Mares Nemo Apneist problem

On my Apneist battery indicator started to flash and that means that I had to change battery, but I didn't.
Usually I turn comp. off after diving. I have about 70-80 dives with indicator flashing. One day while was on off it starts to beeb and give me all 8 on dislplay. When I try to power it on it start to count down 09,08,06,05 and turn off and on again. I somehow manage to turn it off. Next day it turns on and start ot beep and display was flashing. I didn't manage to turn it off. Then after some time it turns off by it self. Now I can not turn it on.
My question is: Is that normal "behaviour" when battery is dead? Did somebody experience same problem with Apneist.
Thank you.

Maybe someone will find this thread useful. After changing battery and o-ring everything is ok with computer. It was because battery was dead. Self powering, all eights on display, beeping, counting down, everything because of dead battery.

No. It is still under warranty so I didn't want to lose it.
I took it to authorized Mares servis. It is important to change o-ring aslo when replacing battery.