Is there a backup battery that needs replacing?

There isn't a separate PRAM battery in Unibody MacBook Pros, although the pre-Unibody generations (A1226 and A1260) had them.

MacBook Pro 15" Core 2 Duo Models A1226 and A1260 PRAM Battery Replacement

If your battery runs down and it's not plugged into the charger, you should expect to lose all that PRAM-specific information: Clock/calendar/time zone, default network settings, and possibly default display sync. It's worth considering that your battery may be pretty old (A1286 runs from 2008 to 2013), so you might want to think about replacing it - either with an Apple-branded version, or with a new OEM replacement from eBay/online resellers.

Remember that different generations of A1286 have different, incompatible batteries, and different replacement procedures. Apple still stocked replacements for the late 2008/early 2009 generation battery last year.

MacBook Pro 15" Unibody (Late 2008-Early 2009) Battery

MacBook Pro 15" Unibody Late 2008 and Early 2009 Battery Replacement

MacBook Pro 15" Unibody (Mid 2009-Mid 2010) Battery

MacBook Pro 15" Unibody 2.53 GHz Mid 2009 Battery Replacement

MacBook Pro 15" Unibody Mid 2010 Battery Replacement

[produto vinculado ausente ou desativado: IF161-081]

MacBook Pro 15" Unibody Early 2011 Battery Replacement

MacBook Pro 15" Unibody Late 2011 Battery Replacement

MacBook Pro 15" Unibody Mid 2012 Battery Replacement