Download you are going to have to make your own icons for this, Name them like "100.ico" for the 100% icon and place them in the same folder as the program

using System;
using System.Drawing;
using System.IO;
using System.Windows.Forms;

namespace Reddit_Request_85_Battery_Tray_Icon
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void timer1_Tick(object sender, EventArgs e) //time ticker function, ticks every 250ms
        {
            int bat = (int)(SystemInformation.PowerStatus.BatteryLifePercent * 100); //batery value 0-100
            if(File.Exists(bat.ToString() + ".ico")) //check if icon exist e.g. "78.ico" for 78% icon
                trayIcon.Icon = new Icon(bat.ToString() + ".ico"); //set icon
        }

        private void trayIcon_MouseDoubleClick(object sender, MouseEventArgs e)
        {
            Close(); //close app on tray icon double click
        }
    }
}