CONTACTOR-PRESSURE 7C3664 - Caterpillar

All Engines Equipped With Woodward Model 2301 Governors And 32 Volt Electrical SystemsThis article is a reprint of the article in Engine News, September 19, 1979, on Pages 5 and 6.
When an engine is equipped with a Woodward Model 2301 Governor and a 32 volt electrical system, the battery charging voltage must be limited to a maximum of 40 volts. Any voltage higher than 40 volts in the system can cause governor failure. This has been a problem in some electrical systems, especially where nickel-cadmium batteries are used.
Most installations of nickel-cadmium batteries use 25 cells for a 32 volt electrical system, and the voltage necessary for charging is 36.5 to 37.5 volts. Since this voltage is very near the maximum of 40 volts permissible for the Woodward governor, it must be carefully controlled to prevent governor damage. During battery charging, the output voltage of the charger is not exactly constant, but increases and decreases rapidly in a range a little above and below the average charging voltage. This normal range of voltage is known as "ripple" voltage, and can cause damage if the range extends too far above the maximum charging voltage.
There are two primary factors which have an effect on the range of "ripple" voltage. The first is the size of the battery charger in relation to the battery capacity. If a 10 ampere charger is used with a 25 cell battery that has a capacity of 125 ampere-hours at an eight hour rate, the "ripple" voltage can go above 39 volts. For this reason, the recommendation is to use a charger no larger than 5 ampere with a battery of this capacity. If the charger used has a setting for "fast charge" or "equalizing charge", this setting must never be used because the voltage is higher than 40 volts.
The second factor in the control of "ripple" voltage is battery maintenance. The level of electrolyte in the battery cells must be checked regularly and water added when necessary. A low level of electrolyte in the battery cells decreases the load on the charger and permits the range of the "ripple" voltage to increase.