nest doorbell battery will not hold a charge while wired

[dg1sek]

Like others have already reported here in 2021 and 2022, I have installed a nest doorbell with battery, wired to a 24V transformer. Transformer is massively overdimensionned. Doorbell is an old analog ringer (coil with a moving hammer) that is in series to the nest. The cable between the two is about 25m long as the doorbell is on the street and there is about 15m of garden between the house and the street.

What I observe (and what is confirmed from the other posts) is that the doorbell is discharging itself in about 4 weeks, while it normally should be recharging from the leaky current that it can get through the wire, drawing as few power as it can without making the ringer ring. In my case as there are quite some people walking by the doorbell obviously there are lots of events per days. It seems that the design of the whole thing is pretty poor as apparently the recharging current it will pull from its the voltage divider formed by its own interior resistance and the ringer  is not sufficient to cover that much video. 

I feel that this is a design issue google nest R&D should address more clearly. The device is basically not usable in the advertised use case if you have too many events, and even less so when the charging current it can get from the voltage division is not high enough. I am wondering if it could be solved by using a different ringer, or by introducing an additional resistance in the circuit, but I somehow feel that this is a hardware design issue google needs to address.

Besides that, a 2nd inconvenience: when I bought the doorbell, I also bought the home hub max so that we could easily see who is ringing on the door on the screen. Well... that use case seems to be so extravagant (ouch) that it is not foreseen.

Guys... I am deeply disappointed by this solution. I was expecting more from google. I thought you are able to hire the best engineers... being myself electrical engineer and working in the domains for >30 years I am puzzled that supposedly good engineers can bring products to market with so many issues. 

[Ashepherdson]

Have you tested what the actual output of the wires where your doorbell is hooked up is?  Sometimes is the run of wire that is the issue.  I've had mine hooked up since it's initial release with no power issues whatsoever, and I get a ton of notifications as I'm in a small townhome community with a lot of traffic. 

[EmptyNester]

Hello,  I also have a bit of an engineer back ground and share with you the design issues (Failures) with these products.   

One thing that comes to mind is how old is your camera?  The problem might be the internal battery (not user replaceable by the way) may have reach its end of life and is just fully charging.   Reading thru this forum it seems like the life of these battery cams is about 3-5 years but that is just a guess.

As for the trickle charge I believe the purpose of the 'PUCK' that we all install in the mechanical chime is what stop the chime from trying to ring while the battery is 'trickle' charging from the transformer. 

This may not me much help but if you get to the bottom of this I'd love to hear it.

Good luck

[dg1sek]

Thanks. The camera is new, it never really worked well from the start.

Yes I measured voltage without the doorbell connected…. 24V… on a (low impendance) voltmeter.
 

My assumption is that they probably implement a simple voltage divider between the bell, the cable and the doorbell that are all in series. The 20m (relatively thin) cable impedance is too high versus the too small impedance of the doorbell charging circuit using probably a resistor in serial in the doorbell loop to generate charging power. Of course they would not tell you in the tech spec how big that resistor would be.  Maybe I could modify it. As they are not really documenting how it works, difficult to be sure. And unfortunately I think easier to buy another manufacturers product than to swap my long cable, which would mean civil works... 
I'm really frustrated with the device. If ever anybody knowledgable from google engineering reads these forums and could explain the design of their charging circuit, it would really help to at least decide if it's worth putting time into fixing it or if it's a lost battle.

[EmptyNester]

I'm pretty tecky so I"m following what you are saying.   My gut tells me the adding a resister is not the way to go.

One thing to also check on your transformer is the VA (amps) rating.  This is the chart for the transformer specs.  Do you know what the VA rating is on your transformer?

Voltage and power requirements for Nest doorbells

	Nest Doorbell (battery)	Nest Doorbell (wired, 2nd gen)
Voltage	8 to 24 V AC	16 to 24 V AC (North America)
Power	10 to 40 VA	10 to 40 VA (North America)
Frequency	50 to 60 Hz	50 to 60 Hz

[dg1sek]

Yes, sure. I am using a  24V 30W transformer.

[EmptyNester]

Wow,, I'm out of ideas.  If it is less than a year old there is a good chance google will replace it.   To start that process you have to open an official support ticket and speak with an actual Google Person.  Here is the link to get you started:

https://support.google.com/googlenest/gethelp

[dg1sek]

Thanks for your efforts. I don't think replacing it with a new one will solve anything, unfortunately this whole thing smells like a poor design. If somebody from google engineering reads this, I'm happy to have a chat with them to help, but honestly it quite clearly all looks likey they"re not actively working on getting this solution to work better at all. Probably it all drowned in the nest/google acquistion waves...