Battery unit, battery module, and battery system

The present invention relates to a battery unit comprising one or more pairs of oppositely disposed receptacles, each said pair of receptacles defining a respective chamber for accommodating one or more cylindrical battery cells, each cylindrical battery cell having a first end adjacent a first end wall of a first one of said receptacles and a second end adjacent a second end wall of a second one of the pair of said receptacles. The invention further relates to a battery module comprising one or more battery units and to a battery system comprising a plurality of battery modules.