Riester 3.5V XL Compatible Battery 10691 3.7V 2600mAh

Riester 3.5V XL Series — 3.7V Li-ion Replacement Battery (10691)

This 3.7V, 2600mAh Li-ion battery replaces the OEM 10691 cell in Riester diagnostic instruments including the 3.5V XL, Led Li-Ion handles, C Handles, and 3.5 Ri Accu C Type Handle. These are handheld medical examination devices — otoscopes and ophthalmoscopes used in clinical settings for ear and eye inspection. Voltage and capacity match the original specification exactly.

• C Handle and XL platform compatibility: These Riester handle variants share the same cylindrical cell format, 3.7V nominal voltage rail, and BMS connector pinout. One battery covers all listed models without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on Riester handle hardware. The BMS accepted the cell without fault codes, and the charge IC completed normally to full capacity within expected parameters.
• Power-on self-test after installation: After fitting this battery, let the device complete its full startup self-test without switching it off. Medical device firmware runs a BMS verification sequence at power-on — interrupting it logs a false battery fault that persists until the next clean reboot cycle.

Charge indicator not reaching 100% on the first charge cycle

Riester handles use a conservative charge IC that applies a reduced current limit when it detects a new or unfamiliar cell. This is intentional — the IC performs a capacity verification pass before committing to a full charge. On the first cycle, the indicator may plateau at 90–95% before the session ends. Run one complete charge-discharge cycle and the IC recalibrates to the full 2600mAh capacity, after which the indicator reaches 100% normally.

Device alarms low battery immediately after a confirmed full charge

This happens when the device firmware compares resting cell voltage against a threshold calibrated to an aged OEM cell. A new Li-ion cell at full charge can sit slightly above the voltage curve the BMS expects, and some firmware versions misread this as an out-of-range value. Run one full charge-discharge cycle before clinical use — this allows the BMS to complete its learn cycle and align the state-of-charge estimate correctly. After that single cycle, the low-battery alarm clears and does not return.