Final answer:
Commercial aircraft typically use 24-volt systems, with smaller aircraft sometimes using 12-volt systems. The voltage requirement depends on the design and electrical system demands of the aircraft. Semi-tractor trucks connect batteries in series for starting engines and in parallel for normal electrical operations.
Step-by-step explanation:
The minimum voltage for flight in aircraft batteries largely depends on the aircraft's design and the voltage required by its electrical systems. In general, commercial and large aircraft use 24-volt or 28-volt systems. Smaller aircraft may use 12-volt systems, similar to car batteries. However, more advanced or larger aircraft might require 24 volts or even higher voltage systems for optimal performance. It's essential for aircraft to have a reliable electrical power source, as it powers critical systems like communications, navigation, and, in some cases, flight systems.
Regarding battery connections, batteries can be connected in series to increase voltage output, which is beneficial for heavy loads like starting the engine of a semi-tractor truck. Connecting batteries in parallel increases the current capacity or Ampere-hours (Ah), which can provide a longer power supply duration for the electrical components that operate on 12 V. Each battery configuration serves its purpose based on the power requirements of the vehicle or device it's used in.
For semi-tractor trucks that require 24 volts for starting the engine, two pairs of 12-V batteries could be connected in series to give 24 V each and then connect those pairs in parallel to maintain the voltage at 24 V but increase the capacity. For normal operation requiring 12 V, all four batteries could be connected in parallel. The 24 V is preferred for starting the engine because it provides a higher starting torque, which is necessary for a heavy load like a semi-tractor truck's engine.