MKS 651C - Expected Battery Life; Battery Storage; Table 19: Expected Battery Life; Table 20: Capacity Loss of Stored Battery

Expected Battery Life Cha
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Expected Battery Life
When AC power is lost, the valve battery backup drives the valve to full open or full closed
within 20 seconds. An AC power failure typically results in a 30% discharge of the battery.
Under this condition, the battery life is at least 1000 cycles, and should be able to recharge within
a few hours after power returns. Battery life under several conditions is listed in
Table 19.
Expected Battery Life
Expected Cycles % Discharge with each Battery Use
1000 30
400 50
200 100
2-3 years if unused and charge is maintained
Table 19: Expected Battery Life
When AC power returns, the battery recharges, provided that the 651 instrument is turned on.
From a full discharge condition, the voltage typically increases from about 11 V to 15.5 V over a
five hour period. The voltage is maintained at about 14.5 V for another five hours then gradually
drops to 13.5 V. The 13.5 Volt charge is maintained in a trickle charge state (a top charged state)
until there is an AC power failure. The recharge time for a completely discharged battery is a
maximum of 12 hours.
Battery Storage
The lead-acid battery loses its capacity if it is stored with no power connected. In fact, the higher
the ambient temperature, the faster the capacity is lost. Table 20 shows the time it takes for the
battery to fall to fifty percent of its full capacity at various ambient temperatures.
Capacity Loss of Stored Battery
Ambient Temperature (° C) No. Days to 50% Capacity
20 500
30 250
40 150
50 75
Table 20: Capacity Loss of Stored Battery