@Jamval I contacted Tapo support chat today.  I asked for an explanation of the 2 random notifications I've been receiving.  Are they normal or do they indicate a problem?  The user guide makes no mention of what those notifications mean.  Instead of anwering my question, the chat support person asked me to go outside, disconnect the hardwiring to the D225, do a factory reset, and start over again.  Support never answered my question as to what the random powering notification messages mean?  Why would I have to do a complete reset to get an explanation of what those messages mean? The chat support person got impatient with me when I was typing a response, are they going to hold a chat session open while I'm outside, disconnecting the D225 from the hardwiring, doing a factory reset and starting from scratch all over again?  Sounds like a tactic to get rid of me.  Also sounds like their notification messages generated by their app is not documented.

  @Jamval A TP-Link Tapo technician called me back.  He told me that when hardwired I should not be getting random messages that powering switches back and forth from  battery and hardwiring.  He told me that when hardwired the D225 always receives power from the hardwired transformer.  The only time it switches to battery power is during a power outage.  If power is out for an extended period where there are motion and recording events the battery level will go down.  When power comes back on, the battery will be trickle charged back to 100% while the D225 functions are powered by the hardwired transformer.  The Tapo technician asked me for my D225 MAC address so they could 'keep an eye on it.  (?)  I gave them the MAC address. For the next day the battery icon continued to display the green charging status and gradually came back up to 100% and then the battery icon turned grey and has stayed at 100% ever since.

I think what happened is when I originally set up my D225 I did not charge the battery up to 100% with the included USB cable.  It was around 96% when I hardwired it.  It never came up to 100% during the first 6 days while hard wired.  I don't know if Tapo support pushed a firmware fix to my D225 or it just took a week to finally trickle charge to 100%, but it seems to be working as described by the technician now.

I asked for a more technial explanation of how the D225 could run off a 5.0v DC battery and also off a 8-24v AC transformer?  The D225 must have be an internal AC to DC transformer.  The technician would not confirm or deny that, maybe for proprietary reasons.  My old Ring doorbell when hardwired did not work that way.  It was always powered by the battery even when hardwired which supplied a trickle charge to the battery.  On the Ring doorbell it was possible to run the battery down to 0% even when hard wired.

One disconcerting thing that I should have realized before buying the D225 is that the internal battery is not user replaceable.  

  @Jamval I have the D225 hardwired as well and I cannot keep it in "Always on Mode."  For some reason the internal battery runs down and goes into battery mode?  It then charges back up to 100% but never goes back to "Always on Mode."

Also, I cannot figure out how to have it record 24/7 even in "Always on Mode."  It just records snippets like in battery mode.  I really regret getting this thing.

  @delslow   I went with Tapo cameras because I have a TP-Link Deco Mesh 6 router system and assumed that would facilitate the setup, or at least remove one of the typical exuses that customer support people use "the problem is with your router". 

So far I like the D225.  The Tapo app is the problem.  It's not very intuitive, and the user manual is bordeline useless.  There's no documenttion as to the meaning of some of the cryptic notification message.  I got one message that said "Unusally fast 3% drop in battery level in 20 minutes, consider lowering motion detection sensitivity levels".  This is while it was hardwired.  

Before I got the D225 I bought an indoor C220 camera and a C120.  It seemed that I had to do every step of the intial setup twice before it was successful.  Even the initial pairing failed on the first try for both.  

Next came the D225.  Again, it took 2 tries to pair it.  From what I've read here and on other smart home forums, what ever mode chosen during the intial setup for 'Always on' (enableed or disabled) wouldn't switch over if you want to change it later.  Other users found that they had to do a factory reset and start from scratch chosing whether or not they wanted 'Always on' enbaled on the initial set up.  

I was confused by the 'always on' mode, but since I didn't intend to use it, I didn't try to get clarification. The stated advantage is that since it is always on when motion is detected the saved video file will start 4 seconds before the detection.  When always on is disabled, recording starts after motion is detected which may only get the back of a person as they walk away from the camera.  It sounds like 'always on' is constantly recording video but only saving files starting 4 seconds before a motion event is detected.

  @Jamval This is exactly my problem.  I had a Ring doorbell and replaced it with the D225.  My old doorbell wiring powered the Ring just fine.  I've had nothing but irritation with the d225.  The device constantly switches from battery to hardwire.  I've removed the d225, confirmed the wiring was solid, switched the wire polarity, checked that there was adequate power with a tester, bypassed the chime and it still switches, like 50 times a day.  I've been in contact with technical support and was told the problem was being escalated, but they've gone radio silent for days.  I think my only alternative is to return the device.   Other than the really irritating hardware problem, the device is fine.

  @kpwk80a Mine gives me a notification when it 'switches from battery powered' to 'hardwire powered' and vice versa.  But, this only happens a few times a month.  I think these notifications are misleading. It seems to me that the D225 functions essentially the same as my old Ring Doorbell did.  Even though they are hardwired, they still are powered by the battery.  In fact the Ring instructions say that the battery must be installed even when hard wired.  The hardwiring only provides a trickle charge to keep the battery topped off to 100%. The hardwire is from a 16v AC  10VA output transformer.  Battery power is 5 v DC.  The device couldn't work off both 16v AC and 5v DC without some fairly complex switching circuit, so I'm convinced that all the hard wiring does is keep the battery charged.  On my Ring doorbell I would occasionally check the battery level on the Ring app and it wasn't always topped off at 100%. Depending on usage and weather (temperature can effect battery) the battery could drain faster than the trickle charge can keep up.  I believe the same technology is used in the Tapo D225.  I actually spoke to 2 different TP-link tech support guys and asked them about this. Initially mine was acting like yours, constant notifications of switching power sources.  The first tech said the D225 should not be giving me those switching notifications and he asked me to provide the MAC address of my device, but that was only after I told him that I was going to return the device.  After I gave them the MAC address I think they pushed a firmware update to my device, because after that the switching notifications only happens a few times a month.  The 2nd tech called me a few days later to ask how it was performing. (Unheard of - tech support called me back, wow, I was impressed).  He told me the power source switching notifications are not normal.  That doesn't make sense, if it's not normal, why would Tapo make those notifications available?  I asked him if in fact the D225 is always battery powered and the hard wiring only supplies a trickle charge to keep the battery topped off.  He was vague and really didn't answer my question.  I suspect the technology is proprietary.  

If I were in your situation, I would check what level the battery is at when you get the switching notifications.  For example my battery level drops down to about 96% before I get the switching to hard wire powering.  Then when I get the switching to battery power notification the battery level is 100%. It takes several hours for the trickle charge from the transformer to bring it back up from 96% to 100%.  Maybe yours is triggering the notifications at 99%?  Or if you are getting a lot of motion detection events that can drain the battery faster and cause the switching notifications. I adjusted my motion detection zones so It's not picking up every car that drives by my house.  I really think the power source switching notifications are misleading, I don't believe it's really switching back and forth from 5v DC battery power to 16v AC hard wire power.

  @Jamval I have exactly the same issue with the notification swtiched to battery powering, followed 20 seconds later by switched to hardwire powering Battery powering no longer supported. The difference is that it happens every time the bell is pressed. I have checked the wiring and voltages. The battery always reads 100%.

Curious if anyone else, or whether you resolved this. I am on the latest firmware. 

  @Jamval 

Check out my thread I just posted.  I have similar issues. I dont know what caused it, but my battery usage spiked yesterdfay while hardwired.  Now the unit is automatically turning off "Always-On" mode.

"Exited Always-On mode since battery drained too fast." My doorbell is hardwired?? - Smart Home Community

  @mjbarnard My doorbell hardly ever gets pressed so I don't know if pressing the doorbell on mine triggers the notifications. Do you have "Always On" mode enabled.  I don't use the 'Always On' mode.  I want my existing door chime to work when the doorbell is pressed.  If you have an existing door chime connected to the same transformer that is powering the Tapo D225 you need to bypass the existing door chime.  I suspect that "Always On" mode is taking enough power from the hardwired transformer that the existing door chime will cause problems if it is not bypassed.

  @HunterK916 I never used "Always On" mode.  I want my old doorbell chime to work if my Tapo doorbell is depressed.  The way I understand the system is that "Always On" mode takes all the available power from the hardwired transformer to the point that the existing door chime must be bypassed if you elect to use "Always On" mode.  If you have an existing door chime wired to the transformer being used to power the Tapo D225 it needs to be bypassed, there's instructions on how to do that that came with the Tapo D225.