Energizer Power Charger are on sale for $7.99, plus you’ll get 1,000 in Walgreens Balance Reward Points.  There is also a $3.00/1 Energizer Walgreens Mobile Coupon.

Buy 2 Energizer Power Charger $15.98
Use $3.00/1 Energizer Mobile Coupon (takes off $6.00)
Use 2 $1.00/1 Energizer Batteries, Flashlight, or USB Wall or Car Charger, SS 12/9 (exp. 1/5/13)
Pay $7.98, Get 1,000 Balance Rewards
Total: $6.98 or $3.49 each after coupons and BR Deposit