My 2006 Ultra Classic just started charging then discharging. I noticed it when the discharge and engine light came on. The volt meter showed about 11 volts. A little while later the volt meter climbed to about 15 volts, and the lights went off. After a short distance the volt meter dropped and when it got below 12 the lights would come on again. This went on for about an hour and a half while I rode home. Does anyone know what the problem is? Thanks for any advise.