it just says this on the dell site
Your gaming mouse has an embedded rechargeable battery. The battery life is approximately 3.5 hrs.
For best results, ensure that the battery is fully charged for the first time usage.
Hi, I got this mouse with rewards and love the feel, but hate the administration. I have no way of knowing what the power level is at any time (command center, if it shows a value, stays on that value until the battery drains, which is effectively like not showing a number at all). The only way I know the battery is low is if windows creates a notification. Also, the battery seems to be draining rather quickly, though I haven't been worrying about turning the mouse on/off.