Anker/Eufy support got back to me, and said that they recommend the 24v 40va transformer here:
But… they didnt answer the question about needing a resistor 25ohm 50watt resistor or not (like Ring highly recommends to avoid fires). In addition, I was told that the wired option charges very “slow”, but clearly the unit doesnt have enough power if it continually drains the battery down to zero.
Really important: Here’s a warning about this specific transformer, or any that provide 24v 40va of output. The amperage will be 1.67amps. In order to avoid fires, you must use at least 20 AWG electric wire (or larger). 20 AWG will support 3 amps. While you can technically go for 22 AWG, which will support 1.8 amps, given these transformers are not regulated, expect some flux and/or spikes in the power delivered. In fact, to play it safe, go with 18 AWG that will support 10 amps if you are running this through your walls, so you only have to do it once.
I will update this thread when new info about the resistor if becomes available. If this saves you some time down the road, leave a note below!
Update: (7/8/2020) - Support got back to me and stated that they recommend a 25ohm 50watt resistor with the 24v 40va transformer for standalone powering of the doorbell. (e.g. if you either do not plan on using pre-existing wiring, or do not have a mechanical doorbell chime).
Resistor recommended by support:
But I suggest using the Ring wirewound resistor as it comes nicely shrinkwrapped and ready to be connected.
It says for use with ring devices only, but its the same resistor type – a resistor is a resistor.
Update: (8/28/2020) - Support has no idea what it is, so i alleged it could possibly be bad hardware.
But given the other posts on other forum posts (and also Mike’s post below) complaining about poor battery management and performance out of their battery doorbell, i doubt it. This just reeks of either a battery management or software/programming issue.
Anyhow, support did send me a RMA for the battery door bell. So I’ll try installing it and returning the old battery doorbell if there’s any improvements. But honestly this feels like Eufy just created a product and decided to screw over their customer base. Whether this was inadvertent, who knows… but it doesnt speak well towards the support of their products.
They seemed to have over promised and under delivered with many of their products.
The biggest gripe with the battery doorbell is the ability to not run this in any fashion but in optimal battery life while maintaining an adequate charge. (here’s the post where i talk about this). If you plan on using any of the advertised features of the doorbell beyond the basic “push to ring” functionality, right now you’ll be rather disappointed.
They also seemed to have under delivered with their homebase 2 stuff as well – with expandable storage, or RTSP support for their doorbells – but thats a different topic.