@Wayne-TP 

I have installed my KE100s end of October. 

An update
I was sent a debug firmware to my KH100 hub which I downloaded & installed
I then removed the batteries from each of the units that showed the incorrect battery
status.
I re installed the same batteries.
The 2 units are now showing the correct battery status on the Kasa app on my smartphone..
HTH

I'm also getting this fault. Tried new and tested batteries.

Is it just a case of disconnecting them and reconnecting them several times?

Have tried 3 times so far....

  @Necessiter 

No changing the batterries did not work for me either.
I was sent an email by TP-Link support who had read my message on here.

They sent me a debug firmware to my KH100 hub which I downloaded & installed.

Everything regarding the battery indicators worked fine after I did that.

And continues to work fine I might add

  @Wayne-TP 

Any chance that I can get help too?

The solution I found that worked for 2 different devices:

Once you get the low battery thing, it's convinced it's low battery even if you change them.

Remove the device from your app.

Disconnect it from the radiator and pop up the batteries, re-install and reset the device.

While still disconnected from the radiator, add back into the app.

It might fail the firmware update, it might not (one of mine did, the other didn't).

Check it and you should get the E1 error - i.e. it's not connected to the radiator.

Connect it, and all will be fine.

If you need to update the firmware, go to "me" on the bottom menu and do the firmware update thing.

Hope this helps, and I hope Kasa update the software to fix this issue - it's not the batteries.

  @Necessiter what is your firmware version? M