1-8S Low voltage buzzer alternatives?

Hi guys,
I purchased a 1S To 8S Low Voltage Buzzer Alarm 2 in1 Lipo Battery Voltage Tester Volt Meter Indicator Checker Dual Speaker 2S 3S 4S 8S
from AliExpress .
Its specs are mentioned below:
- Use for 1-8S Lipo/LiMn/Li-Fe
- Voltage detection precision 0.01V
- Unit voltage display range 0.5-4.5V
- Total voltage display range: 0.5 - 36V
- 1S test mode voltage range: 3.7-30V
- Low voltage alarm mode for 2-8S
- Alarm set value range: OFF-2.7-3.8V

However, when I use them with my battery pack, I am getting voltage errors upto 0.1v. It gives a false indication and it cannot be calibrated as well.
Does anyone know how to calibrate them or suggest any alternatives to it?

checkt out the ISDT BG-8s, not as cheap but can do a lot more