Hello car enthusiasts, can someone clarify if BYD's lifetime free battery replacement for the first owner means the battery itself is free or just the labor cost?

Battery, warranty certificate is written like this.

The term "free battery replacement" isn't entirely accurate. If the after-sales service determines that it's natural degradation, they won't replace it. Only if there's a significant battery degradation or a malfunction will they replace it for free. Generally, the cost is fully covered, but the lifetime warranty comes with mileage requirements.