T-34C AIRCRAFT SYSTEMS FAMILIARIZATION
The battery in the T-34C provides the emergency DC power source. It is a 24-volt, 24-ampere-
hour sealed valve regulated (SLA/VRLA) lead acid battery that is located in a compartment on
the right side of the fuselage forward of the canopy. Either the generator or the external power
unit recharges the battery.
The operating life of the battery will be affected by the battery charge, temperature of the
environment, and the electrical load. Charging and discharging of the battery produces two
undesirable elements, heat and hydrogen gas. Heat is removed through the battery compartment
vent system. Air enters the compartment through an air intake scoop in front of the windshield
and exits through an exhaust vent on the battery compartment door. The air from the air intake
scoop also enters a hose attached to the back of the battery case and flows through the battery
case vent system to remove the hydrogen gas. The air exits via a plastic hose which is attached
to the front of the battery case and extends out the bottom of the fuselage. The SLA/VRLA
battery is maintenance free and will not leak or spill in any attitude.
A two-position switch, labeled BATT, ON and OFF on the electrical control panel controls the
battery relay. Placing the switch to the ON position applies power directly to the essential and
power distribution buses. The switch must be on for engine starting, external power to enter the
system, and for the battery to be recharged.
Current operating procedure recommends the use of an external (ground) power unit on all starts
if available. The minimum voltage allowed for a battery start is 22 volts. A battery start below
22 volts is likely to cause overtemperature damage to the engine. Less than 22 volts requires use
of the external power unit. If the battery voltage is less than 18 volts, an external power relay
prevents external power from entering the DC system. This is a safety feature which prevents
overheating of the battery and possible explosion due to an excessively high charging rate. If
below 18 volts, the battery must be replaced before the engine can be started.
The generator is located on the accessory gearbox at the 12 o'clock position and is driven by the
accessory gearbox. Cooling air comes from the accessory air inlet duct through a hose connected
to the rear of the generator. The generator is the primary DC power source, and it is rated at 30
volts and 200 amps. The generator switch, located on the Electrical Control Panel, is labeled
position with momentary actuation to the ON and OFF positions. Momentary actuation to the
ON position closes the generator relay and applies power directly to the essential and power
distribution buses. Momentary actuation to OFF disconnects the generator from the buses.
ELECTRICAL POWER SYSTEMS 9-5