A few adages spring to mind:
- Never a lender nor a borrower be.
- There are two things a man should never lend out: his woman, and his car.
I, like someone else mentioned, am a firm believer in bringing something back better than when you borrowed it. It used to be etiquette (waaay back in the day) to return someone's car with a full tank of fuel after borrowing it.
Like the OP, I'm not the type to go asking someone for money - if they don't feel compelled by their morals/conscience to help pay for the battery, then I don't want their money anyways. I guess I'm proud like that.
So don't borrow him anything again. And if you're lending something to someone again, be sure to stipulate the boundaries or rules. they might think you're full of shit, but at the end of the day, it's your things.