Voltage Drop Resistor (?) on a Wall Wort?

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I could use a little help adding a power supply to a freshly installed Ring Video Doorbell 2. Right now it’s running on the supplied rechargeable battery and ‘ding dongs’ via a shared Chime Pro. There is no AC powered doorbell at this entry and I’d like to be able to maximize it’s performance without depleting the battery weekly.

At issue: A lot of conflicting data on the use of wall warts.

a) Ring Help: https://support.ring.com/hc/en-us/articles/205180710-How-to-Connect-Your-Ring-Video-Doorbell-Directly-to-a-Low-Voltage-Transformer-Without-a-Pre-existing-Doorbell (applies to both Ring Video and Ring Video Doorbell 2) states that you must splice in a 25 ohm / 50 watt series resistor.

I can only think that the resistor in series with the Ring is to produce a voltage drop. If the Ring is also 25 ohms, the net of a 24V supply would be 12V to each. Is that closer to what we want?? Why start with a 24V transformer if we really want far less?

b) Ring Sales: https://shop.ring.com/collections/accessories/products/plug-in-adapter for For Ring Video Doorbell, Video Doorbell 2 and Video Doorbell Pro. Tech specs: 24V @ 20VA (so almost an amp). Installation instructions? Just connect it to your product! No mention of a resistor needed or critical doorbell settings. Conflicts with “a”.

c) I see transformer listings on Amazon ranging from 16V/500mA all the way to 24V with a few amps – and each has hundreds of positive reviews stating they all work great. Ring’s instructions say the doorbell 2 works with 8 to 24V. Given that this is basically for charge maintenance and not primary power (and I assume we must have DC rectification and a good 6V max regulator in play to feed a Lithium battery, how much AC output do we really need??

On a lark (returnable to Amazon) I bought a Voyaux Power Supply Adapter. The box is plastered with Ring Doorbell product pictures and assurances that it works with them. It is spec’ed at 16V AC / 800mA. Can I get away with a smaller resistor, or no resistor? Are we closer to the doorbell’s needs?

d) Despite dire warnings not to use with DC power systems, I see there are various solar power kits available. Last I checked, photovoltaic cells had a DC output. I’m left confused….

Thanks!!

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Yes, I noticed that I spelled “Wart” inconsistently in my post. What do you want from an engineer? :wink:

I’m a little disappointed that nobody has looked into this. On to my next thought…

Attempting to measure input impediance on the power screws of the Video Doorbell 2 didn’t get me any useful data, so attempting to figure out an actual voltage desired failed.

So… There are plenty of 120V AC to 9V AC warts available on Amazon. Why start with 24V or even 16V if the goal is to deliver less?

I just have this technical objection to applying higher voltage and splicing in a toaster element just to obtain an end result of a lower applied voltage at the back of the Ring.