I realize I'm responding to an old post, but hopefully this will pick up
some responses;

Bev or others-

If I build a 4 "AA" pack and (properly) hook it in through the adapter
provided for my device (I happen to be using an Ipaq 2215, but consider this
more of a conceptual question for any device) and leave it connected while
using the device, is there any way to calculate or estimate (in advance of
going out and building the thing) how much extra battery life is likely? So
for example...

My Ipaq's main battery is a LI 3.7v 900mAh battery
a single NiMH AA is 1.2v, max rating of 2500mAh

does that multiply straight out, e.g. 4x AA = 4x 2500mAh = 10,000mAh @ 5vdc,
meaning that I'd be able to run 10x as long as on just the main battery? Any
estimates on how much power might be lost just having the power being
converted into the device (e.g. I'm not clear on whether the device runs
directly off the external current, or if it uses external power to recharge
the internal battery, where I might lose some energy in the recharging
circuitry and through heat).

My wife uses hers on research trips, but does have trouble with battery life
(her trips are far away from any power source for recharging, and solar
isn't a good option for her either). If I can make a workable external
battery that would be awesome. Right now she has a backup main battery, but
that sometimes isn't enough, and getting additional main batteries is more
expensive than a handful of rechargables and a radioshack adapter.

Thanks for any additional info,
Keith

"Beverly Howard [Ms-MVP/MobileDev]" <BevNoSpamBevHoward.com> wrote in
message news:uClwcTEBGHA.4084@TK2MSFTNGP12.phx.gbl...
> All ppc's use 5vdc to power and recharge their batteries. If you look
> at the AC adapter that came with the Dell you will see that it accepts
> 110vac-240vac and converts that to 5vdc for the ppc.
>
> Take a look at the automotive adapter as well... many don't list it on
> the case, but those that do will show that the input is 12vdc and the
> output to the ppc is 5vdc.
>
> _if_ you can obtain the appropriate connector and know the power pins
> and polarity, you can connect that to a 4 "AA" battery pack (which
> outputs 5vdc) and have a direct path from the "AA"'s to charge and power
> the ppc.
>
> A usb sync/power cable has four conductors. Two of those conductors are
> for data transmit and receive, one is ground and the other is 5vdc.
> With that information and a "usb a" female connector added to a 5vdc
> battery pack, you have power without the need for voltage conversion.
>
> http://www.starmount.co.uk/s_usbpin.htm
> http://support.dell.com/support/edocs/monitors/2005FPW/English/about.htm
>
> Beverly Howard [MS MVP-Mobile Devices]

"KR" <nospam@nospam.com> wrote in message
news:O4A6GrNLGHA.4060@TK2MSFTNGP10.phx.gbl...
>I realize I'm responding to an old post, but hopefully this will pick up
> some responses;
>
> Bev or others-
>
> If I build a 4 "AA" pack and (properly) hook it in through the adapter
> provided for my device (I happen to be using an Ipaq 2215, but consider
> this
> more of a conceptual question for any device) and leave it connected while
> using the device, is there any way to calculate or estimate (in advance of
> going out and building the thing) how much extra battery life is likely?
> So
> for example...

Don't bother building it. Search ebay for "ipaq 2215 battery extender" there
are loads for just a few dollars

I had one for my Mitac 168 and it would give me 2 or 3 times normal battery
life, but my new Axim x51 draws too much current for these cheap extenders
and needs something with more oomph. A google suggests that the ones on
ebay will work ok with your ipaq 2215

--
John Blessing

http://www.LbeHelpdesk.com - Help Desk software priced to suit all
businesses
http://www.room-booking-software.com - Schedule rooms & equipment bookings
for your meeting/class over the web.
http://www.lbetoolbox.com - Remove Duplicates from MS Outlook, find/replace,
send newsletters

"KR" <nospam@nospam.com> wrote in message
news:O4A6GrNLGHA.4060@TK2MSFTNGP10.phx.gbl...
>I realize I'm responding to an old post, but hopefully this will pick up
> some responses;
>
> Bev or others-
>
> If I build a 4 "AA" pack and (properly) hook it in through the adapter
> provided for my device (I happen to be using an Ipaq 2215, but consider
> this
> more of a conceptual question for any device) and leave it connected while
> using the device, is there any way to calculate or estimate (in advance of
> going out and building the thing) how much extra battery life is likely?
> So
> for example...
>
> My Ipaq's main battery is a LI 3.7v 900mAh battery
> a single NiMH AA is 1.2v, max rating of 2500mAh
>
> does that multiply straight out, e.g. 4x AA = 4x 2500mAh = 10,000mAh @
> 5vdc,
> meaning that I'd be able to run 10x as long as on just the main battery?
> Any
> estimates on how much power might be lost just having the power being
> converted into the device (e.g. I'm not clear on whether the device runs
> directly off the external current, or if it uses external power to
> recharge
> the internal battery, where I might lose some energy in the recharging
> circuitry and through heat).
>

No, 4 x 2500 mah = 2500 mah.

The reason is that you will have to hook the bateries in series to get the
voltage needed, and 4 x 1.2 will practically get you the voltage needed to
run (4.8 vs 5v), depending on the device and how forgiving it is.

I have ran USB devices off of 4 AA bateries in the past with no problems,
but again it will depend on the device and how much the voltage drop is at
the moment of use ( remember the fomula use of I,V and R...)

One word of caution though if using straight batteries - some lithium
batteries can be of higher voltage than advertised, and a 1.6v range x 4 in
series is suddenly 6.4 volts, which could damage some devices. It might be
worthwhile to watch the battery type, or even better if a 7805 or similar
was used to limit voltages - but if you stick with the rechargeables as you
state it is not such an issue.

"xTenn" <xTennRemoveThisPart@tds.net> wrote in message
news:uK5V93NLGHA.744@TK2MSFTNGP09.phx.gbl...

> No, 4 x 2500 mah = 2500 mah.
[at 5vdc]


Doh! <slaps forehead>
I wasn't thinking clearly, but that make perfect sense.
:)