Is it safe to disconnect my battery?

My friend told me that I cannot disconnect the old battery completely on my Suzuki GSX1400 as this means I will “lose the memory in the ECU”. Is this correct?
Walter Calne, email
 
The moment you disconnect one of the battery leads it is disconnected “completely”, so if your friend’s theory was right no one would be able to change batteries. The only memory that is lost, is for the clock and trip meter which utilise a permanent live feed from the battery. The ECU will be fine.