If the battery has died, so has the internal memory. The ESQ-1 came with a cartridge that included the original bank of sounds. If you do not have this cartridge, you can probably find a download by searching for ENSONIQ ESQ-1 Factory Sounds.
I did this and came up with several possibilities. Here are just two: http://www.syntaur.com/esq.html
I know if you get in touch with Syntaur they will have these sounds. http://www.buchty.net/ensoniq/
I don't know anything about this site, but it has some interesting things. Although I would be hesitant to try some of these "hacker tricks" as it could render instrument useless.