Capacitor voltage problem

Form reading many of your posts I know that many are opposed to caps but I am a fan. I have dual batteries and alternators in my truck but I still want caps. I have two digital caps tied togeather one of them maintains appropriate voltage but the other will drain completely itself every couple of minutes and then recharge. I have checked the posts, solder connections on the ring terminals, voltage in, and grounding and everything looks fine. Am I not seeing something or is one of my caps dead!