I read many (not all) of the replies that you've received about your battery quandry. Amoung the miriad of replies (both regarding batteries and coffee pots), I did not see any mention of a charger. With a one position charger, both batteries must have the same amp hours or RC. If you have a two position charger, they can be put on seperate circuits and amp hours do not matter. If it's a one circuit, the charger will, on automatic, continue charging the larger battery after the smaller one is charged. The result will be the frying of the smaller battery.
Good Luck,
George