I got one of these as a present for a friend. It worked and then when I went to wrap it up a few days later, it didn't work and had a rattling noise. Given the cost of returning it and that we were on our way to this friend's house, my husband decided to take it apart to see if he could repair it. The rattling was the remains of one battery, which must have swollen and come apart, leaving bits of brittle material inside the ball. He replaced all three batteries and had to do quite a bit of resoldering as the build quality was so poor - and one of the wires to the front contacts was held on by one strand and had to be rejoined. He got it working with 3 new batteries but one of the four little magnetic discs fell off the front of the ball and had to be glued back in with superglue.
Result, a working product which should continue to work for some time. But I'm really, really unimpressed by this. Don't buy this.