As a tech geek I have 3 times the amount of USB power banks than what I'll ever use. I like to keep one in every car and the Model 3 is no exception. IMG_7797 by Lanzer posted May 30, 2018 at 2:19 AM My recent purchase is a 15Ah power bank that has a built in solar panel to keep the batteries topped off. I've been looking for a good place to store the power bank so it can charge without it being too unsightly, and then I found the trunk grill. I had no idea why there is a grill above the trunk, then I realized that the subwoofer is installed in the trunk. No wonder the Model 3 had such good bass! IMG_7798 by Lanzer posted May 30, 2018 at 2:19 AM Just slip the power bank in IMG_7799 by Lanzer posted May 30, 2018 at 2:19 AM And it only goes in so far. It blocks off a small portion of the grill and it doesn't seem to affect the sub woofer's performance. I hope that the solar panel still receive enough power behind the grill. Time will tell! PS - the power bank is by RavPower. It sells on Amazon for about 26 bucks.