TELink TLSR827 Series Manual page 23

2.8 V ≤ VDD < 2.9 V
2.7 V ≤ VDD < 2.8 V
2.6 V ≤ VDD < 2.7 V
2.5 V ≤ VDD < 2.6 V
2.4 V ≤ VDD ≤ 2.5 V
2.3 V ≤ VDD < 2.4 V
2.2 V ≤ VDD < 2.3 V
2.0 V ≤ VDD < 2.2 V
VDD < 2.0 V
Note

The RCU will report battery level after successful pairing of the first time, or if battery voltage changes
in connection state. And during reconnection, as per the software design, the RCU will report battery
level only if it's less than 100%.

The battery voltage detected via ADC may have about 50mV deviation
PS-20033000-E1
Spec For TLSR827x-based BLE Audio Remote Control
90%
80%
70%
60%
40%
20%
10%
dead
22
0%
Ver.0.1.0