Do you have a part number for that 1810mAh battery?Sure, I've fixed many cell phones, and media players (and of course, a million iPods back in the day).
The Onkyo/Pioneer are easy to service.
As far as battery life, replacing a battery that hardly holds a charge (or has overcharged and who's packaging is now all bloated), gives you that "brand new" playback time, like the phone/player used to have when you first got it.
....AND, you can even install a larger battery (like a 1810mah) for better than new playback time, but you need skillz to crimp or solder on a different connector to the battery pack.
Remember to recycle your old battery pack - DO NOT THROW IT IN THE REGULAR TRASH!
The original stock battery is available in Japan but not in the US.