Me too. My Priv battery was only good for a few hours. There are a few YouTube videos on how to change the battery, just Google “Blackberry Priv Battery replacement” and you can get a 3rd party battery on Amazon for around $50. An original is about $150 and up.
You need to power down and remove the SIM and memory cards before trying to open the case.
It can be a bit tricky opening the case, that was my only problem. It feels like you will break it by pulling too hard, but it won’t break. I had to review the videos a few times to feel confident pulling the case apart.
You need a special screwdriver for 2 screws holding the connector down.
You also have to be very careful and very slow to pull the old battery off the glue holding it down. You don’t need glue to reassemble.
Reassembly takes a very few minutes. Just make sure the power and audio buttons are well in place first and that the cover clicks into place all around. Replace the SIM and memory cards then power up and recharge and you’re done.