What about thinking about it this way?

If it was charging a li-ion battery (which is what? 97% efficient at taking a charge? It's one of the most efficient charging chemistries I know that much anyway..(wikipedia says 99.8% charge/discharge efficient)) at 1C. We'd all have full batteries in just over an hour. It always takes my battery from flat a good couple of hours plus (2.5? guessing..) to be fully charged? That wouldn't be happening if it was charging at 1C, 0.5C yes.

>> added info:

Since writing this post I did a little experiment. When it's happy my phone idles at 8- 9- and 12-13mA through the powermeter.sh script.

Using a Fluke 111 to measure the current through the AC10u charger I am getting 642-648mA. With the current I am getting around the same. Taking in the 12mA standby current there is about 20-30mA difference between the two readings. That is, between what the current reading from the powermeter.sh script says and what the Fluke 111 offers up. Incidentally the built in current monitor appears more finely grained and is reading those 20-30mA more than the Fluke meter. An aside, I altered the powermeter.sh script slightly to reflect the bq27x00_battery kernel appears to reading out correctly in micro amps now (uA).

The current measured by the bq27x00_battery module does not change more than 4mA or so when the Fluke meter is present. So the current shunt is very low resistance.

>>> MY CHARGER IS FAkE

I just tried the other AC10u charger we have here and it provides a more healthy 830mA at the State of Charge the battery was in. The current was tapering down so indeed the original OEM Nokia chargers could possibly provide a full 1A when the battery is fully flat

Cellphoneforever (a notorious ebay seller):
So-called NEW (actually refurbs) N900s with the following:
- Send the phone back with no tracking when the phone needs repair (then they say it got lost in the post)
- Keyboard is fake (non-OEM) The keypad is wears out.
- The battery fake
- And now, found a fake charger! There is very little to distinguish between the fake charger and the real one other than the lead is slightly more heavy duty and slightly lighter in colour and more "rubbery"