Battery charge indicators are essential for maintaining the battery at a constant charge level. The over charging and undercharging of battery will shorten its life. So here is a simple battery level indicator circuit using Two LED's.
Click on the image to enlarge
In this circuit the red LED glows if there is a low battery charge and the green one will glow if the battery become charged. The core if this circuit is two BC 107 transistors. The transistor Q1 is in saturation under fully charged battery voltage. So the green led glows by completting the circuit while the red LED will not glow. When the battery charge falls below a particular voltage, the Q1 become cutoff and now Q2 become saturated. so the red LED glows. So this indiacates the battery has to be charged