The Guppy input voltage range, for 2 x AAA batteries in series, is 2.2 to 3.6V. 2 x AAA batteries in series is achieved with the standard battery holder.

This implies:

  • 1.5V AAA batteries must be used.
  • 3.7V LTC batteries cannot be used.
  • 1.5V Lithium Iron Disulphide batteries are ideal. Examples of these are the Energizer Ultimate AAA. These have good temperature ranges and are reliable.
  • Alkaline batteries will work, but failure rates are higher, and the temperature range is lower. They will work down to 2.2V (1.1V per cell), which is near the low end of their capacity.