While working within a pre-set boundary wire, the self-charging robomowers monitor their battery levels and return to their charging stations when they're starting to run out of juice. With its 22.2 volt/1.8 Ah battery, the cheaper HRM 310 model is able to work a half-acre of lawn space for 30 minutes straight; the more expensive HRM 520 can work a 50 percent larger lawn twice as long, thanks to its 3.6 Ah battery. However, charging times also match the working times, so the 520 takes an hour to charge. The mowers are able to mow sloping lawns as steep as 25 degrees, and they both weigh around 26 pounds. Both have sensors that are able to monitor 360 degrees, and when the mower encounters an object it will back away.
There are three main cutting modes; Random, Directional or Mixed. Random is meant for dealing with large, open areas, and when encountering the boundary wire, the robomower will turn at a wide angle. Directional is for narrower lawns, enabling narrower maneuvers. Mixed is a mixture of the two, changing at regular intervals.
To keep the Miimo from being swiped from the owner's lawn while it's happily chugging away, it has an anti-theft mode that sounds an alarm when it's lifted off the ground. To resume operation, a security PIN code must be entered. The boundary wire will be installed by an authorized Miimo dealer, along with the docking station.