Well for starters if it's a Cooper S 2002-2006, you'll need to be looking in the boot- er, TRUNK for it. There was not enough room for it under the hood. After 2006 I don't know.
You can change the battery in your Mini Cooper by releasing the hood lock located on the bottom portion of the dashboard. The key to unlock the battery cover should be on the side of the battery cover.
I will assume you mean "Does a Mini Cooper have a battery?" Yes, they do.
No
2005 Mini Cooper replace car battery. Alternative to MINI part
To change the battery in the Mini Cooper keyless remote, it is necessary to first open the device. This can be done by removing the key chain and gently prying the seam at the opening end apart. Now the battery is accessible for easy replacement.
How to change a radiator in a 2008 mini cooper
$166.45 at Mini Cooper Dealership, but you can buy it at Western Auto for $145.99.
were do I put stickers on headlamps to change to Europe on a mini cooper
Describe in detail how to change the oil in a 2005 mini cooper.
Batteries Plus
Use your key in the door.
Purchase a simple battery charger like a Battery Tender, or a Ctek. Follow instructions.