Amazon's decision to design its second-generation Amazon Echo smart speaker with a removable sleeve makes the device customizable. But there's a hidden feature I wasn't aware of until I installed Ninety7's Sky Tote Portable Battery Base: a set of electrical contacts tucked behind a rubber plug on the bottom of the speaker. These contacts enable the Echo 2 to draw power directly from the Sky Tote's large battery, which is charged in turn by the AC adapter that comes with the Echo 2. Operating your Echo 2 on battery power allows you to take the smart speaker with you into any room in your home or even into the yard if your Wi-Fi network is strong enough to reach there. That's a much less expensive alternative to putting an Echo in every room for smart home control, or investing in a multi-room audio system so you can listen to music everywhere. You can also take a battery-powered Echo 2 on picnics and camping trips if you create a mobile hotspot with your smartphone.

Ninety7 specializes in battery docks that render smart speakers portable, so it's appropriate that the company's new product for the Amazon Echo 2 features a large, easy-to-grab handle. The Sky is a replacement sleeve for the Echo 2 that docks the speaker to an 8800mAh Li-ion battery, so you can take Alexa out in the yard or on even on the road. The company says the battery should power an Echo 2 for about 8 hours, and a column of four LEDs near the bottom of the sleeve report the battery life remaining. I'm sure that will vary depending on how many times you summon Alexa and how much you use the Echo 2 to stream music. The battery gets recharged from the Echo 2's factory AC adapter and cable.

In the land of smart home appliances, Amazon has been tops for years. And after spending time with the company's new Amazon Echo, I have no reason to believe that's changing anytime soon. Over the last couple of weeks, I've been using the new Amazon Echo (2nd generation), an update to the company's wildly popular smart home appliance. And after putting it through its paces, adding skills, testing its microphone, and seeing how well its speaker could blast music around the house, I'm more convinced than ever that Amazon AMZN knows how to build a smart home device. Get Data Sheet, Fortune's technology newsletter And when the second-generation Echo launches on Tuesday for an affordable $100, I think many shoppers will discover the same.