Find out battery charge capacity in percentage using C# or .NET

Don’t have a laptop to test with, but I’m guessing you could use the WMI class Win32_Battery.

It has two fields that look interesting – DesignCapacity, which tells you

Design capacity of the battery in milliwatt-hours.

and FullChargeCapacity, which has the fascinating note that

Full charge capacity of the battery in milliwatt-hours. Comparison of the value to the DesignCapacity property determines when the battery requires replacement.

So my guess is that you can use WMI to read these two values, and then calculate FullChargeCapacity/DesignCapacity to find the battery health percentage number.

EDIT

Here’s a brief example of accessing WMI information using C#. I first added a reference to the System.Management assembly. Then:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Management;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            System.Management.ObjectQuery query = new ObjectQuery("Select * FROM Win32_Battery");
            ManagementObjectSearcher searcher = new ManagementObjectSearcher(query);

            ManagementObjectCollection collection = searcher.Get();

            foreach (ManagementObject mo in collection)
            {
                foreach (PropertyData property in mo.Properties)
                {
                    Console.WriteLine("Property {0}: Value is {1}", property.Name, property.Value);
                }                   
            }
        }
    }
}

Also, note that you are basically running a SQL-like query against WMI, so you can vary that if you want. Windows Management Instrumentation Query Language, or WQL, is what you want to search for to learn more about it.

Also take a look at ahawker’s answer, it may end up being more helpful if WMI isn’t properly capturing the battery data, as he notes.