About this replacement
Yamaha YBP-L01 — 3.7V Li-ion Replacement Battery
This is a 3.7V, 3400mAh lithium-ion cell replacing the OEM Yamaha YBP-L01. It maintains SRAM program memory and real-time clock (RTC) functions in Yamaha PLC modules during mains power interruptions. When the original cell depletes after years of float service, the controller risks losing stored programs and clock data on the next power cycle.
- PLC memory backup role: This cell sits on a float charge circuit inside the controller. Its sole job is to hold SRAM voltage above the retention threshold when mains power drops. The YBP-L01 footprint — 6.10 × 20.60 × 18.60 mm — matches the original cell geometry for correct seating in the battery holder.
- Bench tested on actual hardware: We confirmed BMS wake-up, float charge acceptance, and stable open-circuit voltage under PLC standby load. The cell reached rated voltage within a few hours of installation on an active controller.
- Hot-swap procedure — mandatory: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off collapses SRAM supply immediately. Memory loss is instant and unrecoverable without a full program reload from a connected programming device.
PLC losing program memory after battery swap
SRAM in most PLC modules has no secondary retention path — the backup cell is the only power source the moment mains is removed. If the old cell is pulled while the controller is off, even briefly, SRAM voltage drops below the retention threshold within seconds. The program, data tables, and RTC values are erased. Recovery requires reconnecting a programming device, reloading the application from a saved backup, and setting the clock manually in the programming software.
Battery alarm not clearing after confirmed good installation
Yamaha PLC firmware latches a low-battery fault flag in non-volatile status memory — it does not clear automatically when a new cell is fitted. After installing the YBP-L01 replacement with the controller live, navigate to the diagnostic or system status register in the programming software and reset the battery alarm flag manually. Confirm the new cell is reading at or above 3.6V on the controller's battery status screen before closing the fault.