Owning a car in a cold climate means knowing that silence on a frozen morning is the most expensive sound there is. A standard battery might get you through a mild year, but a heavy-duty one is an investment in actually getting to work when the temperature drops. Early autumn is the sweet spot to buy because shops aren't yet swamped with people whose cars just died in the first frost.
While you can't usually negotiate the price of a battery like you would a whole car, you can control how you pay for it. Using a specific window of time to pay off the $220 cost means you aren't hit with a big bill right before the holidays. We can look at this as a small monthly maintenance fee rather than a one-time shock to your checking account.
The 0% intro APR for 15 months on purchases and balance transfers is a hard deadline. If you still have a balance when those fifteen months are up, the standard interest rate kicks in on whatever is left, which makes your maintenance much more expensive.