This LED gauge shows the charging level of a single cell 3.7V lithium battery.
The 5 different levels are as shown on the picture.
Therefore, each level equals the following cell voltage:
100% : >3.9V
75% : >3.7V
50% : >3.5V
25% : >3.3V
If the voltage is under 3.3V, only the red frame is lit.
The dimension of the display part is 31 x 20mm, the length of the PCB is 45mm. The diameter of the mounting holes is 2mm.