Charles Charger series 3000?

[mestrezat]

When I bought my boat back in 2007, it came with a Charles Charger 3000 to keep the start batteries fully charged when at a marina for long periods. I've never really used it as we are active cruisers and have to run the engine from time to time to get in and out of ports.
I finally turned it on and it hums nicely but when i check the voltage, it comes back at 12.7, the same was what the start batteries are. If I disconnect the wires from the charger and check them for output, it again comes back at either 12.7 or just over 24.7 volts when I touch different wires. Obviously the charger is designed for both 12 and 24 volt boats.
I don't know if it's actually putting out volts or it's smart enough to realize the batteries its supposed to be charging are already full and it's not supposed to put out any more. The meter on the top has never gone down to Zero, not has it gone about about 4. It seems stuck between 2 and 3. The manual I downloaded doesn't really say much about it other than how to wire it.
Any help would be appreciated. I'm in a place(South Africa) where I can get a new one if it's not putting out power.