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There are two values you need to be concerned about -> average current draw, and maximum current draw.Look at the datasheets of all the parts you plan on using, and sum up the current draw. Then select a battery capable of meeting both of those values.And its always best to round up, just in case you decide to add more stuff later in the future, or want to push the limits. ps - I split this topic, t'was entirely unrelated to the previous thread

Good question on the battery specs but the answer is not easy. So I'll give it a try.All batteries have what is known as internal resistance. This can be modeled as a resistor in series with the battery. An 'Ideal' battery has zero internal resistance has therefore has the ability to supply infinite current into a short circuit. It is this resistance that limits the maximum instantaneous current that can be drawn from a battery, the 2.2A for the AA batteries.

[...]I've noticed that most AA batteries have a maximum discharge rate of 2.2 Amps or so

With PWM, and a good choice of frequency, the current will be lower, as the induction of the motor will tend to integrate the voltage.

[...] "high-rate discharges of 2C", is that two times the battery capacity, or is it two Coloumbs?

I'm inquisitive as to the exact workings of your last sentence:QuoteWith PWM, and a good choice of frequency, the current will be lower, as the induction of the motor will tend to integrate the voltage.I'm a second year EE student, so I can begin to understand the implications of this, but not to the extent that I totally understand how it functions, could you possibly explain it a little?