Battery vs Alternator

[Macgyver]

Hey guys,

I was speaking to some people today and I got some conflicting opinions. I'm hoping you guys can clarify!

1. Some people argued that the aircraft's electrical systems are powered directly by the battery, while the alternator is simply there to reenergize the battery and to prevent it from dying.

2. Others argued that the battery is only used during starting and as a back-up power source. The alternator(s) are driven by the engines and they produce and directly supply the electrical systems with their energy.

Comments?

[vapilot2004]

In a general aviation aircraft (28V DC) once the engine is running and the alternator brought on line it takes over the battery load (literally - outputs a higher voltage) and provides all of the power for aircraft systems while charging the battery too. So I would say the folks that posit no 2 are better informed on this.

In larger aircraft, generators are used to supply AC current to a majority of systems, while TR units charge the main battery and supply power to all of the DC systems.

Oh, and MG, I thought you knew all about this stuff :)

[Macgyver]

Oh, and MG, I thought you knew all about this stuff :)

Thanks for the response Va. I guess my old age is catching up with me ;)