Honeywell HC900 Manual De Usuario

Removal and Replacement Procedures - Safety Considerations - PLAN AHEAD! 

152 

  HC900 Hybrid Controller Installation and User Guide 

Revision 5 

  

9/03 

Memory for the CPU in the Controller Module includes: 

• 

Volatile memory and 

• 

Non-volatile memory (Flash) 

Only volatile RAM requires battery backup. 

When power is applied to the Controller Module, the CPU is initialized automatically.  If the battery is 
installed after initialization, and if site power is maintained, the current draw from the battery is very low - 
approximately 4 microamps.  If site power is disconnected with the battery in place and with the CPU in 
the initialized state, the current draw on the battery is approximately 800 microamps.  However, if the 
battery is installed before power is applied (and the CPU initializes), the SDRAM will draw approximately 
40 milliamps. 

At the 4 microamp level, the battery will retain energy over an extended period. 

At the 800 microamp level, the battery will retain sufficient energy to maintain the content of SDRAM for 
50 weekends (approximately 100 days) of backup service. 

At the 40 milliamp level, battery life is severely reduced.  The battery could be rendered useless in less than 
60 hours. 

 

Do not install or replace the backup battery until after site power is applied.