Only certain battery voltages exist, because this voltage depends intrinsically on the battery's chemical composition.
learn.sparkfun.com/tutorials/battery-technologies/all (CC BY-SA) has a very good summary list, reordered from lowest to highest voltage:
| Battery Shape | Chemistry | Nominal Voltage | Rechargeable? |
|---|---|---|---|
| AA, AAA, C, D (Rechargeable) | NiMH or NiCd | 1.2V | Yes |
| AA, AAA, C, and D | Alkaline or Zinc-carbon | 1.5V | No |
| Coin Cell | Lithium | 3V | No |
| Silver Flat Pack | Lithium Polymer (LiPo) | 3.7V | Yes |
| 9V | Alkaline or Zinc-carbon | 9V | No |
| Car Battery | Six-cell lead acid | 12.6V | Yes |
Bibliography:
- youtu.be/HQ1lrEQsj4c?t=51 shows Fluke 731B Voltage Standard which contains 1.018 values due to Weston cell voltage standard
