Amazon offers its Amazon Prime members the Eneloop 1500 Ni-MH Pre-Charged Rechargeable AA Battery 8-Pack, model no. SEC-HR3U8BPN, for $19.25 with free shipping. (Non-members can spend over $25 to qualify for free shipping; otherwise, shipping adds $5.58.) That's $2.41 per battery and the lowest total price we could find by $6. These 1,500 mAH AA batteries are precharged and can be recharged up to 1,500 times.

Amazon Prime membership is $79 per year; however, Prime is free for college students for one year, and free for parents and caregivers for three months.