Tradfri products

[JDRoberts]

@Declankh

In my experience the battery percentage reported by zigbee devices is not very reliable. I think it guess battery level by voltage drop and the voltage drop is non linear.
I’ve put brand new batteries in that report less than 100 percent from the beginning.

It’s fairly linear for non-rechargeables. What’s probably more significant is that many devices report battery level in tiers.

FAQ: How Sleepy Devices Report Battery Life (tier reporting)

Many battery-powered " sleepy" devices reports battery levels in tiers. The exact tiers will vary by device. For most contact sensors, the tier that is reported as “88%” really means “above 87% and below 100%” So as soon as battery level drops below 100%, even to 99%, it will likely be reported by SmartThings as 88%, although the exact buckets vary by DTH/Edge Driver. What you need to watch is the trend. If it drops 10% in one day. That was probably just a tier drop. You can even bounce back-and-forth by 10% because it’s right at the threshold of a tier. But if it’s dropping 10% every week, that’s a different problem. If you’ve had any device off-line for a while, it’s really common for it to come back in the next lower tier, which looks like a 10% drop but might’ve been a drop of ha…