When the H8000 is running normally you don't always get a reaction from putting the card in. If you hit the PROGRAM key with a card in you should get a flash of the BUSY light as it checks for User progs.
There is no relationship between the card and the Lithium battery – you should only suspect the battery if you regularly get bad checksum messages on powerup.
It is not necessary to send the unit back home to change the battery – a dealer or technically competent person should be able to do this (if necessary – see above).
