BATTERY SPECIFIC GRAVITY TEST

TM 10-3930-623-12

shown in wiring diagram, figure 1-11. Observe all

Voltage Adjustment.

To adjust the voltage

precautions given in paragraph 5-35 to prevent damage

regulator setting, remove the access plug from the

to diodes and windings.

regulator. Then for an undercharged battery insert

screwdriver into slot and turn clockwise one notch (0.3

5-36.

SETTING

VOLTAGE

REGULATOR

volt) to increase the setting. For an overcharged battery,

BATTERY NEEDS.

turn counterclockwise one notch (0.3 volt) to decrease

setting. Then check for an improved battery condition

1. The desired voltage regulator setting is one which

keeps the battery in a satisfactory state of charge (3/4

over a service period of reasonable length. If necessary,

charge or more) without causing excessive battery

repeat the above procedure for a higher or lower setting.

overcharge (as evidenced by excessive battery water

usage). However, if operating service conditions are

4. Removal.

above or below average, the voltage regulator setting

must be adjusted or tailored to adapt it to the battery and

a. Disconnect negative battery cable from battery

type of service conditions. Either of two conditions may

persistently exist which indicate the need for adjusting

post (para 6-47).

the regulator setting: either battery is being overcharged,

or battery remains undercharged. Corrections should be

b. Tag and disconnect alternator and battery leads

made as follows:

at the voltage regulator (fig. 6-3 ).

a. If the battery uses too much water at the normal

c. Remove capscrews and lockwashers that

setting, reduce the voltage setting approximately 0.3 volt

secure the regulator to the mounting bracket and remove

and check for decreased battery water usage over a

reasonable period. If necessary, repeat this process

regulator.

until the battery remains charged with a minimum use of

water.

5. Installation. Reverse removal procedure and install

the voltage regulator.

b. If the battery is consistently undercharged

(evidenced by inability to crank the engine) at the normal

5-37. BATTERY SPECIFIC GRAVITY TEST. Specific

setting, increase the voltage setting 0.3 volt and check

for improved condition over a reasonable service period.

gravity testing of the battery electrolyte determines the

If necessary, repeat this process until the battery

state of charge in each battery cell. Use a hydrometer

remains charged with a minimum use of water.

and thermometer, correcting the hydrometer reading for

temperature. A corrected specific gravity reading of

2. Batteries which do not respond to the voltage

1.260 to 1.280 in each cell indicates a fully charged

settings within the specified range of this regulator

battery. A specific gravity reading of 1.2220 or less in

usually will be found to be batteries used in vehicles that

each cell indicates that the battery must be recharged or

are operated consistently at low speeds or that have

added electrical loads to the original electrical system, or

replaced.

batteries that have been improperly activated.

NOTE

a. When a vehicle is operated consistently at low

speed and/or electrical loads have been added to the

A temperature corrected specific

original electrical system, the battery may remain

gravity measurement is obtained by

undercharged even with the regulator placed in its

adding

0.004

the

actual

maximum setting. Under these conditions, alternator

output or charging time may be insufficient to offset the

hydrometer reading for each 10

electrical load on the battery. Periodic recharging of the

degrees F the electrolyte is above 80

battery from an outside source of replacement of the

degrees F, or subtracting 0.004 from

original alternator with a special extra-output alternator

the actual hydrometer reading for

will be required in these cases.

each 10 degrees F the electrolyte is

below 80 degrees F.

b. Replacement batteries suspected of having

been improperly activated should be removed for a

complete check. If the specific gravity at full charge is

5-38. BATTERY CLEANING. The top of the battery

less than 1.230 in any cell, the battery has either been

must be kept clean. Tighten vent plugs and clean

improperly activated or is worn out and, in either case,

battery with a brush dipped in a solution of baking soda

will give poor performance. If the specific gravity is

and water, followed by a thorough rinse with clear water.

above 1.310 in any cell, the battery has either been filled

If terminals and cable clamps are corroded, disconnect

with electrolyte of too high specific gravity or electrolyte

cables and clean in same manner as battery.

has been added in place of water. Either situation is

harmful to the battery and will cause early failure.

5-12/13/14