MOTOR TRUCK SERVICE MANUALELECTRICAL
Precautions When Working Around Batteries
f a worn-out, corroded or undersize cable. Faulty battery
performance may indicate cable trouble.
It cannot be stressed too strongly that there are
PROPERTIES OF ELECTROLYTE
certain dangers involved in working with or around lead-
acid batteries. Care should be taken to avoid these
pecific Gravity Affects Freeze Point
dangers.
Specific gravity of the electrolyte determines the
1. Electrolyte is a combination of water and sulfuric acid
temperature at which a battery will be harmed or
and as such is dangerous to clothing, vehicle parts
damaged by freezing.
and human skin-and especially dangerous to the
eyes. Take care to avoid slopping or spilling acid
Chart D which follows gives the freezing point of
when reading hydrometers or filling batteries. Acid
battery electrolyte at given specific gravities.
on the skin should be washed off with cold water and
soap as soon as possible. Eyes should be
immediately washed with cold water and a physician
Electrolyte Specific Gravity
Freezing Point (F)
90 below 0
notified.
1.280
1.265
75 below 0
NOTE: Use only distilled water or odorless,
1.220
30 below 0
colorless and tasteless drinking water in a storage
1.210
20 below 0
battery. Patent electrolytes or battery dopes are
1.180
10 below 0
injurious and void the battery guarantee.
0
1.160
1.140
10 above 0
2. Never smoke or bring a flame close to batteries.
1.100
20 above 0
The gas given off during charging is hydrogen, which
1.000
32 above 0
is extremely explosive in the presence of a spark or
flame, Fig. 18. Never check the condition of a
CHART D
battery by shorting between terminals, and for
safety's sake never lay tools or other metal objects
Temperature Affects Battery Capacity
on top of a battery where they might short between
terminals or short between ground and the
The battery container is a good heat insulator, and
ungrounded terminal. Always remember that one
the electrolyte temperature will lag several hours behind
side of the battery is grounded to the frame of the
atmospheric temperature.
vehicle and when working on other electrical
components, it is best to remove the ground side of
The specific gravity of the electrolyte (distilled water
the battery first.
and acid solution) must be maintained at 1.225
minimum, and the level of the solution should be at the
indicator level in the battery cover. A fully charged
battery has a specific gravity of 1.255- 1.270 at 80 F.
To eliminate the possibility of harmful sulfation of
plates, a battery with a specific gravity of 1.225 or less
should be recharged.
The following chart (E) shows the effect of
temperature on the capacity of a battery.
State of
Electrolyte
Percentage
Charge
Temperature (F)
Capacity
Full
80 above 0
100
60 above 0
Full
88
Full
40 above 0
75
20 above 0
Full
62
Full
0
45
20 below 0
Full
20
Fig. 18 Explosion Caused by Open Flame Near Battery
CHART E
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