Nick,
Try leaving the Cab 2 either out of the Base Charging unit or up side down in it, when the batteries are already fully charged. You are probably over charging your batteries repeatedly. Damaging the Battery life.
My Legacy is on it's way back to Lionel, I just got the RA today. Going to invest in a used 993 Cab2 for a back up, so I can switch the Cab2's into different bases as needed.
PCRR/Dave