The manufacturer says swelling is normal if cells are not under compression. However, one should put these cells under compression as soon as possible. They must be compressed in a discharged state, preferably before the very first charging. Usually the cells come preconfigured as a pack of several cells with two end-plates and steel straps that press the plates together which provides sufficient compression. However, sometimes the cells are sold loose. In this case they can swell and the customer should design his own way of compressing them - for example with plates and studs or by mounting them into a strong box.