Late to the party, but if the battery is rectangular, it's supposed to fit flush against the table. If it's bulging (sitting unevenly), then that's the problem... You might want to take it to a hazardous waste facility since it's pretty volatile and in the worst case scenario, might explode (and they pack a pretty decent wallop).
Granted, this is on purpose, but there's this... Also keep in mind the average laptop battery tends to be bigger too: