Method 1) You can use the product’s ‘Batteries’ feature field to include text about batteries. When used here, a special ‘batteries:’ bullet point will be shown in the Product Specifications block.
Method 2) You can include bullet point in the ‘Product Features’ block. When used here, the text will appear in the Product Features block. This method has the added benefit that you can use the CSV Import/Export Tools to update lots of items at once.
Method 3) You could add text within the Full Description. This method would allow you to set special coloring or other layout options if desired. When used here, the text will appear in the Full Description block on the front-end.