BatteryCat is a battery monitoring and health tool, it show Current Battery Change, Maximum Battery Change, Additional Info includes Changer connected (yes/no) and Battery is being changed (yes/no).

The main window is split in three sections (from top to bottom):
1. the current charge state in relation to the current capacity
2. the current capacity in relation to the design capacity
3. information about the current power state

History Window
When clicking on File/History (CTRL-H hotkey) the History Window open next to the main window. You can see the recent saved capacity values.

Options Window
Clicking Options/Options in the menu bar opens the 'Options" window. The hotkey is "Ctrl+O".

Custom Battery Capacity
BatteryCat may fail to read the design capacity from the battery. In such a case you may enter the design capacity manually. Note that you have to check the "Custom Battery Capacity" Checkbox first.

Polling Interval
This defines the time after which BatteryCat reads the current values from the battery. The default is every 10 sec.

Clicking 'Save' in the options panel saves the options to the BatteryCat config file, which is: %USERPROFILE%\batterycat\batterycat.ini in Windows and $HOME/.batterycat/batterycat.conf in UNIX/Linux.

Background information:
Each battery has a certain 'design capacity' i.e. it is designed and manufactured with a certain capability of storing electrical energy. When your computer runs off the battery electrical energy is retrieved from the battery. At some point most energy is consumed and the battery has to be recharged. Recharging simply means that electrical energy is put into the battery for later retrieval. Unfortunately the charging/discharging process is not ideal such that (and due to other reasons) the usable capacity declines with time. With older-generation NiCd and NiMh chemistry the number of charging cycles often was the limiting factor for the battery life time. With modern Li-Ion and Li-Polymer batteries the number of charging/discharging cycles is not so prominent any more. But still batteries loose capacity with aging. Aging is fastest when the battery is fully charged and at elevated temperatures (e.g. when you have it in your laptop and mostly work off AC supply ...)

The battery capacity is often expressed in mAh (1000th of Amperes times hours), or sometimes in mWh (1000th Watts times hours). 1000mAh means the battery can supply the current of 1A (1000mA) for one hour. Depending on the model and application laptops draw about 1.5 to 3A current from the battery. So you can estimate that a 4400mAh battery can supply your laptop with energy for about 2 hours (or more or less, depending on your computer model).
BatteryCat not only shows you the current value of the capacity but it also lets you create a history so you can monitor the development of your computer's battery.

Requirements:
* GTK+

With GTK+, BatteryCat now supports the following platforms, Linux, Win32 (NT branch), FreeBSD and Mac OS X.

The license of this software is Free, you can free download and free use this system monitor software.