BTW, Attopilot is not available outside the US (it's actually not available at all, since Dean has run out of his first run of 100 and seems to not be making more until he switches to an IMU). Or did you actually mean ArduPilot?
The batteries you buy are for your aircraft, not Attopilot. The autopilot just gets its power from the RC system and that gets its power from the batteries that power the overall plane. If you're just getting into RC, I suggest you research a bit what airframe you want and then you can pick a battery.
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Are you thinking of how to power your aircraft??
If so, lipos are the way to go.