Controling the N900 Hardware Battery Charger
 

So I have this problem. I have a Nokia N900 which software seems to be very much screwed up. My goal is to flash it. To do that I need to charge the battery fully. Due to the ruined OS I can't charge it. I'm sure that it's not a hardware bug because when the battery is so drained that it can't boot the hardware battery charger takes control charges it finely up to the point where it wants to boot or whatever and it stops charging. What exactly happens when it charges to the boot point is: the led starts slowly blinking in yellow for about 3 - 4 times with the NOKIA screen without the light being on. Then it just shuts down and nothing happens. From this point I can boot it up but even booted up it does not charge with a usb charger with which I charged it in the first place. When I hook it to my 32 bit win 8 pc the pc keeps saying that an unidentified device has been found and then that it is disconnected and then that it's found again and again disconnected and so forth. I can do whatever with the turned on phone but for a very short while since it has very little energy in it. At one point it recognized the charger as a connection to a pc...

What I want to accomplish is to somehow make the Hardware Battery Charger to charge it to 100% so that I could flash it. Is that possible?

Re: Controling the N900 Hardware Battery Charger
 

Old nokia dumbphones are good alternative chargers for N900 batteries. There were somewhere a guide to recover flat battery only with N900, but I cant find it now. It involved maybe removing and replacing the battery from the phone maybe while connected to charger and then leaving it for several hours.

Re: Controling the N900 Hardware Battery Charger
 

Well what I do have available is an N73 lying around on my table but I don't think that I could use that to charge the N900 battery ofc maybe that guide has some clever plan of some sort.

Hm... Now when I think about it. Maybe the software BME is screwed up and that's why it's not charging?

Re: Controling the N900 Hardware Battery Charger
 

You can check if the N73 battery has the same voltage (3,7V) as the N900 battery and the same pins/contacts (+,T,-). If it does, just connect the N73 battery comparment contacts/pins with wires (avoiding short circuits) to the N900 battery according the order of the +,T and -. Then just plug the N73 to its own charger and voila. the charging circuitry monitors the charge level by the voltage, so it doesnt matter that the batteries are of different capacity as long as the nominal voltage is same.

Re: Controling the N900 Hardware Battery Charger
 

The N73 does have the same voltage (3.7V) but the pins are +, nothing (I suppose this is "T"), - while the N900 has +, -, T (nothing again) if I understand the marking properly. Maybe I could just connect the wires on my N73 pins and simply switch the T and - outputs to the N900 battery and it would work?

Re: Controling the N900 Hardware Battery Charger
 

I have done these connections only when there was the T-label present at the third terminal. By looking at the data at http://www.cpkb.org/wiki/Nokia_N73_pinout it seems that the unlabeled is NOT the thermistor but "battery size indicator" - whatever that is. So I think it is not suitable for the N900 battery. Sorry.

Re: Controling the N900 Hardware Battery Charger
 

Eh damnit. Well thanks for the help though I'll look for an alternative on how to charge the N900's battery. I wish I could make its emergency charge charge the battery to max somehow. It would be slow (100mA) but at least it would charge.

Re: Controling the N900 Hardware Battery Charger
 

I reread your first post and got to thinking, that have you considered that this might also be a connector problem, because I think that the PC should recognize the device correctly regardless of the charge state. And the fact that the phone mistook the charger for PC, it could mean that the connection in the either part of the usb interface could be damaged. If it is the charger or the usb cable you are using, then you're lucky, but if its the phone then there arent many options left. There is long thread here about the usb-connector coming loose from the phone. You could try to charge/connect to pc using different cable and see if it works. You could also checkt that there isn't any foreign material or dirt in the phone side of the connection. Broken connector on the other hand would not neccessarily explain the fail-safe charging to the boot point and then nothing.

Re: Controling the N900 Hardware Battery Charger
 

I can assure you that the usb port is fine on the phone. Yes, the phone had a broken usb before but it was replaced and everything was fine up until it received an os update and everything went bad, restoring factory defaults and even clearing data didn't fix it. The USB cable I'm using to charge and connect to my pc is from my LG Optimus L9 and it is perfectly fine. My pc most likely doesn't recognize it because it had never seen this phone and the booted phone doesn't like seemingly everything that is connected to the usb so it doesn't have enough time to install the drivers and stuff. I also did check for dust and/or dirt REALLY closely and didn't find much either.

I might give Nokia 5330 a shot at trying to recharge this battery it's pinout seems to be the same even though it carries a different battery.

Re: Controling the N900 Hardware Battery Charger
 

I have had two(!) USB cables exhibiting connection problems. Both worked for a while, then worked only for data, but the phone would not charge through them, then lost connection altogether. How can a cable break is a mystery but they do.

The upshot is, try a different cable.