Measure. - Here is Circuit Schematic Low Voltage Battery Level Indicator using LM317 Voltage Reference with detail discuss. Up to now, this battery level indicator design was limited to 12 & 24V applications. In past circuits, the use of fixed resistors greatly simplifies setup. However, fixed resistors resulted in application inflexibility that precluded use at lower voltage and different types of batteries. In the updated circuit, all thresholds are set via potentiometers, and an LM317 provides a 1.25V voltage reference. Rather than lighting LEDs progressively, this circuit blanks low order LEDs thus reducing power consumption. While the comparator and op amp operate as low as 2V, the voltage reference requires 3V (as a 1.25V reference). This easily accommodates 4.5V battery applications, but is far too marginal for 3V applications. By following the application information indicated on the schematic, it may be extended to 28V.