[en] We have built a new small electrostatic ion storage ring, the so-called mini-ring, in order to store ion beams for long durations (up to seconds) using a limited number of electrodes in limited space. In this paper, we demonstrate the capability of the mini-ring to store ions on a rather long time scale (100 ms) limited by collisions on the background gas. We also show that by measuring the frequency of ion motion around the ring, we can use the mini-ring as an energy analyzer to determine the energy loss of F^- anions produced in the double electron transfer process in 4 keV F⁺-Ar collisions.