jvvd55u376fs25pk@4ax.com...
> guy@ether.net (Guy Bannis) wrote:
>
>>This all sounds fun in a geeky way (not that I object to that).
>
> Yes, well at least I haven't busted anything expensive (yet). I think I'm
> gonna
> retire my m125 now. This homebrew battery pack should easily give me a
> week of
> camping. It should also be good for reading on long plane trips if I can
> get it
> by the Feds... ;) 
>
>>But there are external battery packs available
>
> Of course, but that's no fun.
>
>>for cheap.
>
> So far I've got about US$3 invested...

More power to ya.

That's bad, even for me...
January 26, 2005 10:00:53 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

On Wed, 26 Jan 2005 06:02:32 GMT, AaronJ wrote:

>> it wouldn't be wise to spend even pennies at the dollar store.
>
> Now that time *I* was the one who was joking...

I was looking for even a weak excuse to type "pennies at the
dollar store". :) 


> I just wanted to get away from the hassle of carrying a wall wart
> on trips, and especially wanted to stop climbing behind furniture
> in motel rooms trying to find a plug... ;) 

That's better than looking behind furniture in motel rooms trying
to find a bug. :)  For a really small, easy to carry "smart"
charger, look for one that Radio Shack hides in their toy electric
car section. It's 1 1/4" x 1 1/2" x 3 1/4" in its normal collapsed
state (about 1/2 the size of most moderate sized wall warts,
requires no line cord (an AC plug flips out) and expands to accept
from 1 to 4 AA or AAA cells, NiCad or NiMH. It has an Xmods decal
on it and shows Cat. No. 23-350. It's priced somewhat more than
$20, maybe $23 or $24 IIRC, but is packaged with 8 NiMH AAA cells.
RS will sell you the same 8 AAAs without the charger for nearly the
same price. Too bad the package doesn't include 8 AAs instead.
Anonymous
January 26, 2005 11:55:53 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

http://froogle.google.com/froogle?sourceid=navclient&ie...

I've got one for my T3, will recharge to about 70 to 80 % capacity.


On Wed, 26 Jan 2005 05:45:46 GMT, AaronJ <noemail@noemail.com> wrote:

>guy@ether.net (Guy Bannis) wrote:
>
>>This all sounds fun in a geeky way (not that I object to that).
>
>Yes, well at least I haven't busted anything expensive (yet). I think I'm gonna
>retire my m125 now. This homebrew battery pack should easily give me a week of
>camping. It should also be good for reading on long plane trips if I can get it
>by the Feds... ;) 
>
>>But there are external battery packs available
>
>Of course, but that's no fun.
>
>>for cheap.
>
>So far I've got about US$3 invested...
Anonymous
January 26, 2005 9:05:45 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

In article <ou7ev0ds43uh2t6uo8jvvd55u376fs25pk@4ax.com>, AaronJ
<noemail@noemail.com> wrote:

> So far I've got about US$3 invested...

Not counting the value of your time ... :) 
Anonymous
January 27, 2005 2:26:17 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

guy@ether.net (Guy Bannis) wrote:

>In article <ou7ev0ds43uh2t6uo8jvvd55u376fs25pk@4ax.com>, AaronJ
><noemail@noemail.com> wrote:
>
>> So far I've got about US$3 invested...
>
>Not counting the value of your time ... :) 

In retirement time has no value. But fun is priceless... ;) 
Anonymous
January 27, 2005 8:46:13 AM

Archived from groups: comp.sys.palmtops.pilot (More info?)

>guy@ether.net (Guy Bannis) wrote:

After some thought please allow me an alternate response:

>>But there are external battery packs available

Today I wired together a few parts from my junk box: An old cheapie analog ma
meter, the battery box, a few resistors, a switch, a few connectors, and a small
case. This new improved battery box will do the following:

-Supply current to the PDA from either the wall wart, or when disconnected and
portable from the internal alkaline AA batteries.

-Indicate the voltage of the AAs under load which will show their condition.

-Indicate the charge current being drawn by the PDA. This will show the charge
level of the PDA battery, show when charging is done, and be helpful in spotting
a deteriorating PDA battery.

Any commercial AA battery packs on the market that will do this?

> for cheap.

And so far I'm still at the 3 buck level... ;) 
Anonymous
January 27, 2005 10:14:27 PM

Archived from groups: comp.sys.palmtops.pilot (More info?)

In article <4cqgv099f3oorjpnrr49q5lm70i4ekdd5m@4ax.com>, AaronJ
<noemail@noemail.com> wrote:

> >guy@ether.net (Guy Bannis) wrote:
>
> After some thought please allow me an alternate response:
>
> >>But there are external battery packs available
>
> Today I wired together a few parts from my junk box: An old cheapie analog ma
> meter, the battery box, a few resistors, a switch, a few connectors, and
a small
> case. This new improved battery box will do the following:
>
> -Supply current to the PDA from either the wall wart, or when disconnected and
> portable from the internal alkaline AA batteries.
>
> -Indicate the voltage of the AAs under load which will show their condition.
>
> -Indicate the charge current being drawn by the PDA. This will show the charge
> level of the PDA battery, show when charging is done, and be helpful in
spotting
> a deteriorating PDA battery.
>
> Any commercial AA battery packs on the market that will do this?
>
> > for cheap.
>
> And so far I'm still at the 3 buck level... ;) 

My time is worth more ...
!