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Nest Protect 2nd gen POE

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Hey all i am looking for some advice in how to go about my project with a Nest Protect gen 2.

In my home i have ran cat6 wire to all 3 locations that require a smoke detector. These cat6 cables are connected to a POE switch for powering the Nest Protect.

The version i picked up for the Nest Protect is the battery version. I am wanting to convert the battery to the POE in order to power it by POE instead of battery. The Nest Protect uses 6 x AA batteries that equal ~9vdc total.

I am converting the POE to 9vdc via a converter:

However my question is- do I need to wire up the 6 battery placers in parallel or series? It would seem that the Nest Protect AC version has only 3 x AA for power backup. Not sure if that matters in my case or not.

I would like to keep a battery backup just in case the POE goes out for whatever reason. The POE has a battery backup as well.


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I'm confused. Why do think you have need 6 battery placers when one of them already puts on 9V? Or do you have 6 Nest devices?

Check the battery connections in the Nest device. Are all 6 batteries wired in series? Or is it two groups of 3 batteries in series that are wired in parallel? You should more or less be able to tell by looking at the contacts in the battery holder.
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Looking at the picture, it's not clear the batteries are in series. All the positive ends are pointing towards the center.


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It looks like there is a USB connector under the battery door at the top edge of your picture. Can it be powered through that USB plug instead of batteries?

If so, that means 5Volts, and you don't need to mess with battery substitutes. Just wire a USB cable to the 5 Volt output of your POE converter.


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I think you have the ersatz POE? The one that isn't compliant with the 802.3at or 802.3af standard.

They may use pair 1 and pair 2 for data and pair 3 and pair for for power. It won't do the signature test etc. So, you get 10/100 Ethernet.


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it says power + data on the lan jack, doesnt that imply that it is POE ready? batteries are prolly just for backup power?


New Member
I think you're referring to the PoE adaptor that is clearely NOT part of the Nest packaging, it's just a classic PoE splitter (your switch sends Data+power on the cable and those boxes can split them and isolate the power)
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