@Wayne-TP 

Seems like a fairly common issue if people are making the effort to post about it here, there would likely be more people that are having the issue and not posting about it!

  @TKharde 

After messing around with my TD25 for over a week and calling TAPO support I figured it out by trial and error.

TAPO wanted pictures of my Door Chime so I sent them. Within an hour that emailed me back and indicated it would not work with my existing chime. I did not accept that answer.

I tried everything and I mean everything. I wanted it 'Wired' because I was not going to be charging this all the time.

I did not care if my existing chime 'Rang' I just wanted to use the power source,so..... I took the chime apart and cut and tied off the speaker wires. First problem solved.

Then I set it up 'Wired'. Make sure you charge you doorbell to 100%!

Went through the entire 'Wired' install and everything looked good, until I pressed the doorbell button! I was looking at the TAPO App the entire time of the install.

Once I pressed the doorbell button it worked but immediately switched to 'Battery' mode! OK I thought maybe my old door chime isn't compatible?

So what I started to do was turn options on and off and this took me a week to figure out.  Here is what solved my issue.

The Last option I tried was to shut off the 'Doorbell' from the TAPO App.

1. Make sure your battery is @ 100%.

2. If you cut and tie down your existing doorbell speaker wires you Do NOT NEED TO JUMPER the chime.

3. Install you TAPO doorbell as 'WIRED' finish the install and DON'T touch the doorbell!

4. Go the the App do the following.

    a. TURN OFF THE DOORBELL / DOORBELL RING this disables the chime on the unit itself for the outside. Every other option for the doorbell works.

    b.  GO to 'Power Options'  make sure power supply shows WIRED. At the bottom choose 'Working Mode' set it to 'Balanced'.

This completely solved my issues with the TAPO doorbell and it stays charged @ 100%. And it's wired using my OLD original chime.

I did not turn on "Always On' mode. I did test it and it works fine. I just don't think it's needed because all the other options you can setup that work much better.

My doorbell came with a WIFI chime so I just paired it with my TD25 and use that for inside the house.

Hope this helps someone!!

I am also having the same issue. 
Just today I got a notification saying the battery is draining. 

I installed the D235 in February and it been working fine until today.
I haven't changed anything from the initial installation. 

So it's strange that it started draining today? 

Any suggestions? 

I have recently purchased the Tapo D235 from Amazon in Australia, and the hardwired/Always on mode has also been giving me some grief.

Originally installed it with this transformer from Amazon:

24V 500mA Power Adapter,Extra Long 8m Extension Cabel Doorbell Transformer for Nest Ecobee Sensi, Honeywell,Ring Video Doorbell, Wyze Doorbell,Eufy Pro Cam,Zmodo WiFi Smart Door Bell Power Supply : Amazon.com.au: Home Improvement
 

After some additional research, I decided to replace it with a better 1A transformer last night:

24VAC 1A Unregulated Power Supply BareEnds | Jaycar Australia

Features:

• Suited to devices requiring 24VAC input

• 1.8m cable

• Unregulated

• Voltage Input: 240VAC, 50Hz

• Voltage Output: 24VAC

The doorbell was set to Always-On mode last night, with the battery slowly going down a few percent every few hours (hovering around the 60% to 65% battery range).

When I checked the app this morning, the percentage was slightly higher, though I noticed that Always-On mode had been turned off, and there was no notification of any sort to advise why.

Just purchased a new multimeter and measured 26.9V at the end of the cable connected to the doorbell.

How its wired - let me know if an issue:

Tapo D235 hard wired - Imgur

It is worth mentioning that I initially set the doorbell up as battery powered. I have just factory reset the doorbell in case a bug of some sort, and have set as wired from the get go. Will monitor the battery life and whether Always-On mode stays enabled or not. It's worth mentioning that we are on a busy road, so whilst notifications are limited to certain areas, the device may be processing a lot of events.

Firmware Up to Date

Version: 1.1.19 Build 250320 Rel.42136n

A few hours later, and I have received the notification:

Battery Draining Too Fast

"Doorbell": The battery has drained 5% in the past 4 hour(s).

It appears to have gone from 66% to 61% in 2-3 hours max, and has automatically turned off 'Always-On Mode'.

Should hardwiring the doorbell be sufficient to completely charge the Tapo D235 regardless of the features in use, or is it more comparable to a solar panel?

  @origamicrane Thanks, I emailed their Australian support and got an AI troubleshooting response back. Hopefully I'll hear back from them directly and receive a replacement if the issue. Heard a lot of good things about this doorbell on YouTube, so the experience so far has been a bit disappointing.

Just a quick update on this; TP-Link offered an RMA for the device, though I unplugged it, charged it to 100% (USB-C) and reconnected it to the newer 1A power supply and it has stayed at 100% charge ever since. Immediately connecting it to hard wiring at 80% charge was likely a mistake, its also possible the original 0.5A 8M long power supply wouldn't have provided enough power.

I'm still using this: 24VAC 1A Unregulated Power Supply BareEnds | Jaycar Australia

• Suited to devices requiring 24VAC input

• 1.8m cable

• Unregulated

• Voltage Input: 240VAC, 50Hz

• Voltage Output: 24VAC

Update 2: I switched back to the original wiring as it was easier for a neat install (being 8M long), and this has also since maintained 100% charge on a busy road.

24V 500mA Power Adapter,Extra Long 8m Extension Cabel Doorbell Transformer for Nest Ecobee Sensi, Honeywell,Ring Video Doorbell, Wyze Doorbell,Eufy Pro Cam,Zmodo WiFi Smart Door Bell Power Supply : Amazon.com.au: Home Improvement
 

tl;dr charge the doorbell to 100% first thing no matter what (prior to setup), as you will likely have less headaches with hardwiring.