OPERATING PROCEDURES FOR MODEL MBC8 BATTERY CHARGER (cont)

OPERATING PROCEDURES FOR MODEL MBC8 BATTERY CHARGER

THEORY OF OPERATION MODEL MBC8 BATTERY CHARGER

TM-55-1930-209-14P-9-4 Water Purification Barges (NSN 1930-01-234-2165) Electric Power System Manual
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OPERATING PROCEDURES FOR MODEL MBC8 BATTERY CHARGER (Continued) BATTERY CONDITION - A fully charged battery will be indicated by a low Charger output current and, for lead acid batteries, a full charge specific gravity hydrometer reading in all cells. A battery which has approached end of life will have a reduced ampere hour capacity (something less than the battery's rated capacity). An adequate check of a battery for capacity in an engine starting application is to monitor the battery voltage while it is cranking the engine during an expected worst case starting attempt. If the battery was fully charged its cranking voltage should be more than 75% of nominal voltage (9 volts minimum on a 12 volt lead acid battery). Batteries which have sufficient capacity but which are not fully charged may not pass this test. Similarly, worst case voltage drop can be established for other high current load application to determine the battery condition assuming that the battery is fully charged. TO PUT THE CHARGER INTO OPERATION - Connect per installation instructions and apply A.C. power. CAUTION: Always disconnect, turn off, or remove A.C. power from the Charger before attempting to service the Charger or before connecting or disconnecting Charger or battery leads. Similarly, do not connect or disconnect battery leads with any loads connected. NORMAL OPERATION - When power is first applied the Charger will normally supply at least rated current as indicated on the Charger ammeter. As the battery charge builds up the charge current will reduce finally to a level required to maintain the battery charge and supply any additional loads. The charge current should reduce to lower values within 30 hours or less for properly sized Chargers. When a drain is put on the battery or A .C. power is interrupted the Charger will again produce higher output currents until the battery voltage builds up to a charged condition. When connected to a fully discharged battery the charge current will be higher than rated current for part of the charge cycle. As above, a deep discharged battery can cause Charger shutdown (if its terminal voltage is less than +5.0 volts) for up to several hours before high charge currents to occur as above. Note that for a deep discharged battery to eventually allow Charger turn on, there must be no other loads on the Charger (or battery). CHARGER MAINTENANCE - There are no field adjustments to be made on these Chargers. The only adjustable device is the float voltage adjustment on the regulator P.C. board which is factory set using precision equipment. LOW VOLTAGE SHUTDOWN - These Chargers are normally supplied with low voltage shutdown which causes the Charger to reduce its output current any time the battery output terminal voltage drops below +5.0 volts. The Charger will shut off completely if the output terminal voltage drops below +2.5 volts. This provides reverse polarity and short circuit protection. In addition, in the absence of capacitive loads, the Charger will shutdown on "missing battery" or open leads, if the Charger output terminals (+B & -B) have 3.0K ohms or less of load resistance connected. MBC8B 2 of 2

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