Battery drain display
 

Is there any way to calculate and show the rate of the battery drain?
Using xterm you can see the percentage of battery you have left, and if it also shows the exact amount of charge left in the battery then it would be possible to calculate battery drain..
That way you'd be able to see if your battery is draining too fast, or when you're low on power you can check and see how much you're spending and know how much time you have left approximately.

Re: Battery drain display
 

Unlikely. Battery is not linear enough to extrapolate to 1% or so and 5% means 20 steps, which, for 10 hour uptime at least means "average consumption over the last 30 minutes or so" which is pretty much useless.

Also, consumption in such a device is anything BUT linear. In reality, the screen eats depending on what was displayed (not backlight), GSM actually works via fast bursts, disk works async as flushed, CPU drains ROUGHLY with load, since different tasks that ceil the CPU drain differently - that's why there are testing-benchmark algorithms instead of loops. Wifi works in bursts, headphones eat with volume and signal, etc.

The only linear drain in the N900 is most likely the backlight.

This one of the reasons we use Li-Po in phones, they deal well with spikes. Unless one has an accurate, fast, hardware amp-meter, it doesn't work.

Estimated uptime left on mobile PCs is easier to detect because the drain is bigger in standby, because there are amp-meters built in in some of them and because miniature drains like bluetooth don't really count when you drain 150W with the CPU and 150W with the GPU.

If you try on N900, the variations in usage (popping the screen, changing songs) will throw your estimation off by hours, which is worse than just watching the battery IMO.

Re: Battery drain display
 

It doesn't have to be linear in order to show the current rate of battery drain...

Re: Battery drain display
 

Yes it would. GSM uses 2-3 milliseond pulses of varying intensity. One device in the phone can have as much as 50 times the average drain depending on conditions. The definition of "current" rate is very dim. It's very different from a light bulb.

You need to construct averages (software or hardware) and that requires hardware itself. Even if you try estimates by looking at the terminal running lshal every second, when you close the lid your figure just quadrupled. Simply moving around the phone varies recv signal and that affects tx signal. Older models varied emissions between 4 mW to 4W (I think that's been lowered since though). Signal strength alone can have a thousandfold increase over a few milliseconds.

Don't mean to be difficult.

I simply don't think it's doable with any useful accuracy.

Re: Battery drain display
 

Is there a current (amps) / power sensor in the N900's power circuit?

Even if it's not possible to predict battery time accurately, it would be great to have fast feedback on power consumption while running different apps, widgets, different network settings, mobile signal levels, etc.

Right now there's a fair amount of advice about what you have to avoid or disable to get good battery life, but some of it is guesswork. It would be great to have measurements. It would also help developers optimise their apps to reduce power consumption.

Re: Battery drain display
 

In screenshots of pre-release firmware, a Nokia Energy Profiler icon was visible.

On Symbian S60 devices, Nokia Energy Profiler can record real-time current measurements taken every 0.25seconds, among other things.

Unfortunately, NEP seems to be missing from production firmware and does not seem to be available anywhere.

Re: Battery drain display
 

For something not that accurate you could just poke at lshal | grep battery.reporting.current over a couple of minutes to get you your average drain over that period. then - now / timeperiod :)

Re: Battery drain display
 

Huh?
Poke what now?

Re: Battery drain display
 

mece: that would gate you average drop in voltage, not in capacity, those are mV not mW. As a result, it's not linear and can't be used to extrapolate something useful unless "something between 4 and 8 hours" is useful.

At this precision, one could look at cpu load, wifi, 3g and stuff and guess. However two people on 3G might get anywhere between 24h and 4 hours standby depending on signal strength.

I never said it can't be done, I simply said that it would be only marginally useful.

In theory, one could run the battery through an amp meter from a multimeter and profile it, then guess. But setting it down behind a metal beam could halve the time - only now the user has a 6 hour estimate instead of "40%-ish".

Then there's the temperature of the battery, performance, etc. There are reports of 25% error in battery charge level depending on various, deemed "normal" factors. (there's a bug about it, closed)

Nokia Energy Profiler for N900?
 

This really is a pitty...

Call to Nokians: Is there a version of Nokia Energy Profiler for the N900?
This would make it so much easier to estimate the hit of several options to power usage.
Right now I am using js.s's perl script to roughly my power usage ( http://talk.maemo.org/showthread.php...40&#post413740 ), although I modified it to run only every 360 seconds and started it into ther background. Nice script, but a proper version of the Nokia Energy Profiler would be great.

Thanks,
Corwin

Re: Battery drain display
 

doesnt lshal | grep batt do that already ?

it shows the remaining time left . or am i missing the point here ?

Re: Nokia Energy Profiler for N900?
 

Nokia Energy Profiler does a lot of other stuff too. I'd be interested to know if there are any similar suites for Maemo for the features other than power usage, such as recording CPU usage, transmitted and received data speeds and amounts, signal strengths and disk and memory usage?

Re: Nokia Energy Profiler for N900?
 

And does the script work? Can you get an estimate of time left on the battery?

Re: Battery drain display
 

There is an app called battery-eye in extras-devel. It's graphical display of your battery drain.

Re: Battery drain display
 

It must be possible! you guys are thinking to difficult here. it has nothing to do with all these things you are mentioning!

The n900 can get the current mAh every second or so. lets say you let the n900 log the mAh every second. so you can register how long it takes to drop 1 mAh lets say this takes on average use 30 seconds. then a fully loaded battery of 1320 mAh wil last 660 minutes. If the n900 takes this average every 5 seconds instead of 30 then you can calculate the exact amount of time left.

And offcourse when the time left is 660 minutes and then start dosbox it will be less. but if it updates every 5 seconds then within a minute the n900 will change the amount of minutes left to for example 60 minutes. when you close dos box it will rise again.

But i dont care!!! it would be awsome that when you are playing a game or browsing the internet, you can look at the time left and see how many hours you can play this game. or browse the web.

These values shouldnt be values of avarage use through the whole battery cycle but everages taken every minute. this way you can get an accurate battery time left on whats happening on the n900 at that specific time.

An average battery time is not interesting because it will never be acurate. but a battery time that gives the use of the mAh from the last 60 seconds will give a very tigh prediction of how long you can use the n900 till it dies out while keep doing the same business on the n900.

i hope everyone understands!

MAN!!! if i knew how to write code i would have built this allready. its so darn easy to make... but i dont know how to make an app. maybe someone else can make this.

Re: Battery drain display
 

Install kernel power (current version is 48), then search for i2cget in the forum. Those can provide time left as well as current usage.