We often write about big battery pack deals here on Android Police: 10K, 15K, 20K, or as much juice as anyone could stick in these portable accessories. This deal is different. It's about a small 2000mAh battery that costs three Washingtons or less than a cup of Starbucks coffee.

But what good is 2000mAh really? It isn't enough to fully charge any modern smartphone even once so why bother with it? Well, this one measures 3.8 x 2.4 x 0.25 inches (9.65 x 6 x 0.63 cm) so it's small enough to fit in a pocket or the hidden zipper of a purse, and carry with you everywhere. You can use it to top off your phone when the battery's starting to run out by the end of the day or to quickly charge a bluetooth headset or other small accessory. It even has a built-in MicroUSB cable to make things easier so you don't have to hunt for one when you need to use it.

The battery has an MSRP of $14.99 though it has recently stabilized at around $6. It's now selling for $2.99 as an Add-On item, which means that you can't buy it alone but you can use it to top off another purchase. You can do worse if you're buying another $33 item and just want a couple of bucks to get free Amazon shipping.