The SCMS22H255PRBB0 is a 2.5 F supercapacitor from the KYOCERA AVX SCM series, rated at 6 V with an ESR of 180 mOhm at 1 kHz. This combination of capacitance and ESR defines the usable energy for a short-duration hold-up or backup application — the RC time constant (2.5 F × 180 mOhm) is about 0.45 seconds, so the part delivers its stored charge quickly, not as a slow-drain battery substitute. The 0%, +100% tolerance on capacitance means the actual part could measure anywhere from 2.5 F up to 5.0 F fresh from the reel. For a circuit that needs a minimum hold-up time, design around the 2.5 F floor; the extra headroom is a safety margin you cannot count on across temperature and ageing.
Through-hole radial can — board-fit and thermal reality
The body measures 0.787" × 0.394" (20.00 mm × 10.00 mm) — allow clearance for the vent and for the leads to pass through plated through-holes without shorting to adjacent traces. Lifetime is rated at 1000 hours at 65°C. Every 10°C below that roughly doubles the expected life per the Arrhenius model common to electrolytic and supercapacitor cans — at 45°C you can expect several thousand hours.
The SCMS22H255PRBB0 is listed as Active by KYOCERA AVX.