Yamaha YBP-L01 PLC Backup Compatible Battery 3.7V 2600mAh

Yamaha YBP-L01 — 3.7V Li-ion PLC Backup Battery

This is a 3.7V, 2600mAh (9.62Wh) lithium-ion cell for Yamaha PLC systems that use the YBP-L01. It maintains SRAM program memory and the real-time clock during power outages and scheduled maintenance. When this cell degrades, the controller loses its program and clock data the moment mains power drops.

• Yamaha PLC memory backup application: The YBP-L01 sits on a float charge from the PLC's internal power rail, supplying just enough current to hold SRAM state and RTC registers when the controller is de-energised. It is not a run battery — it does nothing while the PLC has mains power, which is why cell degradation often goes unnoticed until a power event exposes it.
• Bench tested on actual hardware: We charged the cell to 4.2V, held it at storage voltage, then confirmed BMS protection tripped correctly at under-voltage. Float acceptance current measured within spec, confirming the cell will charge normally once seated in the PLC's battery bay.
• Hot-swap procedure — mandatory for this controller: Always replace this battery with the PLC powered on and in RUN mode. Removing the old cell while the controller is off cuts SRAM supply immediately. If that happens, the full program must be reloaded from a programming device before the controller will run again.

PLC losing program memory after battery swap

SRAM in a Yamaha PLC holds program data only as long as it receives continuous voltage — either from mains through the internal power supply, or from the backup cell. The instant both sources are absent simultaneously, SRAM content is gone. This is why swapping the cell with the controller powered off is the single most common cause of a blank controller after a routine battery change. If memory loss has already occurred, reconnect the programming device, reload the project file, and re-initialise any retain data areas before restarting production.

Battery alarm not clearing after a confirmed good installation

Yamaha PLC battery alarms do not clear automatically when a new cell is detected — the controller latches the fault flag until it is explicitly acknowledged. After fitting the new YBP-L01, open the programming software, navigate to the system diagnostic or alarm log, and manually reset the battery fault bit. If the alarm returns within hours, check that the cell is seated correctly and that the connector is fully engaged, then confirm float charge voltage at the battery terminals reads between 3.9V and 4.2V.