I think it’s more than 2 years, because some said 3 years is the battery warranty. but that claim needs to be verified.
The batteries can be replaced even after the warranty, I’ll just drum up the price of $300, I’m not sure exactly how much it costs to change the battery. With phonak, I must say that they don’t change the batteries, they replace the entire hearing aid with a new one. I think they figured it was cheaper for them to manufacture a new one than spend more hours repairing or replacing the battery. The battery is normally soldered to the motherboard and unfortunately it is very difficult to change without breaking something.
If a simpler battery change is an important characteristic, before buying new hearing aids, let the focus be on the manufacturer that enables this.