Hi,
I'm just an aircraft mechanic so I'm not an expert.
APUs, in general, have a DC starter which demands a lot of energy in the APU start, this is why APUs have their own batteries and they are normally bigger and heavier than others (more cells).
Is it an answer to your question?
Sorry my english is not very good.
Last edited by barrel; 21st July 2012 at 08:56.