Cell phone weirdness

[Hawkmoon]

I have a couple of cheap cell phones that I use for playing with new (to me) apps so I won't inadvertently mess up the phone I use and need on a regular basis. There's a compass / GPS app that I want to try in my car driving to work tomorrow, so I pulled out burner phone #2 and installed the app. When I took the phone out of the box, it showed the battery status as 97%.

Not wanting to run it down while installing the app, I connected it to a charger and plugged it in, then installed the app and played with the configuration for a couple of minutes. Battery charge state was now down to 91%.

So I turned off the phone and left it for a while. Came back and it was at 86%. I was using a generic charging adapter from Amazon, so I switched to the one that came with the phone and tried again. Went down to 81%. So I ditched the adapters altogether and plugged the USB cord directly into my computer. Went down to 77%.

What's going on?

[RocketMan]

Defective battery or the phone's internal charging circuitry is borked.

[Hawkmoon]

I think it's a flaky charging socket in the cheap Chinese (ZTE) phone.

I tried a third power cord, and another power adapter, and it charged right up. My clue was when I had cord #2 plugged into the computer. With the phone turned off and just sitting on my desk, the computer was constantly making the system chime sound for when a device is connected to or disconnected from the USB port.

[lee n. field]

The USB 3 B micro connectors that a lot of things use for power seem to wear out quickly.  "Does this cable work?  Does that one?"  And the charger port it plugs into could likewise have gotten buggered.

[Brad Johnson]

Cable was my first thought. Like Lee said, USB micro-B connectors are pretty fragile.

Brad

[MechAg94]

It can also be cords and power adapters that are bad or don't provide enough power/voltage to charge effectively.  I have had power adapters fail as well. 

https://www.amazon.com/dp/B0B3J6Z6SZ?psc=1&ref=ppx_yo2ov_dt_b_product_details
I got a new phone recently and got this set of chargers with 10 foot cords.  They work great.  Charges up my phone pretty fast.  I noticed my older charges don't do near as well (lower power/voltage?) and barely keep up with use playing a video.  Anyway, I need to get another pair of them maybe with 6 foot cords this time.  I am considering replacing all the random power adapters I have.