You're being a dbag for wanting to go back on ur word.
Seller is a dbag for sending u junk.
However, the seller is smart for not issuing you a refund. This way you are basically forced to ship him the dead battery or he can file a claim saying he sent you payment that you never honored via tracking.
Seller smarts > your smarts
I think you should just send the battery back (to cover yourself from paypal) and mark him as a bad buyer. You should not have ever told him you would ship it back if he refunded. You should have just gone through paypal in the first place.
I bought a battery that arrived as 'not described'... I notified the seller, he said he would refund me half. I said No and opened a claim.
Paypal decided in my favor in only 2 days..... just with me providing pics and Messages.
Paypal then refunded me FULL AMOUNT and asked me to ship it back, I called paypal the same day and talked to a very nice lady and explained to her that shipping a damaged battery in this condition would be hazordous to any shipping company.
She then overwrited the ship back policy and I got all my money back and now I have a Busted khc2400 that I have to take to a disposing facility.
Everyone says paypal are scammers, but if you do everything right and follow the claim rules, they are actually very helpful. They have saved my ass 2 times in my life and it didn't cost me anything