Since it’s time for C8 owners to pivot from Iris v1 I’m looking to replace contact sensors.
Here’s what I’m looking for:
- Zigbee and C8 compatible
- CR2 battery
- reports temperature frequently
- bonus points for low price point.
Any recommendations?
The only Zigbee sensor that is still currently widely available that uses a CR2 battery is the Visonic MCT-370 (I can find them on eBay for pretty cheap; no idea if they have an official storefront or if they are even still made, but they are readily available in the US). Don't confuse these with siumilar models like the 340 that use coin cell batteries. Of course, if you can still find the Iris v2 sensors, they also use a CR2 and are many users' favorites--but many years past their discontinuation at this point, it seems unlikely.
I see some mixed reviews on the Visonic, claiming the battery only lasts a few months. I haven't had mine long enough to comment, but it's held up for a couple in my freezer so far (I'm only using it to measure temperature). Do you have a specific reason for preferring this battery size? Might I assume capacity? I once had this concern, but after looking at some specs, I stopped caring so much. A CR2450 usually has about 3/4 the capacity of a CR2, even though it looks a lot smaller, and you can find some sensors that take this size. The CentraLite Micro sensors are probably my favorite. (Specs I see for readily available CR2s claim about 800-1000 mAh, mostly on the lower end. Specs I'm seeing for CR2540s say about 610-630, most in the middle.)
A few others take a CR2032. While it doesn't look much smaller, the specs may again surprise you; ones I'm finding claim 220-230 mAh. The Sonoff SNB-04 is a Zigbee model I'm aware of that takes this, though I'm sure there are others. At least some newer Z-Wave ones also do (e.g., Zooz). I'm hesitant to try many of these for that reason (I'll take 3/4 of the capacity and probably won't notice; I suspect I'd notice 1/4 the capacity a bit more).
Hopefully this helps a bit. You can find what you're asking for, but IMHO, a CR2540 isn't much to be afraid of either, even though it looks like it might be--and such products might be more easily available. 
The OP was looking for contact senors. But that reminds me, the ST Multisensor is another one that uses a CR2450: https://www.amazon.com/Aeotec-SmartThings-Window-Sensor-Multipurpose. I can't think of a reason I'd prefer it over the CentraLite unless you really need the vibration or tilt sensors or happen to prefer rounder corners (or find it on sale), but it's certainly an option!
If you want something that reports temperature frequently, I suggest that you change the driver to the Zigbee Configuration reporting driver (by @kkossev , thank you!), and change the parameters to the frequency that you want. (Don't forget to hit configure, and to change back).
P.S. the Visonic MCT-370 that @bertabcd1234 mentions, does respond to this driver - but not all zigbee devices do.
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Oh geez. I saw Iris v1 and got stuck at motion sensor somehow. Ignore me.
Thank you for the info, @bertabcd1234. Honestly the only reason I’m trying to stay on CR2 is that all my battery devices use this battery and I like the idea of just having to have one battery for all my home automation. You’ve got me thinking it may be wise to consider other battery options..
You just need a "dad mode" battery case 
. That inherently means you should have supplies of every battery type under the sun "just in case."
https://www.amazon.com/dp/B089F9YDFC?ref=ppx_pop_mob_ap_share
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Look on Ebay for Xfinity XHS2-UE -- you can typically pick them up there in multiple of 5 at very low prices.
Others here have posted about them (favorably!) a lot before, but I was skeptical of the low price -- I thought surely they must have some significant flaw...
But I decided to try some out ~1 year ago, and they are indeed the real deal -- 100% reliable for me thus far (no misses, no drops) and very miserly on battery. Definitely recommend!
ETA - they aren't the most svelte contact sensors out there, so perhaps that may be a drawback, but they size-wise work fine in all applications I need them for.
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Very cool, I need 8 of them so buying in a lot for a low price is super appealing. Know if they are C8 friendly and do they report temperature?
I brought them over as part of my C7->C8 migration, and they've been rock-solid on my C8 (I wish I could say that about all my ZB devices since going to C8, but alas). So I can't speak to joining them as net-new on C8, but I wouldn't expect any issues.
They are capable of reporting temp - the "Generic Zigbee Contact Sensor" driver works great for them. I have routine temp reporting disabled as I don't really need them for that, but it's nice to know it's available. Temps seems accurate.
Snagged 10 for $35 on eBay… can’t beat that price. Excited to try them. Thank you for the suggestion!
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I have 36 of these and they're fantastic (They also do temp)
My understanding is that you like them so much you added extra windows and doors just so you could buy more. 
Rick's house below:
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If easy to switch to AAA, everyone has them. Third Reality uses them. Stay away from the Xfinity. I've resorted to throwing them away when the battery dies because the last 15 of them will not pair after battery change.
I hate them so much I want to break into all your houses and throw yours away too, but I'm fairly sure this is not the community to be breaking into. Than again, your all claiming to use Xfinity contact sensors, so I'm sure some of them are dead.
I have not had an issue with this. You mentioned this before and on several of them I replaced the battery to check things and they didn't even drop off the mesh. This is on both my c7 and c8
You're experience is very unusual...and to be clear, you should not need to pair a device after a battery change - every battery-powered Zigbee and Z-Wave device I've ever had simply re-joins the mesh after I put in a new battery. I've never seen a device fall off the mesh and refuse to re-join just from a battery change.
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@liquidskin I'm not sure why you say it's time to "pivot away from Iris V1" with the C8? Are those devices now not compatible with the C8?
I wish I could trust that they would work. I've wanted to do a weird large clock project using contact sensors as the hour markers, as well as some weird frankenswitch project using contact sensors as on off "switches" Unfortunately I only have a few left and have absolutely no faith in them.
Iris v1 devices won't pair w/the C8...they can be brought across via migration from C5/C7, but if they fall off, or if you get addtional v1 devices they won't pair w/a C8. As far as I remember HE has said they didn't see a pathway to resolve this issue.
Wow. First I've heard of this. I have a LOT of Iris V1 stuff.
@mike.maxwell is this something you guys are working on? I figured I'd eventually update to the C8 once the bugs were worked out.
