The cells of the battery contain only a small amount of electrolyte. The electrolyte 
level should be checked only after the battery has been charged and water added as required, 
taking care not to overfill. Even in the fully charged condition, the level should be no higher 
than the red line which, in some types of cell, is only slightly above the plate tops. The 
reserve electrolyte type of cell construction has two red lines marked on the cell jar. The 
electrolyte level should be maintained between these red lines when the battery is in the 
charged condition. Whenever water is added, thoroughly soak and rinse the removed vent 
plugs with water before replacing. Very little water will be consumed if the battery is on 
constant trickle or float charge at the proper voltage. 
In very small cells there is not sufficient electrolyte to take hydrometer readings. 
After some time in severe cycle service where electrolyte specific gravity is in doubt, invert 
the battery, draining all free electrolyte. Replace with new electrolyte of 1.300 specific 
gravity, which should be obtained only from the manufacturer. 
When charging at high rates, the cells will gas rather vigorously when approaching 
full charge. This gassing will cause the electrolyte level to rise above the red line. This 
apparent excess electrolyte should not be removed as the level will drop back after the cells 
stand on open circuit following the charge. 
A white crystalline deposit may appear on the cell tops. This is potassium car- 
bonate which is noncorrosive and harmless. This should merely be brushed or washed off 
periodically. 
Maintain the battery in a clean and dry condition externally. Carefully wipe off 
any spilled liquid. 
WARNING: Sulfuric acid, as used in lead-acid batteries, will cause permanent damage to 
NICAD batteries. Therefore, do not add sulfuric acid to NICAD cells and do not use any tools, 
such as hydrometers or funnels, which have previously been used with lead-acid batteries. 
Care should be taken to keep open flames or sparks from the battery particularly 
when it is on charge, as there is the possibility of hydrogen gas being generated in the elec- 
trolysis of water and the resulting danger of an explosion. 
Do not spill electrolyte on clothes or the skin. In case of accident, wash with 
vinegar or saturated boric acid solution and rinse freely with water. 
5. READOUT EQUIPMENT 
5.1 RUDDER CHANNEL 
5.1.1 Position 
The alignment of the control and readout potentiometers on the servo unit is 
described in Section IV, 3.1.3. Information as to the adjustment of the telemetering equipment 
is described in the calibrating procedure, Section III, 2.2.2, and in Section IV, 2, which covers 
maintenance of telemetering equipment. 
IV-8 
