I charged my n900 when the battery level is red and I charged it for around 3 hours already and yet it doesn't show battery full yet,it was weird because previously the charging will be completed after around 2 hours of charging but this time after 3 hours the yellow charging light is still blinking so I decided to turn off the wall charger and found out that the battery level were the same before I charge it, still low,so I take it for another charge and this time different things happened,again I turned off the wall charger after 2 hours and 30 minutes of charging the battery level is full this time but the yellow light keep blinking, why is this happening ?

• What sort of charger were you using? did it have the correct output wattage? In the first instance it doesn't sound like you were using the correct one or the genuine nokia charger.
• Is this device overclocked and/or laden with plenty of widgets/programs running in the background?
• Are you using maemo OS or is this some other OS such as nitdroid/meego? This question may not be relevant but if you tried other operating systems during its charging phase have you tried charging normally with just maemo OS?
• Are you running some third party bme script or alternative bq27200 kernel module? If so have you tried nokia's BME instead?
• Are you using some other battery? like a none genuine nokia N900 battery? Do you also have weird battery hacks like 3000+mAH battery setup?
• How old is the battery and have you tried other batteries (preferably genuine ones)?

Loose USB port is a possibility :/

you think you have a charging problem ? how about this.

stock standard n900, all legit updates and no flashy firmware or software. regular usage for 2 years.

about a month ago i noticed that the battery, the one that came with it back in 2009 was only charging to about 85%. as soon as i would take the charger out it would drop a few % very quickly to about 80% and then be normal for the next few days.

so i bought a new battery. charged it for 48 hours and checked it. 85% charged.

i have tried charging while 'off' via usb and power, and while on. 85% max.

i suspect that something has happened to the charger inside. i suspect if i put either battery in another device and charge it will be 100%.

anyone have any ideas ?

The defaut battery meter can do that even with brand new device and brand new battery.

Additionally the "Battery Full" notification seems to run independently of both the charger and the meter. That is, it might still be charging when it says full, or it might have reached full hours ago.

The battery meter is totally reset on each boot of the phone, starting from what's mostly a complete guess about the battery state.

I would just treat 85% as the new 100%. The numbers from the default meter don't relate much to actual battery capacity anyway, except in the sense that it counts down in a roughly linear direction when not charging

ive been using battery graph since it was released and it has been very accurate stats wise... hence why i noticed this huge change. the first bar (although there is 8) would last for 12+ hours and then would drain nicely over the next 48 hours. solid performance.

i am sure that my original battery was still pretty good and had only lost a little charge. but since it stopped charging to 100% and wont charge a new one to 100% i am a little curious. i charged the same battery in another device and put it in my n900 again and it shows 100%.

the n900 is faulty.. but when i get my n9 sorted ill back up my n900 and flash it clean (both) and see what happens. if it still doesnt charge 100% then ill say its a hardware issue.

Same problem here (since a few monthes, but never reflashed since then).
I add a few more details hoping to involve more people.
What happens is that the lower the current used to charge, the higher the percentage of charge reached BEFORE the red led
blinks and the charging process stops: i.e., charging with wall charger leads to 80% (battery charge), with usb port 70%.
After a few experiments I am now able to fully charge my mobile. I had to install i2c_tools and a slightly modified (by
me) version of joerg charging script. The modified script stop BME, loads the appropriate values on the bq 24150 charging
chip and keeps it away from being watchdog-stopped by resetting it's internal clock every 15 seconds (but doesn't read
any of the bq27200 values).
I can guess that when the problem occurs the bq27200 fails somehow, and any attempt to read it's values (battery temperature, charge percentage, etc...) leads to a fault. In fact, with the battery fully charged if the script gets stopped and BME gets started the phone will struggle, suddenly becoming unresponsive, and I guess that the problem is due to BME trying to read bq27200 values but not being able to.
Fortunately it looks like bq24150 keeps working properly, though ensuring a proper and hopefully safe charge.
I have to say that I had big problems with my phone, since it loose the phone signal probably after an heavy rain. It was then repaired by a third part technical center (since Nokia refused to repair it). The battery issue strted a few weeks after the phone was repaired, so it might be related (but it might be not...).