homeassistant

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).

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.

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

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.

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%

Why would they name a random electronic product mosquito spray?

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.

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