Can I buy the battery separately and what is the cost of the battery?

Yes, you can buy an optional lithium ion battery backup for the InnoSpire Mini Compressor Nebulizer. This battery will power the compressor for up to 90 minutes before needing to be recharged. It takes around 6 hours to fully recharge the battery.  You can use either standard AC or DC power to recharge the battery. You can also power the InnoSpire Mini using a 12V DC car adapter, attesting to its portability. You can also power the InnoSpire Mini by plugging it into a 110V AC wall outlet. You can see the cost of the InnoSpire Mini Compressor Nebulizer Battery on this page.