Just to add to this, when I had my pack out to swap some cells I had it on a small wooden framed trolley I built with some 80mm castor wheels, and I was able to pull the battery pack up a small incline to my garage by myself with two ropes attached to the trolley. It wasn't easy but I very much doubt it weighs 253 killograms or I wouldn't have been able to move it up an incline on rough concrete at all.
Another thing I discovered on disassembly is that the majority of the battery "chassis" is not steel, but is either fibreglass or thick reinforced ABS plastic of some kind. The steel chassis is a relatively thin layer at the bottom underneath this fibreglass/plastic to support it.