Most Chevrolet Equinoxes, including the 2013 model, have the battery under the hood and behind the driver’s side headlight. They’re hard to locate at first because the battery is underneath some other vehicle components. You usually have to remove other parts to expose the battery to access it.
Most vehicle batteries last between three to five years before they need to be replaced. If your Equinox’s battery is approaching this age, it won’t hurt to have a mechanic look it over and help you decide if you should go ahead and replace it.