Right Half Battery Percentage Drops from 100% to 85% Immediately After Unplugging
I'm experiencing an issue with my Corne (split) keyboard where the right half reports 100% battery while plugged in, but as soon as I unplug it, the battery percentage immediately drops to 85% within about a minute.
Details:
Right half behaviour:
Shows 100% while charging
Drops to 85% within a minute after being unplugged
After this drop, the percentage seems stable
Left vs right battery life:
Right half appears to last longer than the left
I haven't done full drain cycle tests yet, but the right half easily lasts a full day without needing to recharge
Firmware / config changes:
I edited my ZMK config to increase Bluetooth transmit power because I had connectivity issues on my home PC
No connection issues with work laptops
Not sure if this affects the battery
My question:
Is this behaviour normal for the battery gauge on the right half?
Is there a way to reset or recalibrate the value so the right side correctly reports 100% when fully charged?
Or is 85% a fixed upper value for battery reporting depending on the specific board, regulator, or battery used?
Confirming I'm using the battery provided on the typeractive website.
Thanks in advance.
1 Reply
What you’re seeing is normal for these boards and batteries.
On ZMK (and on our Corne specifically), the “battery %” is just an estimate derived from voltage, not a smart fuel gauge. While plugged in, the cell is held at a higher charge voltage, so the firmware reports ~100%. As soon as you unplug:
- The voltage immediately sags to its resting level
- The estimate recalculates and often lands in the 80–90% range
- After that, it usually tracks down more slowly and consistently From our battery guide:
- The estimate recalculates and often lands in the 80–90% range
- After that, it usually tracks down more slowly and consistently From our battery guide:
The reported battery percentage is not accurate… Your battery may never reach exactly 100%, and it's not a cause for concern, as long as it gets to at least ~80%.Your right half lasting longer than the left is also expected: the left is the “central” half and uses more power. Increasing TX power in your ZMK config will reduce battery life somewhat, but it doesn’t change this initial 100 → ~85% jump; that’s just how voltage-based estimates behave with these LiPos. There isn’t a real “recalibration” to run, and 85% isn’t a hard cap—just where your particular cell/board combo falls once it’s off the charger. As long as: - The right half runs for a good amount of time (which it does), and - It charges normally, you’re in good shape. If you want, you can share your actual runtimes or config by replying to this message or tagging me and I can sanity‑check further.