With my ///M roadster it took 3 visits to the dealer before they relented and changed the battery.

However in my case it was pretty obvious, the car wouldn't hold onto a charge for more than two days and was towed to the dealer on multiple occasions...

The first time they "tested" the voltage and found that the iPod kit was drawing power when the car was off.

The second time, the power draw was normal and the car was holding a charge fine — so they claim.

The third time (perhaps due to my anger) and the fact that the car was dead again, they really didn't have much of a choice.

So, my point is, they won't replace it outright. & their test is pretty rudimentary (i.e. charge up the battery, see if it retains a charge right away). Insist they hold onto the vehicle overnight or for two days and periodically test the battery level. Keep going in and they will have to give in.

btw, ///M roadster has been perfect ever since I got the battery swapped