I have a 2y old PF5NU1G (a second run Mechrevo CODE 01) as well, and the battery has decayed to ~73Wh (from a 91Wh original design). The one bright side is that the replacement battery, PFIDG-03-13-3S2P-0, seems to be pretty cheap ($60, shipped by boat from China) if you know you're going to stick to the same laptop for a while... https://www.aliexpress.com/i/3256803017144797.html