Join Date: May 2007
Location: St. Thomas Virgin Islands
I would not think that 20 minutes of idling would "drain your battery" and if you had a full charge on it overnight it should not run down in such a short time as you stated. Regarding the 13.5 volts vs 14.0 volts that could very easy be attributed to the accuracy of the volt meter. (I prefer a fluke meter) The fact that you are reading 13.5 volts probably indicates there is some current charging. Do several voltage checks, one with just the battery charged, engine not running. Depending on the volt meter accuracy it should be somewhere around 12.3 - 12.8. Now start the bike, for a second you will see the meter drop down on voltage as the starter pulls some current then it should rise, at idle it might show a little more then what the battery only was. As you rev the engine should see the voltage raise a little (under a volt) keep revving it higher and you will notice the voltage increasing to a point where the regulator steps in and does its work, at that point the voltage will flat top, not increase or decrease but saty level.
I think the exact voltage isn't as important as seeing these changes, which is about a volt from battery only, to bike revved up.
Another test would be to temporarily installing a car type amp meter between the negative battery post and ground and watch the charging current. A center reading amp meter is handy (shows neg or postive swing).
1997 VT 1100 ACE
1979 CX 500 Deluxe