Finally ran out of existing batteries laying around for my sensors that didn’t include batteries. Need mostly AAA right now but in future will also need the coin cell.
Rechargeable can screw with battery reporting, right? But will it actually last any longer/shorter?
If going with alkaline do I really need to try and go for more premium/name brand or will super cheap do just fine?
Like a lot of things, I think whenever you can it pays to try something new in a small way, find out what works for your setup, then look to apply it more broadly. Given the sometimes broad range of performance in things like batteries, and the cost that can come from a poor choice, I think it makes sense.
I have Philips Hue indoor motion sensors quite happily running on rechargeable AAA batteries, even though they suggest the higher-grade batteries. I've had mixed experience with some cheaper options for coin batteries, so I think these in particular are worth investigating.
If you have a hunt around on the Community there was a discussion in the last 18 months or so about peoples experiences with different battery brands, which may help you narrow down your choices.
I buy rechargeable as much as I can. They don’t last anywhere as long as non-rechargeable however.
When I buy either, I look for the highest mili Amp Hour (mAh) value as possible.
I switched to rechargeable CR-2s for my Iris v2 contact sensors, but I still use single use CR-2s for my Iris v2 motion sensors - I found the low-battery behavior of the motion sensors not very good, and they went through the batteries much faster.
Here's a comparison from when I switched:
How do you find the battery reporting/handling of them?
I’m okay (I think?) with inaccurate battery reporting, but I sort of don’t want a “50%” report one day and totally dead the next 
I have never used battery reporting. When the sensor stops reporting, I change its battery.
I use Device Activity check to know when that happens.
Interesting, although the whole way it works is "too late" in a way... which is annoying, but perhaps more foolproof.
But what about if you leave for the weekend? Or even a vacation, or other multi-day trip? None of your sensors will trigger
I use these exclusively now.
I’m in agreement with @Sebastien in regard to battery reporting. I do now use an app that works with HomeKit reporting to get a rough idea. All of the sensors will never go off line at once due to battery levels. So if you go away and you lose a sensor 
For the rest that use CR2, CR123A, CR1632, CR2032 and CR2450, I use Panasonic or whatever is reasonably priced at the time I need to order.
I just posted elsewhere about my recent Ray-O-Vac AA battery experience. Three of them leaked all over the insides of a Utilitech z-wave leak sensor (that I'm trying to get back on line...don't ask...well, I'll say: I think I pushed a button too many times and excluded...whatever...I'll get it back.
Anyway, I was kind of doing a test, to see if it would give out a battery low warning. Again, whatever, it didn't and just ran down. The last reading a week ago was 1.
I'm thinking, from my limited experience here, that running your alkaline batteries to the point they are totally flat might not be the best idea, especially if you skimp on batteries.
I have never found battery reporting to be reliable for any of my smart home devices, whether they’re using alkaline, rechargeable or (non-rechargeable) lithium batteries.
I have always assumed that due to battery chemistry, it’s just a totally different experience than what we’re all used to from the rechargeable lithium-ion batteries in our phones, tablets and laptops.
I've been getting a low battery notice the last couple of days on an Ecolink z-wave contact sensor mounted outdoors in a box. It was down to 20% I think I'll change it while the weather is warm, since it's a hassle. It's a 'fancy' 1/3 size battery, whatever the designator is. Only been 6 months, but as I said, replacement would be a hassle in the super cold and it's nice to know if the gate is open or closed.
^^THIS^^
I guess it’s the most “trusted” solution, but isn’t it annoying to have something “suddenly” stop working?
I think most people would opt for reliable battery reporting if possible.
But it’s hard to argue with chemistry.
Bah… It depends on the automation. In some cases, it is. Then I check the battery report… 
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