MKS 651D Series, User Manual, Page: 46 / 162

Optional Valve Failsafe Battery Back-Up Chapter Three: Overview
34
Optional Valve Failsafe Battery Back-Up
The optional valve failsafe battery back-up provides full valve drive capability for about 30
seconds after an AC power failure. The 651 controller can be set to drive the valve open,
closed, or disabled. When in a disabled state, backup power is not provided. In most cases this
means that the value doesn’t move, but this is not guaranteed.
This battery is a rechargeable, 12 Volt, 2 amp-hour, sealed lead-acid battery (MKS part no.
003-1109451). If the battery backup is installed, an
ATTENTION
label is affixed to the side of
the 651 unit stating that it contains a lead-acid battery.
Note The lead-acid battery is also available from the following sources:
•
Power Sonics (PS-1220)
•
Panasonic (LCR 12 V2.2P)
Battery Voltage
The normal voltage level of the battery ranges from 11 V to 15.5 V. A voltage level below 11 V
indicates a discharged battery. A voltage level above 15.5 V indicates an open fuse, a
disconnected battery, or a defective charger.
The battery is continually recharged while the 651 unit is powered and operating. Therefore, the
battery is typically maintenance free and only needs attention when it must be replaced. Refer to
1, page for more information.
Valve Positions
The controller can be configured so that the valve will be driven fully open, fully closed, or will
be disabled upon an AC power failure.
Open: The controller opens the valve at power down. In the event that the valve is already
open, the module provides power for approximately 1 second before turning off.
Closed: The controller closes the valve at power down. In the event that the valve is already
closed, the module provides power for approximately 1 second before turning off.
Disable: The option is disabled and will not perform any function at power down. The
controller turns off in a normal manner.
When the controller is configured to open or close the valve, it will perform the operation
whenever power to the controller is turned off, regardless of whether the power is turned off via
the power switch or by a power failure.