FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 11. Aircraft Electrical Systems | 2. Storage Batteries | 11-19. Battery Maintenance
9/8/98
AC 43.13-1B
e. Battery and Charger Characteristics.
The following information is provided to ac-
quaint the user with characteristics of the more
common aircraft battery and battery charger
types. Products may vary from these descrip-
tions due to different applications of available
technology. Consult the manufacturer for spe-
cific performance data.
NOTE: Under no circumstances con-
nect a lead-acid battery to a charger,
unless properly serviced.
weakening of a cell. After replacing the bad
cell with a good cell, the battery’s life can be
extended for five or more years. Full dis-
charge is not harmful to this type of battery.
(6) NiCad sealed batteries are similar in
most respects to NiCad vented batteries, but do
not normally require the addition of water.
Fully discharging the battery (to zero volts)
may cause irreversible damage to one or more
cells, leading to eventual battery failure due to
low capacity.
(1) Lead-acid vented batteries have a
two volt nominal cell voltage. Batteries are
constructed so that individual cells cannot be
removed. Occasional addition of water is re-
quired to replace water loss due to overcharg-
ing in normal service. Batteries that become
fully discharged may not accept recharge.
(2) Lead-acid sealed batteries are simi-
lar in most respects to lead-acid vented batter-
ies, but do not require the addition of water.
(3) The lead-acid battery is economical
and has extensive application, but is heavier
than an equivalent performance battery of an-
other type. The battery is capable of a high
rate of discharge and low temperature per-
formance. However, maintaining a high rate
of discharge for a period of time usually warps
the cell plates, shorting out the battery. Its
electrolyte has a moderate specific gravity, and
state of charge can be checked with a hy-
drometer.
(4) Do not use high amperage automo-
tive battery chargers to charge aircraft
batteries.
(7) The state of charge of a NiCad bat-
tery cannot be determined by measuring the
specific gravity of the potassium hydroxide
electrolyte. The electrolyte specific gravity
does not change with the state of charge. The
only accurate way to determine the state of
charge of a NiCad battery is by a measured
discharge with a NiCad battery charger and
following the manufacturer’s instructions.
After the battery has been fully charged and
allowed to stand for at least two hours, the
fluid level may be adjusted, if necessary, using
distilled or demineralized water. Because the
fluid level varies with the state of charge, wa-
ter should never be added while the battery is
installed in the aircraft. Overfilling the battery
will result in electrolyte spewage during
charging. This will cause corrosive effects on
the cell links, self-discharge of the battery, di-
lution of the electrolyte density, possible
blockage of the cell vents, and eventual cell
rupture.
(8) Lead-acid batteries are usually
charged by regulated DC voltage sources. This
allows maximum accumulation of charge in
the early part of recharging.
(5) NiCad vented batteries have a
1.2 volt nominal cell voltage. Occasional ad-
dition of distilled water is required to replace
water loss due to overcharging in normal
service. Cause of failure is usually shorting or
(9) Constant-current battery chargers
are usually provided for NiCad batteries be-
cause the NiCad cell voltage has a negative
temperature coefficient. With a constant-
voltage charging source, a NiCad battery
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