2nd gen video doorbell model 5UM5E5

Hi, I have a 2nd gen video doorbell and as I have to keep taking it off to charge (every 2 weeks) I thought I'd get a transformer (non ring from Amazon) I have had 2 and both failed after working for a while. The health status changed from battery to hardwired, then when they failed back to battery. I then purchased the ring transformer which I connected yesterday. I check voltage first and it showed 24 volts before connecting it to the doorbell. Once connected it hasn't changed from battery to hardwired in the health on the app. since yesterday is has gone from 85% to 80% approx 24 hours? I removed the wiring and checked again with wires disconnected from the doorbell and again shows 24volts. When connected it shows much lower voltage which I suspect is trickle charge? My questions are 1/ Should health status not show as hardwired? 2/ Why is the charged % dropping? Many thanks in advance for any help / advice.