Does the Ecovacs Winbot W2 only run when the battery is charged or does it also run via the power cable? I am asking because I have just bought the Ecovacs Winbot W2 Omni. On this model the battery only lasts for about 1 hour and it takes about 4 hours to recharge. It won't work without a full battery. That is far too little for me. My house has a lot of large windows. Cleaning all the windows means it takes me almost a week with the Omni.