Q: What kind of rechargeable AA batteries can I use?
A: We recommend name-brand, Nickel-Metal Hydride (NiMH), at 2300mAh
'mAh' is essentially the size of the battery's "gas tank." Our earlier documentation recommended 2500mAh NiMH, but now we know better. If you go above 2300mAh, you are likely to run into quality issues with your batteries. If you go too much lower than that, then you are going to get fewer doses, so there's a fine range. This is not to say that Joe-Bob's 2-billion mAh battery won't work perfectly, but it's a cash risk.
You may also use Sanyo Eneloop batteries of any mAh --those batteries are awesome.