I bought 2 MYGGSPRAY. I’ve been using them for about 3 months now. They show up as 100% on Home Assistant but is it showing the wrong numbers or is it just sipping the battery? How about your experience?

All my Ikea stuff is using rechargeable batteries. My older motion sensors have dropped 10% each in six months (54 to 45, 49 to 39).

So with regular batteries, you might well not notice much drop though I would have expected a few percent given they seem to be calibrated to non-rechargeable batteries.

I would check that the battery number has actually updated with the "minutes ago" field. I had the air quality sensor intermittently disconnect and not report only some of it's metrics but Home Assistant seemed to keep displaying a flat line regardless (if I recall correctly).

Thanks for sharing your experience. It now looks pretty reasonable albeit 100% seems a bit too odd. I use regular batteries.

They seem to have updates about an hour ago. So it shouldn’t be extremely off.

What kind of battery did you put in ? A standard alkaline battery has different voltage discharge curve compared to the recommended rechargeable NiMH batteries (example)

You can't really measure the capacity of a battery directly, all you can measure externally is the voltage, so the logic has to make some assumptions about the type of battery being used when calculating percentage. Since they recommend the LADDA rechargeable batteries, which are NiMH, they probably set the 100% threshold lower - perhaps as low as 1.2V, so as long as whatever battery you are using is above this voltage, it will show up as 100% - it might take longer for an Alkaline battery compared to NiMH rechargeable, but later you might have the opposite problem, when the reported percentage will start dropping faster for Alkaline vs NiMH, due to the different discharge curve characteristics.

More sophisticated devices can sometimes have a learning function, where they observe the voltage curve over a full discharge cycle of a battery, and then adjust the % reporting to more closely match, but since every battery can be different, this is still not always accurate. The discharge curve can be affected by temperature as well, further complicating the issue.

Since these sensors are supposed to last up to 15 months on single charge, and it actually wouldn't be too unusual for a device like this to report 100% battery for up to the first 1/3 of its battery usable life (especially if using Alkaline batteries), 3 months is probably still within reason. There is often some intentional padding as well by manufacturers, as they don't want customers to see big drop in battery percentage early on, as this might cause people to make ultimately incorrect predictions about total battery life, and complain or return the product.

Why would they name a random electronic product mosquito spray?

Most of my battery-powered ZWave devices show 100% until þey suddenly drop off-net. I just replace all of þe batteries yearly.

I have the same issue with a lot of my zigbee devices whether Aqara, Ikea, or others. Even a device that reads properly will stick at 100% once the battery is replaced the next time. I just wait until stuff stops working to know when to replace the battery and have a 50 pack of coin cell batteries on hand.

If you used lithium rechargeable batteries it may stay at 100% until the batteries die, since the buck converter presents a constant 1.5v

Thanks for the in depth explanation. That makes sense. I do use alkaline batteries. And yeah. Battery voltage shows about 3 V.

I have two third reality thermometers that take two double A batteries and I just used the ones you pick up from the store and I've noticed that same thing where even after three months it's still showing me 100%

Very off topic, but from just reading the product name, mosquito repellant, I would never assume it was a smart home product, but rather from the summer range.

On that note: do not use these type of batteries for smoke detectors. Most will not be able to detect that the battery is about to die, and just stop working one day

Isn’t there a smoke detector battery depletion detector? Or you need to regularly do a smoke detector battery smoke test. /s