26R is group and size for that Batt. Yes, you might have a small draw on the battery when not in use. Could be in the alt. A bad diode. Use a test light to check for a draw. Take the clip, hook it to the positive battery cable, removed from the battery, and take the pointed probe to the positive post on batt. It should not light at all. If it does, there is a draw. The brighter the light the more drain.