u/tragikarpe

Nytimes article
Nytimes recipe

Wifi Connectivity

For most connection issues, assuming it was working in the past, optimizing the router settings as seen in the photos has worked for me. But for a wifi menu specific for your router brand, I'd suggest taking the screenshot and asking a reputable LLM for settings to optimize for a iot esp32 device. A lot of the wifi 6 features and the expanded frequency channel can do more harm than good. Also important is to select a wifi channel that's less congested.

Edit: creating a separate 2G guest network does appear to work pretty well as others have suggested. Might have something to do with the router tables being full if you have a lot of IoT devices.

Pairing issues

However if it refuses to successfully pair or connect at all, then a fresh firmware and a refresh of credentials might be needed. So, you can do the moen factory reset procedure: hold the reset button until it blinks blue. Release. Hold the button and it'll go to purple, turn off, flash a little, and eventually blink blue again. Release to try pairing via the app (I'm using the new app btw). And it'll tell you connect to the sensor's own wifi AP. It will glow solid purple. After you give it your wifi credentials, it'll blink blue and purple (and it might kick you off it's wifi) but hopefully eventually will glow solid purple. That's your cue to reconnect to the sensor wifi AP to give it a final handshake. It'll beep and shut off its AP. It then may start glowing purple as it downloads the latest firmware.

If it simply continues to blink blue and purple, after maybe a minute, it'll time out on your phone and the app may erroneously claim you entered your wifi password wrong. This is a lie because it actually has no idea what happened. It's one possible reason but in my case the sensor always showed up on my network just fine. But I assume something changed on moen's backend or maybe the sensor's credentials were being rejected. Who knows. But at that point you should just factory reset and try again.

Batteries

On the subject of batteries, the worse spot the sensor is in in terms of wifi signal strength, the worse the battery life. This is because the esp32 has to increase the transmission power to check in with the router every 1 to 2 hours, which can add up.

If you opt for a rechargeable solution (and you probably should), you should get one with a guaranteed 3V output. This means the battery will come with a built in buck converter to regulate the voltage. Be sure to verify it actually does this with a multimeter because if it doesn't, it could fry your device. And some unreputable batteries have been seen outputting as high as 4V. You won't be finding any major brand names here so you'll have to instead go with a trusted battery vender. (I had good luck with 16340 KeepPower 1000mAh from illumn) but hopefully more players will enter this space in the future. 16340 is the size of the battery you'll be searching for. (Edit: they can also be listed under size RCR123a, which is what the parametrek battery finder does. As you can see, your options are quite limited for a 3V output)

Low battery warning

One thing to note about these rechargeables is that since the output is locked in at 3V, then it'll be hard judge how much energy remains. When the battery voltage dips under 3V, then you have roughly a day or less of battery life remaining and should be charged immediately. Luckily, the moen Flo app had the foresight of allowing you to dictate the percentage of battery at which to alert "low battery". Set it at 99%. This will give you maybe a day's advance warning before it drops dead. Edit: if you set it too low like at 10% (which would be fine for a disposable cr123a), your device will die before it can send out a low battery alert because the voltage drops too rapidly upon battery depletion for the 3V rechargeable.

Plugged in solution (at your own risk?)

In my case, my 3v output came with a built in usb port for charging. If a multimeter verifies that it outputs 3V even while plugged in for charging, then you can try to see if you can keep the battery plugged in indefinitely while in the leak detector. Check (by feeling it) the battery temperature in an hour and if it remains at room temperature and is not hot (and the voltage still remains at 3V), then you should probably be fine? Edit: to be clear, this is almost definitely against manufacturer recommendations so do this at your own risk. Make sure you use a reputable usb charger. And definitely don't try this with high drain devices like flashlights etc. Only reason you can get away with this here is because the esp32s are low drain.

The esp32 isn't exactly all that power hungry. It just feels that way because it's expected to connect to wifi every other hour and live off of a single cr123a. A bigger battery pack would've been nice. Unfortunately you can't keep the cover on with the charging cable stuck to the battery so either leave it off or maybe drill a neat hole for it.

Trade-offs and possible mitigation

Since the voltage output is locked at 3V, the leak detector should be protected and the worst case scenario would be depletion of battery life of your rechargeable battery ​due to being at 100% capacity all the time. As you may know, lithium ion batteries do not like being at 100% charge constantly. You could mitigate this by setting up some sort of timer or smart outlet that turns on to charge the battery every few weeks or so but I'm not sure if it's worth the effort.

Anyways hope this helps a little.