Checking Battery Capacity in Windows 7

Alternatively there is a Free software to measure power consumption by Microsoft Research.
It is called JouleMeter.
Find out more about it here.

A new feature in Windows 7 is the ability to check battery capacity.
Take a look at the following:

Open a Command Prompt Windows with Administrative Permission
Enter:
powercfg /Energy

It will create a report in
C:\Windows\system32\energy-report.html

There is one line like this

Battery:Battery Information

Battery ID	11121SANYOAS07A31
Manufacturer	SANYO
Serial Number	11121
Chemistry	LION
Long Term	1
Design Capacity	48840
Last Full Charge	41214

The amount of battery life left can be calculated by

eg. 41214/48840*100

Formula:  (Last Full Charge)/(Design Capacity) * 100

Which equates to 84.38% meaning my laptop battery has only 84.38% of charge left (because I didn't take good care of it. There was a few times when the battery was almost fully drain)

So make sure you switch off the laptop or connect it to an AC outlet when battery life reaches 10% and do not expose it to high temperatures.

Alternatively you can download the new HWMonitor as it reports the charge capacity directly.