To accomplish this, the best thing to keep in mind is that the counterman is a teacher to DIYers, and an assistant to the professional installer. The DIYer that comes to the counterman for information should be steered to just that, the information. Set up a display of literature and troubleshooting guides for this customer. A book, manual, video, or CD ROM can give the customer the information needed to begin doing some troubleshooting of their own. The counterman that helps the DIY customer help themselves is the trusted counterperson.
Information is half the battle, but everyone needs the right tools.
Other tools that can be merchandised right next to the batteries are those that help remove and install the battery or those that clean the battery terminals. The same holds true for other big ticket items such as alternators or starters. There are enough tools that are needed to keep an electrical system running smooth that will keep collateral sales high and the customers' repair jobs easier. Suggest using anti-corrosion spray treatments, paints, and cleaners. It will encourage the owner to keep a regular maintenance schedule for their car.