Application Scenarios:

During a scheduled full plant power-down for maintenance at a water treatment facility, the ABB AC 800M controller racks are completely de-energized. Without protection, the controllers would lose all their running programs, tuned parameters, and network configuration stored in volatile RAM, requiring a lengthy and error-prone restoration from backups. The ABB SB821 3.6V Lithium Battery Unit​ is the essential safeguard. Installed directly on the controller’s CPU module or within the system rack, this battery unit provides a continuous, low-current 3.6V supply to the memory circuits. During the hours-long power outage, the SB821​ invisibly maintains the memory’s state. When power is restored, the controllers boot up seamlessly with all their application logic and settings intact, as if they were never turned off. This eliminates the risk of a corrupted restart, prevents hours of recommissioning work, and ensures the plant can be brought back online quickly and safely, directly addressing the critical need for data persistence in modern electronic control systems.

 

 

Parameter:

Main Parameters	Value/Description
Product Model​	SB821​
Manufacturer​	ABB
Product Category​	Memory Backup Battery Unit / Lithium Battery Pack
Nominal Voltage​	3.6 VDC​ (Lithium chemistry, e.g., Lithium Thionyl Chloride Li-SOCl₂).
Typical Capacity​	1.2 Ah to 2.4 Ah (providing backup for months or years). [Key for lifespan]
Primary Function​	Provides continuous backup power to volatile memory (RAM) and real-time clocks.
Compatible Systems​	ABB AC 800M PM/BA units, S800 I/O communication modules (e.g., CI854), other ABB controllers.
Connection Type​	Wire leads with connector, or direct plug/socket to the host module.
Operating Temperature​	Wide range, typically -40°C to +85°C, suitable for industrial environments.
Shelf Life / Service Life​	Very long shelf life (10+ years), with operational backup life of 3-5 years typically.
Key Feature​	Extremely low self-discharge rate, maintaining charge and voltage stability for years.

 

 

 

Technical Principles and Innovative Values:

The SB821​ leverages advanced lithium chemistry to deliver unmatched reliability for a mission-critical but often overlooked function.

Innovation Point 1: Lithium Thionyl Chloride (Li-SOCl₂) Chemistry:​ This battery chemistry is chosen for its exceptional properties: an extremely low self-discharge rate​ (often less than 1% per year) and a very flat discharge curve. This means the SB821​ maintains a nearly constant 3.6V output throughout almost its entire service life, providing stable voltage to the memory circuits, and then signals an “End-of-Life” voltage drop relatively quickly, giving clear warning for replacement. This is superior to older Ni-Cd or standard lithium-ion packs for this application.