ZDNET's Lab Awards series combines the rigorous testing done in our Louisville, Kentucky-based lab and our decades of hands-on testing expertise. Our lab has tested everything from robot vacuums to phones to VPNs -- in each product category, we award a winner that outperforms the others in a given test, like battery life.Also: Prime Day ends soon: We hand-picked the 95+ best deals still live, before they disappearMany of the products we've tested in the lab are flagship devices from big-name brands, so they don't come cheap. But during Amazon's Prime Day sales event, a few of our Lab Award winners are on sale, so you can save on the best of the best. The best Lab Award winner deals for Prime Day The M5 iPad Pro won our very first lab award for longest battery life in a tablet. In our testing, this iPad lasted a little over 15 hours at maximum brightness before needing to be charged.Also: We ran battery tests on 9 popular tablets - this model lasted the longest (and other surprise results)We tested each tablet's battery life a total of 12 times: three times with maximum brightness/audio, three times with minimum brightness/audio, three times with maximum brightness/audio on Airplane Mode, and three times on minimum brightness/audio on Airplane Mode.