i have a problem.... my n900 is consuming about 30%battery @ reboot

for exsample.... i have about 60% battery left then i have to reboot or my n900 crashes and reboots and then my battery is almost empty....

this week i was listening musik.... and i had about 50% left... then i accidently turned of my n900.... startet it again.... and then it said battery empty....

about 10 min ago it crashed.... before the crash i had exact 69% and then after reboot i have only 15% left....

i dont think it is my battery because i ve 3 batteries and with all of them i ve the same issue....

thx for hlp...

greetz

top in xterm is a good start for battery issues, will give you an idea of whats sucking battery life

the nokia BME is inaccurate. After a while you might notice your battery suddenly go up.

Last weekend I had 15% battery remaining when I left home, 2 hours later I had 18% remaining. Whaaa? :P

If you install H-E-N and run it, it stops BME. Upon exiting H-E-N, it restarts BME. You can see the battery level change wildly every time.

This is a symptom of a battery starting to get old. Its inner impedance is increasing, and the reboot sucks more current out of the battery than for normal operation. What this translates to is that the voltage will drop a lot due to the extra current drawn during reboot. A new, healthy battery can handle that with ease (less internal impedance) and only drop a little bit. An old battery can get floored. It will recover after a while (because the current drain stops when the reboot is finished), but if it's bad enough the voltage will drop to a level which can't sustain the device. So you can only reboot when the battery is fully charged.

The only remedy is to go out and buy a new battery. Which sometimes can be easier said than done - most of what you find in shops are old (been on shelves for years) and stored in non-optimal conditions, e.g. too hot.

and just want to throw it in here, go to my battery thread for the current buyers guide.

of course i have no info on supplier's battery shelf time

what about something like the memory effect?? like loosing capacity with time....

i had the issue when i bought not original batteries they the capacity was high... and after a few months it was reduced.... so the battery didnt last long ...

do liion batteries have that too??

sry for my bad english....

Memory effect does not apply to Li-Ion batteries.

However, low quality batteries and mistreated batteries of any kind can quickly lose capacity.

Hey phoenix,

The reason this happens is a little complicated.

It's very difficult to estimate the amount of energy left in a battery. You can measure the no-load voltage, or a voltage under a known load, and based on that make some intelligent guesses, but they're always just that.

In the case of the n900, the BME monitors voltage and current draw over time, and integrates the values over time to estimate the instantaneous energy remaining. The BME uses some facts to aid it: fully-charged battery capacity, known discharge curves, temperature, etc.

When you reboot, the current draw spikes dramatically, and so drops the starting voltage (higher draw = lower voltage), so the initial estimate is much lower.

What you'll find, though, is that it doesn't actually make much of a difference in run-time. That last 20% will take nearly as long to discharge as the 50% it was previously reporting.

It's a difficult problem to solve, unfortunately.

hmm...
first of all... thx for the answeres....


would it help when i plug in an charger to support battery (and maybe prevent voltage drop)??

i am 5 days in the wood with the austrian army...
i think best would be not to reboot my n900....
but what when i have to reboot??

i ve 2 full charged batteries ... and a raikko Accupack 5200.... thats an 5200 mAh battery i use as an charger....

is it bettter to charge often an not so long.... or should i let the battery run out every time.??

Definitely better to minimize the depth of discharge; charge early and often.

You could also consider the Mugen battery; it's almost double the capacity and is one less thing to carry around.

Don't worry about rebooting... it only uses maybe 10-15mAh (out of 1320 in a standard pack).