zimon | # 21 | 2010-03-28, 21:28 | Report

Well, the subjective fact still is, that my laptop's battery "died" in less than a year, when I used it it like with "the HIGHEST COMFORT" for me and keeping it connected to wall power input when at home.
If I would had taken the battery out always at home, I still would have a mobile laptop, but now it is just a laptop without real mobility.

So, for N900, if it is possible somehow by software, it could be good if at home (in the evening) I could attach it to the USB-bus, and when the battery is fully charged, I could detach the battery on the fly and put it in the fridge for next use (next morning) , but N900 would stay ON and would get its power from USB still.


Taking the battery from the fridge next morning when I am about to leave, would be as much more simpler and quick (15 secs) than changing the clothes after the night or brushing the teeth.

Yeah, everything is kinda integrated in a mobile phone. The question still is, is there somekind of software interface to this power system, which could enable the above wished use case.

zwer | # 22 | 2010-03-29, 00:13 | Report

Don't hold me on this one, but I think that the N900 stops charging of the battery once fully charged and resumes charging after a while when there is a significant drop in the current bat. level.

1) I've noticed several times for it to start charging (shows that `Charging` bar briefly) after a prolonged staying on the USB.
2) In dependence on when you disconnect it from your USB there will be a different charge level, dropping all the way down to 90%. Usually, when you disconnect it right after it reports `battery full` you get 96-98% charge.
3) After fully recharged and staying connected for hours, if you disconnect it and immediately reconnect it, it will start recharging even tho a second ago it was reporting `battery full`.

So, based on that I'd assume that there is indeed a blockage of constant mini-charges. It stops charging once the battery is full, and resumes when the battery charge drops to 85-90%.

However, keep in mind that while there probably is a system to stop mini-charges, there is a key difference between a laptop and the N900 - N900 never runs on the USB current (500mAh is not enough juice for its peak usage) - it runs from the battery at all times whether connected to USB or not, and if you set a heavy computational task that will eat way more current than the USB can provide - you will never recharge your battery. Or if your phone is `idling` at around 500mAh, the charge cycle will never complete thus effectively eating through the battery.

However, keeping it connected at all times while not doing anything on it is probably safe - if you don't have many background processes N900 will stay in a deep-sleep state where it will drop only few percents per hour, thus kicking the mini-recharging (if the assumption on 85-90 range is correct) at most several times a day - let's say 4 - that makes at worst `wasting` one recharge cycle in 2-3 days, and with avg. of 1000 recharge cycles you'll probably get rid off the N900 before you experience a significant battery degradation. Of course, if you are doing several full recharges a day, that's a whole other thing, keeping your N900 connected to the USB is not likely to destroy your battery in a perceived life-time of the device.

shadowjk | # 23 | 2010-03-29, 04:52 | Report

You're absolutely right that it stops charging once full. It's pretty rare to see it reannounce charging as you've seen. I'm guessing it only does that if charge level has dropped significantly (say to 75%?) when connected to power.

ossipena | # 24 | 2010-03-29, 04:57 | Report

two points:
1.
what is a price of bl-5j?
what is a price of laptop replacement battery?

2.

what is usage time change with 5% drop?

if laptop stays on approximately 3 hours and N900 10+ hours, the 5% starts to matter.. so imo the charging chip has a good compromise between battery life and usage time when trickle charge prevention limit is somewhere around 80%.

zimon | # 25 | 2010-03-29, 13:12 | Report

That is a good point, that if USB from PC cannot provide more than 500 mAh, N900 still has to use some current from battery when CPU is busy. However, some USB hubs/ports provide more than 500 mAh and N900 can correctly request this when the USB is connected.

So the prolong-your-batterys-life-application should tell then how much power it gets from the USB-bus and when the battery is fully charged, tell if it is possible to detach battery or not on the fly.

Good N900 battery is not cheap. The original N900 1350 mAh battery IMHO is almost useless, but this Mugen Power 2400 mAh battery, which I am now using is almost us$90, but well worth it because I can use anything I want (except perhaps to play Quake Arena 14 hours) and single full charge will last the whole day, which was unprobable with the original battery.

So I wouldn't mind to detach the fully charged battery and keep it in a fridge when I am at home and N900 is connected to USB.

zwer | # 26 | 2010-03-29, 13:35 | Report

Whether you'd mind removing the battery or not makes no difference. N900 will never use the direct USB current, no matter of how much power is available through the USB cable - standalone charger provides, IIRC, 1200mAh after all... If you remove the battery, it will power down. That's its hardware design (for several good reasons) and cannot be changed by software.

zimon | # 27 | 2010-03-30, 16:19 | Report

When these mobile phones have become more and more personal computers (N900 is, if not more), I think above mentioned use case should be supported. If the device is connected to PSU which gives enough power, battery could be hot-switchable and also the device could be run w/o battery.

zimon | # 28 | 2010-12-07, 23:39 | Report

Has there been any changes to above facts?
The situation haven't changed with kernel-power and h-e-n?

What I still like to do, is always connect my N900 via USB-cable to PC when at home, so it would auto-sync and charge the battery. But I'd like to keep it connected to USB until I leave home, so often it would be 8 - 14 hours connected daily and sometimes 48 hours connected to USB.

a) How does N900 behave with these new kernels and drivers when connected to USB after battery is fully charged,....and b) if USB-host which it is connected to can provide more than 500 mA?

zimon | # 29 | 2010-12-08, 21:25 | Report

Also, the fact that N900's CPU is running at 500 Mhz when it is connected with USB, is keeping me from using "the N900 so that its the HIGHEST COMFORT for you".

What is the reason, it has to be locked to 500 MHz when connected to PC with USB? Is there any way kernel-power could change this?
One can see, I have had N900 connected to USB quite alot.