Make motion sensors rechargable with small charging circuit?

So I have 10 Iris motion sensors, they operate using cr2 rechargable batteries. My question is if I can get some sort of small charging circuit that runs off a 5v micro USB port and just attach the positive and negative to the battery terminals inside the device (with rechargable lithium cells) so that the battery just acts as a backup for Power outages and I don't ever have to replace or charge anything? I was thinking if I soldered the charger to two small bits of metal and put them between the battery and terminals of the device it Should, in theory work right? Anyone try anything like this? Do they sell rechargable cr2 batteries with a built in charging circuit and usb port, like this but cr2
(It won't let me add links but theirs a battery with a micro USB port right in the side of it to charge it.)

Any help would be appreciated, thank you.

I think you would have to have all of the circuitry for the power be external to the device. You can't simultaneously charge a batter and power a device from the same leads. You can definitely wire in external power but the CR2 battery is 3v not 5v. You'd end up blowing up the rechargeable battery applying power to it constantly in the way you describe.

I was able to find the batteries you mention and the page doesn't say whether it provides power while it is charging, which obviously it would have to do. It only changes at 0.3A from USB though, so I suspect it can't. It says the typical use is in Flashlights.

I was unable to find a cr2 version, did I find one? Because I'm totally cool with external power of it functions. Anyone have experience with these batteries? Im really just trying to make a autonomous house, and battery replacement really makes it less autonomous. And if I have a battery device that can power any cheap motion sensor I can have autonomy, low cost and easy + cheap repair. I'm afraid if I buy a motion sensor with a rechargable battery it'll be hard to find an replacement battery, and be hard to change. I mean with an iPhone to swap the battery you have to scrape the damn thing off like a registration sticker. If you know an easy to deal with motion zigbee sensor with an easily replaceable battery I'm totally all ears :slight_smile:

My Iris sensors are going strong after 2 full years. I think this a solution in search of a problem thing.

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Well my Iris sensors probably will last some time, I don't think this is a problem or solution though. I'm simply trying to make something to remove maintenance requirements. I wouldn't call battery replacement a problem, but I would call it a task that would be easier to not have to do. I thought maybe you or someone else on the forums were aware of a rechargable zigbee motion sensor with an easy to replace battery so that it can function indefinitely without maintenance. I would actually prefer a motion sensor that functions via Ethernet with Poe support and a built in backup battery, but I'll take what I can get u know.

1 Like, on one had you have changing a battery once every 3-5 years. Something that takes about 5 mins. And on the other you have running cat5 cable to your sensor and not having it look like a mess. Which do you think would take more effort?

But also, what you really want is a wired alarm/sensor system with a battery backup. If you're going to run wires to all your sensors, why bother using Zigbee ones? Why not just uses wired sensors? You already have the wires run. It's much easier to battery backup one alarm panel than a bunch of sensors.


Likely in this case if the POE drops out, your ethernet isn't going to be working either in which case the battery back would be useless. If you are just looking to replace the batteries with external power, you can buy 3v power adapters that plug into the wall and just solder the wires to the battery tabs although I would definitely take the batteries out if you did this. Please DO NOT try charging a lithium battery without a proper charging circuit for it. That can easily cause an explosion and/or fire.

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I have three ups's just for power loss issues. I have a ups for my router and switch, ups for my hubs, and a bigger ups for my server. That's why I preferred Poe. Also if I could get wired sensors with network support I would definitely use them, do you know of any? I mean I came here hoping someone might be able to help. I'm sure it would take more effort to run Ethernet wires as well, but it's effort I put forth now and never have to deal with maintenance again. Dependability and reliability are what I'm looking for. I was thinking of just using an AC adapter and then just connect the AC adapters to ups units so they have backups but then the sensors would not individually have their own backup systems so they may loose power and disconnect, causing issues. Either from loose wires or if someone just Yanks the power. Plus if I don't want to run a bunch of power cables it means even more ups units.

Also it takes less than five minutes. Unless I'm not home. Bc if im in another state and something just stops working that becomes a problem. And takes much more than five minutes. And could result in burglary.

Only if you have only one motion sensor in your whole home. That's a complete disingenuous argument.
Also, your solution of running power to your wireless sensors makes no sense. If you are going to run wires to all your sensors, why go through the trouble of using wireless sensors. You have the wires, just use wired sensors. They are a hell of a lot cheaper and more reliable and faster to report. They could be wired into something like a Konnected board which can have a UPS. So, no backup necessary at each device. I don't understand why you would just run power to the devices but then still use something with a radio. The whole point is that they are WIRELESS. If you're going to make them wired sensors, then just be done with it and make them wired. Why try to cobble something together when there is already a solution? You're trying to DIY something that has a much better product that you can but off the shelf for much less money. It makes zero sense to me.

I have converted several battery sensors to mains power. I wrote the following article on the ST forum a few years ago:

I am in the process of converting a few of my v2 Iris sensors inspired by this article. Once complete I will compose an article with pictures on this community

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You have not answered my question. It makes no sense to me to use a wired, wireless sensor. If it's going to be wired, why not use a wired sensor?

Because power is nearby and me personally like Zigbee motion sensors.

Dude I'm here to find answers, all the answers and all the options so I can make an informed decision. So far I prefer the option of battery eliminators for existing sensors to make them last indefinitely with a ups. Also I have a good zigbee mesh going. Which wired ones are compatible with hubitat? And are they Poe wired or just wired to a hub of some sort? Are they easy to set up with hubitat?

Also if it makes no sense then you clearly haven't read anything I typed at all. I've listed a multitude of logical reasons.

  1. The sensors exist are easy to set up and can last indefinitely just like a wired sensor.
  2. They are easily available and use a common battery type
  3. the power source is separate from the device itself so if the device malfunctions I could just pop another one in for around $3 to $7 used
  4. the power source can reasonably convert any other CR2 based device into the equivalent of a wired device.
  5. If a sensor malfunctions due to the fact that it has a low battery and I'm unable to access that sensor because I'm not near it then whatever area that sensor is covering no longer has any security. That's not at all a disingenuous argument that's a legitimate concern. if for some reason both of my porch motion sensors batteries died and I go oh whatever and in reality someone just pulled the batteries out or something I would have no way of knowing unless I manually check the cameras. just because you're not that concerned with security doesn't mean that everyone else is as lax.
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None of that answers the question of why not used wired sensors instead of zigbee ones. They are cheaper and faster and more reliable. If you're going to run wires anyway, why not use wired sensors? You are going to spend more on the power supplies than you would on a new wired sensor.

Again, my wireless sensors already exist in my house. I already own them. and I'm not aware of any wired sensors compatible with habitat if you know of any feel free to share them instead of assuming that I know which ones work and which ones don't despite the fact that in the previous post I asked you to share them because I don't know. Maybe read the things I say before asking questions that are answered by prior posts. Or don't I mean me responding to this is just being nice.

Running wires back to the hub or to a single location is not practical. I have many motion sensors with external batteries or 115VAC outlet nearby which is easy and make sense to me. Also I want my sensors to have not just motion but temp and battery level report as well.

If they're wired, why do they need battery report?!?!

Why not :grin: