While the low battery voltage might be a contributing factor, it is most likely that your 5 volt board is dead. Death came slowly to my, first sound cut in and out then it just stopped responding. In my case the battery was fully charged, but it didn’t matter. Yours should have done something with a 9 volt.
The 5 volt board, generally, cannot be repaired. You will need to replace it with PS3. If you can find a kit you could do it yourself or contact a tech, like Alan, and get a cost for replacement.
