there allready is a howto @ wiki

http://wiki.maemo.org/Make_your_battery_last_longer

I will edit the article today, it doesn't seem to include everything mentioned here.

not related to making the battery last longer, but in regards to charging.

I found the N900 charges WAY faster when you turn it off, im talking a dead battery to full in like an hour or 1.5 hours. can't remember exactly because i didn't time it, i might have played with it for half an hour hooked up, but i just know it was super fast and the battery was so dead that it turned itself off

That's crossing my mind too. If packet transmission or waking up the 3G radio is a significant power drain, I'm wondering if there may be a market for an app+internet service combo which combines the pinging traffic for all the different IM services, Facebook widgets and so on into a single low-rate keepalive stream, to a server which fans them out.

It's a bit inconvenient if you have to reboot the phone every 7 hours to swap a battery, isn't it? Especially with all those lovely "always on" chat windows one no doubt has open all day

does it help to have one of those desktop reserved to have NOTHING on it (ie no shortcuts, widgets and apps)?

so when you dont use the device, you switch to the desktop that has nothing on it to let it idle on that desktop.

does it help to extend battery life (you know, because its not actively rendering stuff)?

Well this option (changing battery) is better than no option at all. Don't you think?

http://www.latimes.com/business/la-f...,2546606.story

Doesn't seem much different from how I get the most out of my laptop battery: disable power-using features when I don't need them. I lower brightness, disable bluetooth, put the wifi in power saving mode, etc. on my laptop too.

Many people have reported battery time on low or moderate usage to be less than 6 hours. I have experienced same, but have now isolated the problem and will explain here a way to get battery to easily handle a few days of low usage.

The problem is Wi-Fi. For some reason N900 doesn't recover from having been connected to Wi-Fi and will keep eating loads of battery even after closing the connection. Only restart will help. Simply searching for Wi-Fi without making actual connection doesn't trigger the bug for me. (The phone searches for Wi-Fi whenever you manually start any internet connection.)

So, do not use Wi-Fi unless you want your battery to die fast. Or reboot after using it. This is until a real fix comes for the problem.

With this fix I managed to get my idle battery time to increase over 30 times! (From bellow 7 hours to over 9 days.)

It seems some people do not have this problem with Wi-Fi usage on their N900. It may be related to encryption method used or the Wi-Fi router connected to. In any case, some circumstances trigger a bug in N900 causing excessive battery drainage even after having disconnected from Wi-Fi. And the issue is fully reproducible. So, if you get it once with given Wi-Fi connection saved, you will get it every time unless you change some settings elsewhere than on the phone. That is, until the real bug has been fixed.



I had first experimented with various other things and have found out that normally there is no battery drainage problem with following things: Calendar widget, media player widget, foreca weather widget (only manual update), location widget and alarm clock. Also keeping terminal window open on the back doesn't drain battery noticably.

Wi-Fi tests were done with following settings (no problems prior to activating Wi-Fi connection for first time after reboot):
- Ask when needing connection.
- Dual GSM mode (uses 3G here at all times, 3.5 G when there is data activity - signal is a bit weak but doesn't matter).
- Widgets: Calendar, media player, foreca weather (only manual update) and location widget (on other than the viewed virtual desktop)
- Software: X terminal on background; Custom programs installed: OpenSSH client.

I did some experiments about battery usage on different cases. Prior to testing I rebooted the phone and kept it at idle for 20 minutes to let the battery voltage stabilize after the booting load. Results:
Idle without having used Wi-Fi: 54 mAh usage in 9.3 hours -> 5.8 mA.
Idle with 3G internet connection idle: 32 mAh usage in 1.9 hours -> 16.8 mA.
Idle after connecting and manually disconnecting from Wi-Fi (10 mW): 183 mAh in 1.0 hours -> 183 mA.

The difference is huge. The fully charged new battery charge is 1267 mAh, so idle 5.8 mA usage gives about 9.1 days, idle with 3G internet connection idle 16.8 mA usage gives about 3.1 days and idle after connecting and manually disconnecting from Wi-Fi 183 mA usage gives 6.9 hours. That is over 30 times the increase from idle to Wi-Fi bug triggered idle. And still over 10 times the increase from idle with 3G internet connection idle to Wi-Fi bug triggered idle.

The test times are high enough for accurate results and as such, it can be safely said that the Wi-Fi bug makes a really huge difference to the battery time.

I also tried to test having the Wi-Fi connection on but idle at 10 mW for an hour, but the phone had automatically disconnected it at some point. The resulting usage from part idling Wi-Fi 10 mW connection and rest pure idle with battery drain bug activated was about same as the 183 mAh an hour from previous test. Thus, there is no way to avoid the bug opening a Wi-Fi connection triggers as of now. At least unless some other connection setting than ask when needed keeps the connection alive.

If you want to test out these things yourself, here are some hints to use:

On terminal, you can get good information about battery status with command "lshal|grep bat". It will include some unnecessary information as well, but for advanced usage I recommend following aliases (save to ".profile" file on home dir to get them automatically for new terminal sessions):
alias g="grep"
alias gv="grep -v"
alias battery="lshal|g bat|gv nf|gv pr|gv yp|gv un|gv is|gv lc"

And then to check battery level I use "uptime;battery" to get both current time as well as battery information. Then keep the terminal on background to see both old values as well as new values. Do note you can scroll the terminal text to see backlog.

I'm still seeing heavy drainage with 10mW power setting. I plan to turn off WiFi for the rest of the day, and restart to see how my battery fares.

I already ordered a spare battery though.

I heavily doubt this is the reason for fast battery drainage.

I had my n900 connected to Wifi for more than a day now without charging it and without a reboot so I cannot confirm this

my battery uptime is 2 days 48 mins now and it's still running at 47% according to the tools you've mentioned.