First, make the deposit a function of battery size not item size or cost (small battery $5 deposit, medium battery $10, large $50). This way the environmental cost of a specific battery is linked to the consumer's cost in a way that it isn't really now when the variation in battery cost is swallowed up in the cost of the item itself.
Second, peg this deposit to inflation. 20 years ago the 5c deposit on a beer can meant a lot more than it does today. I'm old enough to remember my fairly well off grandparents saving up their cans and returning them. Today, nobody I know bothers.