Notices

@shadowjk:
You are correct. However, seeing as the coulomb counter is always off to some degree, I assumed it's just a guess based on voltage.

That would fix some of the issues (with droop). Unfortunately, it still goes up and down (looking at battery-eye) wit at least temperature and SOME droop.

Judging by the attached thanks I'd say several people understood the geek terms. Looking back, I don't really see big words. Volts, amps and watts (one watt is one volt multiplied by 1 ampere for DC (W = V x A) I see interpolation. This is as simple as I can put it, it is a technique by which samples that are unknown are guessed. And it is not a geek word. "Curve fitting by regression analysis" is.

Ooooh, you mean like this:

I get 96% full charge, and live out 24 hours normal usage. That's 96/24 = 4. That's 4% an hour. Ten hour trip, 40%. Stop there or it dies out. I do this manually, by brain, because an app can't know I still have a few calls to make.

Finally, I noticed you dismiss people helping you as geeks. I will not comment on the intention, but on behalf of all the geeks here, I'd like to say thank you.

Nothing crowns 25+ years in schools and universities, all the effort, all the frustration, time spent in hospitals due to high stress, like being spotted half way across the globe, through a forum, by a person who thinks your best whack at simplicity is a geek attack.

You, sir, have made my day.

You have no access to the coulomb counter from standard maemo 5.

The stuff in lshal / hal-device bme is something else, and probably in part based on voltage, and relies heavily on the battery being within spec, which it wont be after one summer's use (batteries hate heat)..

Lol pwned....

Complaining about and insulting the people you want to help you probably isn' the best way to go about getting them to write an app for you.

I can't do it anyway, but if it were me, what I'd want is an active vs idle estimates. Since it's pretty clearly been explained that trying to get accurate values for the N900 is pretty much impossible, here's what I'd do.

Setup the app with a database, poll 1x a minute (or less) for battery info and load, throw out any "charging" values. Now average the values in the database up to 14 days where cpu load is less than 25%. That should give a pretty good estimate of your own personal idle usage (based on widgets, connectivity, etc that is all unique to your setup). Now go back and average the numbers for any data point where cpu load is over 75%. That and battery info should give you another estimate for active usage. Average battery info for the last 5 minutes (to even out spikes) to predict the current battery state. Divide that by your idle / active use numbers to get your idle / active time left. Update that info either on demand or after a set time period.

Make all the numbers user tweakable, and you'll end up with an apt / script that won't be really usable for anyone, and a ton of complaints about how far off it is.

All you'd need is a script to add values to the database, set alarmd to run it every so often, and a script for one of the desktop widget to run on click and there ya go.

Just for the fun of it: here's a python shell script that prints a single number estimate in hh:mm. If no estimate can be generated, it prints 'n/a'.

It assumes you have battery-eye installed. (It takes charge data from battery-eye's database)

run with:
It's .txt, because tmo didn't allow .py extension files to be uploaded.

It's likely to crash, burn and eat your children. Feel free to improve. Post back results and/or improvements here.

License: public domain

Edit: I won't bother to give any support for this, "use the source Luke".

I used to have iON Battery timer on my E71 which was really good at predicting battery time an percentage remaining.
I think it used memory of past battery life as well as remaining battery voltage maybe? Am don't how it worked for sure but it was excellent and would be great to have on my n900!

You should take that up with battery-eye's coder, it's darn near perfect in what it does, and maintains a long database (trimmable to 28 days), on which you could easily run statistics.

In theory, detect end of charge state (such as, charger connected, but voltage drops, meaning it stopped). Unfortunately, you'd need a shutdown condition (battery at 0% and then a reboot) in the same day (well, continuous) to profile the battery. You can't have midday charging.

OTOH, a pen and small paper does just about the same by looking at battery-eye graph.

with looking at previous consumption will give you 0 result.

If you really want to make something like this you need to monitor the mah every few seconds and calculate how many mAh are used in a specific amount of time. with these facts you can calculate the remaining time left on that perticular use. when you start browsing the web, the amount of mAh used per minute is going up and the estimated time left is going down giving you half the time it did before you started the browser.

Some people say this is useless because it drops when using somthing and goes back up when going in idle mode after. but still it will show the exact time the battery will be emty when for example playing angry birds. the cpu will use an amount of power the program calculates the average per minute that minute and echo's a calculation of how many minutes that will last before the mah runs on 0. when you stop the game and go in idle the average power use per minute drops drastically. and the program will yet again show how many minutes you have left when being in idle.

Example.

on start we have a n900 with 1000 mah left in the battery.
the idle state of the n900 consumes 1 mah per minute, the output of the program should be 1000 minutes

so this wil give the n900 1000 / 1 = 1000 minutes
1000 minutes / 60 = 16 hours left

when starting angry birds the n900 will consume an average of 10 mah per minute.

so this wil give the n900 1000 / 10 = 100 minutes
100 minutes / 60 = less then 2 hours

And the indicator will indeed go up and down. but thats understandable! i just wanna know how long i have left while doing a specific thing with my n900 like playing a game.