Useful links:
Battery meter: http://nitapps.com/, scroll down to see battery_status, http://www.internettablettalk.com/fo...?t=7590&page=2, thread #13
battery extender, ..http://www.internettablettalk.com/fo...ad.php?t=14139
..Tekkeon M1550 using AA batteries
..Iogear mobile, GMP1001W6, a large battery
..Nokia CA-100 cable with step up converter, http://www.internettablettalk.com/fo...ad.php?t=14139, thread #178, or a cheap one from Dealextreme,

http://www.internettablettalk.com/fo...ad.php?t=19879, and one member posted "melt down", thread #157

I would call the test conditions as extreme conditions. Like running MTV for 4 hrs straight with video and audio continuously, even the tablet gets warm! So, I believe in actual ave use, your hrs should be longer.
================================================== ==========
The results are measured on very reproducible environment, 5/01/08 - 5/15/08, 9p till 6a in airconditioned rooms. All batteries are genuine Nokia battery. All experiments start immediately after charge. Most readings are ave of 2 trials in hrs
__________________________________________________ __________________
Time to charge, tablet shut down by self, battery is NOT dead; this may cause harm to your battery according to some review.
Time to stop, tablet shut down by self
Time to start, "battery is full, pls remove source to conserve energy"
With wifi, running kiss TV channel continuously with kmplayer using osso media player, http://www.internettablettalk.com/fo...ad.php?t=19765.
Without wifi, running CBS evening news, Katie Couric May 1, 2008 using media player>player mode>repeat; dl a copy using videocenter, http://www.internettablettalk.com/fo...ad.php?t=18769

If it is not mentioned, that means it is OFF, e.g. V+BT means only video and BlueTooth is on, all else are OFF, ie. audio/wifi are off.
__________________________________________________ _________
.......................N810..................N800. ...............770
Nokia menu........4.0......................3.5.......... .......3.0
To charge..........2.2......................2.2...... ............>8
V.....................5.8......................4.3 .................6.5
V+BT................5.6
V+w.................3.7
V+w+A..............3.4......................2.5
VV+w+A............3.1
VVV+w+A..........3.0
V+w...................-.......................4.1
V+2B..................-.......................6.1
V+4B..................-.......................7.3
mm+V+iGPS........8.1
mm+V+BT GPS.....-.......................7.5

Legion:
V.......... 1square of brightness
VV........ 2 sq of brightness
VVV...... 3 sq of brightness
A.......... 1 sq of audio
w............wifi
B............used alkaline batttery, not fresh
2700, 2000, 1800 are rechargeble NiMH of mAh capacity
mm.........maemo mapper 2.4.1-os2008, at level 5, stand still, in a building
BT GPS....blue tooth GPS
iGPS........internal GPS
__________________________________________________ _________

This is a very busy table. Conclusions:

1) According to the Nokia menu, 770/N800/N810 battery lasts 3.0/3.5/4.0. In actual use, it is aproximately 7.0/4.5/5.5, i.e., 770 has the longest battery life!
2) the charging time is extremely reproducible, it is 2.2 hrs for N8x0 and over 8 hrs for 770 (missing from Nokia menu!)
3) BT left on or MMC boot do not use a lot of energy, whereas wifi is a BIG battery killer. I guess BT headphone with continuous may be a different story.
4) Contrary to common sense, GPS is NOT such a battery killer when comparing to wifi
5) Only audio, no video/wifi, has been reported to last 11 hrs. I have not test that.
6) N810 is slightly better in battery life than N800 in similar conditions (Mara's analysis)

Part II will include battery extenders and ebay/HK knock off batteries

Comments? Suggestions?

If you have done measurements of your battery under ANY conditions, please jump in! And please include conditions audio/video/Wifi/BT etc. The goal is to optimize the best parameters for battery use, say in camping where plug in is NOT that easy.

Oh, please do take a good look at the table. I may not have extracted ALL the conclusions from the data. Feel free to post your observations. The results are for eveybody to use.

Edit: 1/31/09:http://www.internettablettalk.com/fo...hlight=battery,
http://www.internettablettalk.com/fo...372#post261372, thread #6. I will start adding NEW info here on and off.


N810 2.2007.50-2, internal flash boot
N800 2.2007.51-3, internal flash boot
770 4.2007.26-8, MMC boot

bun

Nice work, Bun. Looking forward to part two

Your results confirm that N810 is slightly better in battery life than N800 in similar conditions.

Good point, Mara. When you point it out, I then read across the board, you are right. As I said, I got some raw data, it is up to everybody to extract the results. Thanks,

bun

I get the following for an N810 with OS2008:

Idle, offline mode - 270 hours
Idle, WiFi on, power saving mode - 100 hours
GPS chip on - 11 hours
Idle, WiFi on, power saving mode OFF - 7 hours
Idle, display backlight on - 9 hours
100% CPU (loop doing sqrt), display backlight off - 6 hours

These figures are based on extrapolating from
a graph of "battery-status" output, rather than actually letting the
battery run completely down.

The default WiFi config (under advanced/other) uses a power saving mode. This uses less power than the GPS.
The GPS driver turns the chip off if nothing is accessing it; I used a program that polls it regularly to keep it running, which will run up the CPU, too. It should be possible to save power by reducing the poll interval to the minimum, or by only turning the GPS on every couple of minutes.

http://andrew.daviel.org/N810-FAQ.html#battlast

Re. camping, Nokia make a 12 charger which should charge the battery in 2hrs from a car/boat/motorcycle/snowmobile. I didn't measure, but it should draw about 0.6A as the charger gives 0.89A
at 6V, same as the 110V one.
For wilderness camping, I'd think it ought to be possible to charge from a solar panel or hand crank. But I don't know enough about Li-ion cells to know if charging at, say, 200mA for 10 hours would be acceptable.

This is a very good idea of measuring the relative battery life without actually draining the battery. Excellent idea. Mind to share which portion of the "battery-status" you are using to do the extrapolating and what is the interval and total duration of measurement? Obviously, you are able to extract from "battery-status" to perform the extrapolating, you do it manually or by programming? Mind to share?

The extrapolating may/mayNOT be applicable in obtaining the absolute number, but the relative comparison among different configurations, wifi on/off, gps on/off etc should be valid. This could serve as a good theoretical prediction and would expect to support the data I measured, I hope. GPS data does not agree, ummm........, one of us is wrong. There is ALWAYS argument between the theoretical physicist and the experimental physicist. Something never change :0



Excellent idea.

Edit: I just turned the GPS on, apparantly you are programming to "use" the GPS constantly during the measurement. That may explain the difference in the results. I think my GPS measurement should be considered 'average' use and yours is like extreme situations. Hey, we all can agree





bun

Ah, I just had a flashback to working in the (now deceased) Alliance factory...

It's important to remember that voltage doesn't vary linearly with capacity, so the most useful voltage-based partial-discharge data (for comparison) is the time from a specific starting voltage to a specific ending voltage.

(It's not at all clear, though, whether those voltages should be absolute voltages, or relative to charger shutoff; the charger shutoff point may be constant voltage anyhow, rendering them equivalent, but I don't know. Open-source BME would be nifty, no?)

@adaviel, re: 12VDC chargers... Don't bet on it; it's reasonably likely to draw about 0.9 A. It's just too cheap to make a power-dumping passive regulator.