There’s no reason to charge just your device when you could also give your batteries some extra juice. The OtterBox OtterSpot Wireless Charging Base agrees, which is why it lets you stack wireless batteries for charging. With a 36-watt base, this Qi charging station can power up to three OtterSpot batteries at once. This is in addition to your smartphone charging at the same time. So if you’re getting ready to head out for an off-the-grid weekend where you need..