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 | 11-20. Electrolyte Spillage
AC 43.13-1B
9/8/98
having a shorted cell might overheat due to ex-
cessive overcharge and undergo a thermal run-
away, destroying the battery and creating a
possible safety hazard to the aircraft.
g. Aircraft Battery Inspection.
(1) Inspect battery sump jar and lines
for condition and security.
DEFINITION: Thermal runaway can
result in a chemical fire and/or explo-
sion of the NiCad battery under re-
charge by a constant-voltage source,
and is due to cyclical, ever-increasing
temperature and charging current.
One or more shorted cells or an exist-
ing high temperature and low charge
can produce the cyclical sequence of
events:
(1) excessive current,
(2) increased
temperature,
(3) decreased cell(s) resistance,
(4) further increased current, and
(5) further increased temperature.
This will not become a self-sustaining
thermal-chemical action if the con-
stant-voltage charging source is re-
moved before the battery temperature
is in excess of 160 °F.
(10) Pulsed-current battery chargers are
sometimes provided for NiCad batteries.
CAUTION: It is important to use the
proper charging procedures for bat-
teries under test and maintenance.
These charging regimes for recondi-
tioning and charging cycles are de-
fined by the aircraft manufacturer
and should be closely followed.
(2) Inspect battery terminals and quick-
disconnect plugs and pins for evidence of cor-
rosion, pitting, arcing, and burns. Clean as re-
quired.
(3) Inspect battery drain and vent lines
for restriction, deterioration, and security.
(4) Routine pre-flight and post-flight
inspection procedures should include observa-
tion for evidence of physical damage, loose
connections, and electrolyte loss.
11-20. ELECTROLYTE SPILLAGE.
Spillage or leakage of electrolyte may result in
serious corrosion of the nearby structure or
control elements as both sulfuric acid and po-
tassium hydroxide are actively corrosive.
Electrolyte may be spilled during ground
servicing, leaked when cell case rupture oc-
curs, or sprayed from cell vents due to exces-
sive charging rates. If the battery is not case
enclosed, properly treat structural parts near
the battery that may be affected by acid fumes.
Treat all case and drain surfaces, that have
been affected by electrolyte, with a solution of
sodium bicarbonate (for acid electrolyte) or
boric acid, vinegar, or a 3 percent solution of
acetic acid (for potassium hydroxide
electrolyte).
f. Shop-Level Maintenance Procedures.
Shop procedures must follow the manufac-
turer’s recommendations. Careful examination
of sealed batteries and proper reconditioning of
vented batteries will ensure the longest possi-
ble service life.
CAUTION: Serious burns will result
if the electrolyte comes in contact with
any part of the body. Use rubber
gloves, rubber apron, and protective
goggles when handling electrolyte. If
sulfuric acid is splashed on the body,
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