I installed my battery 2k doorbell last week, using my existing doorbell wiring, and tested it all very carefully before I connected it up because I wasn’t sure whether to use my old house chime unit. There’s a setting that you MUST change if you bypass the mechanical chime. It’s in doorbell settings, “Indoor Chime”, “Existing doorbell chime”. If indoor chime is set to “on” then when the bell-push is pressed it will close the contact for the ac supply, which will short-circuit the transformer if the chime itself isn’t in the circuit. This is NOT GOOD and likely to cause damage longer term.
My Friedland 14v ac transformer passes 0.5amps when the house chime unit rings (which is fine) and 0.02 amps when it isn’t ringing (the battery is still fully charged, so that’s about what I expected) but if the chime is bypassed and the setting hasn’t been changed to “off” then when the bell-push is pressed the current jumps to over 1.5 amps - which is nearly 80 times what it should be, and well above my transformer’s maximum specified output. Most transformers have protection against overload like this, but it’s still likely to cause damage if it happens frequently. If the ‘indoor chime’ setting is set to off then the doorbell doesn’t try to ring the chime, and doesn’t short-circuit the transformer.
Eufy’s complete lack of a decent manual (which should include this warning) make me wonder where Eufy’s priorities lie. The doorbell is an excellent product but the user documentation is virtually non-existent.
Incidentally, the idea of connecting a 5v dc supply to the terminals on the doorbell is totally wrong - the voltage specification is 8-24v AC. [as I’ve just seen pointed out in the post above]