i just used a single AA battery to see if a fuel gauge would move. gauge in my car was working, then it stopped, i had 4.95V from the VR on my instrument panel so i assumed my gauge was bad. swapped it out for another. still no workey.

so, i used a single AA batter wired to the gauge (not installed in any instrument cluster or anything, just two posts) and it went to about 1/4, the battery measured about 1.5V so two AA in series seems ok too..

remember, there is a VR on the instrument cluster, so the most the gauge should ever see is ~5V.