@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.