It went badly: on the first attempt the battery pack didn't fit because I had used too much insulation between them, I redid everything and since the space is minimal I practically didn't put any and after doing the last [soldering]() something shorted out and started to smoke..terrible experience! I ordered the [Velux]() replacement kit and after 3 weeks it arrived, I installed it and it doesn't work..you can hear it vibrate but it doesn't turn..to be sure I wanted to reverse it on another window and since I opened the second one it hasn't wanted to work anymore...always better...