hrm that is weird. Seems like it should be charging it more than that. You might double check your settings and see if you have it set that it only charges 50% capacity or maybe check the battery chemistry or any other settings you can think of (sorry I'm not too familiar with that charger). Like the other said a full charge should be 12.6v, but 12.4 to 12.6v is a pretty good range.

GL