N900 Hardware Charge Meter
There is a largely unused charge meter chip in the n900, a TI BQ27200.
It does not function properly in normal use with the stock BME as that usually turns off the phone before the threshold which would enable the charge monitor to properly learn the battery capacity.
In many phones, this chip would be integrated into the battery, which has a number of benefits, from more rapid temperature sensing of potentially dangerous conditions in the battery, to being able to swap the battery, and have the swapped batteries charge accurately measured instantly.
The n900 integrates this chip onto the motherboard.
With a replacement BME, it can learn battery capacity, and be used for useful life predictions.
It also can be used for energy profiling - see [[1]]