i dont know......but i dont think it will.cause ive taken my battery out before, put it back in and all it did was a beep. then there was an egg on the screen then i downloaded. i dont think its any different with a new battery
You have over a month to put in a new battery for you tama! And when you put in the new battery an egg should appear then you should hit B press download and you'll have the same character and same Gotchi-Points as you had before. But you will have to change the time and date because it will be at the same time and date when your tamagotchi ran out of batteries!