QUOTE(Eiraku @ Jun 29 2010, 09:14 AM)
Lol. Even if I have a 10000mah power pack, that does not change the the fact that most battery packs ONLY supply 500ma/5v through the USB port anyway, as per the specs outlined by the USB consortium.
As for the rest, it's a bit tl:dr (and I might be wrong about this) but here goes...
The mah does not determine charging speed, it's just an estimation of capacity at a given output IINM, which for most battery packs is 5v.
I'm gonna talk in MA now, and IINM, 1ma = miliampere so please convert accordingly.
Okay, how fast DOES the external battery pack charge an N900. From a full dead battery --> full battery (assuming the N900 is turned off), it should take 2-4 hours IINM. But that doesn't really matter, because the MAIN use of the battery pack in my usage scenario is to EXTEND N900 use time, which it does pretty well.
Okay the battery pack 2000mah, with simple calculations that should give the N900 2x the battery life. In practical use, power is also lost through the USB connection (it's not terribly efficient) in the form of heat and such, and that takes some of the power away.
Also, we must take into account how much power the N900 eats up and how much the battery pack can supply (which in this case is 500ma/5v). I'm assuming the N900 uses less then 500ma per hour (and looking at the battery and run time I'd estimate it to be in the vacinity of 200-350ma under full 3G load. 4 hours and 1300mah = 1300/4 = 325ma per hour).
That means that the battery pack is topping off an excess 100-200ma per hour (500ma supplied, +-300ma being used) and this extra power goes to charge the N900 internal battery. Also, the USB battery pack has limited capacity, thus under full load with the internal battery al 40%, the N900 will most likely drain the pack long BEFORE it can charge the N900 battery to full.
Take into consideration the AC charger supplies 1000ma/5v, that's an extra 600 frigging ma over worst case scenario use (300ma), which is why the AC charger charges the N900's internal battery so quickly. The car charger is also 500ma/5v but it's backed by your car engine = unlimited supply; in other words it's slow but will top up the N900 battery to full given enough time.
Thus charging up the N900 battery with a USB battery pack while under heavy load will be extremely slow, but it DOES extend running time of the device by quite a while, although less then the raw capacity would lead you to believe.
If you want it to charge faster, find a 1000ma/5v usb battery pack (google for Axim compatible USB battery pack) or a iPad compatible battery pack.
AND DON'T FORGET a dumb charger wire with the data pins shorted out (otherwise you're getting no more then 100ma, IF you get any power at all to begin with).
Or sometthing. My electro-speak is rusty lol.
don't forget reverse current. the external battery wont be able to discharge its entire contents. the n900 will push back once the capacity on both batteries becomes somewhat equal. so if had like 2000mah external battery, it will still have some power left, wont completely discharge.
the lesson here, dont always believe marketing specs. 2000mah might only just be 1500mah usable capacity.
anyway, when you charge from a computer. esp if the n900 is switched off, make sure in the computer settings in device manager > usb root hub > power management - disable the computer from turning off the usb port to save power. it will ensure continuous charge, or it will try to go to power save and turn off the usb port cos there is no data transfer while charging the phone when its turned off. the computer will see this as usb port inactivity and suspend it.
Added on June 29, 2010, 12:46 pmQUOTE(Eiraku @ Jun 29 2010, 09:40 AM)
Using 3G it will charge, but much slower due to increased consumption (read above). IINM consumption governs how fast you can charge, and the N900 (unlike the Axim and iPad) doesn't eat more then 500 ma at any given time (the Axim eats like what, 900ma?).
Again a larger mAh (or mah, or MAH) only lasts longer. It does not necessarily charge faster (unless it specifically outputs 1000ma/5v).
I do 3/3.5G while charging through the battery pack all the time. It just doesn't charge the internal battery that fast.
Which reminds me, does the DC-11 provide 500ma/5v output? I can't seem to find any data on that. Some battery packs are known to ONLY provide 250ma/5v = even slower charging (and in the case of the N900, no charging at all at full 3G load), and the DC-11 is well known to have charging problems with the N900 to begin with.
Also there's the problem of reverse trickle. Like water in osmosis, battery power moves from higher cap to lower cap, and that becomes a problem when the external battery pack is a extremely low power levels. For instance ext. batt pack at 10% and int. batt pack at 80%.
With modern power circuits, no reverse trickle happens (it's blocked), but the external battery pack no longer charges your phone.
And yeah, mplayer is not DSP friendly. VLC IS IINM.
vlc will suck your battery dry if you pause it while playing. always stop your videos.
This post has been edited by jananan: Jun 29 2010, 12:46 PM 
Jun 28 2010, 02:50 PM
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Nokia definately have to improve this aspect, I have the same issue on upgrading my old N95 firmware.
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