Is my Microsoft Universal Mobile Keyboard battery dead?

[Goi]

Hi guys,

I inherited a MS UMK Bluetooth keyboard, and charged it overnight. I then unplugged it and tried to pair it, but my Android phone couldn't detect it. I plugged the USB cable and tried again, and it was able to pair this time, and I was able to use it. However, once I unplugged the cable, it stops working.

I've googled around and didn't get anything useful. Some say the charger may not be compatible, but if so, why would it work while plugged in?

What else could I try before concluding that the battery isn't able to hold a charge anymore?

BTW the unit looks brand new so it doesn't look like it was used much at all.

 

[mindless1]

Does it have any indicators like LED color change when it's supposed to have fully charged?

Ultimately the definitive answer is pop it open, measure the battery voltage when it's supposed to be charging, what the charge termination voltage is (should be about 4.2V but not over that), and how much the voltage drops under load (powered on) and how long the charge lasts.

While you have it open, the battery may have markings on it that help find a replacement if needed, not necessarily needing to be something sold as specifically for that product, though if the original has the protection circuit on it then you need one with the protection circuit on it too, or transfer the old circuit board to the new battery and make sure if there is thermal detection, that it's in contact to work properly.

As far as a compatible charger, you didn't come right out and state it but I assume you are using an aftermarket /3rd party USB power brick? You could also measure the voltage drop while it's powering the keyboard, though I'd think it ought to be able to work and charge simultaneously if it's at least a 500mA @ 5V capable USB charger which practically anything in good working order has been for several years... but otherwise, sure try a different charger.

 

[Goi]

I think I remember seeing it blinking while charging overnight but I can't be sure. Now, when I plug in the USB cable, I see it light up (not blinking) for a few seconds before turning off. I guess it's fully charged then?

I'm using either a Ugreen or Baseus USB-PD charger. I'm trying it with the default power cable now connected to my desktop PC's USB ports and it's exhibiting the same behaviour.