In all my years in the industry I have never seen any battery manufacturer volunteer to fix a battery under warranty. They have always wanted to charge for it until you plead your case. We had a customer who was spent the extra money for a battery that was warranteed for 7 years instead of the usual 5 years. The battery failed at five years and we asked the manufacturer why anyone would pay the extra money for the 7 year battery if it was only going to last for 5. After much discussion they agreed to give a better deal on a new replacement battery.
A battery warranty is like a dock leveler warranty. Unless you have the daily records of what the hour meter reading and specific gravity reading every time you charge the battery it gives the manufacturer an out. With dock levelers it is up ti you to prove that you have never driven over the leveler with an overloaded truck and you have never driven over it more tha X times per day.