of leg 1121 the supported portion can be at a surface of leg 1121 within it and so on of course while only a single battery wire 1146 is being described this is only for the purpose of simplicity another battery wire not shown may accommodate the second electrical pole of the cell of battery block 1161 i e the opposite polarity or complementary polarity or reference voltage of the cell in some embodiments battery wire 1146 may have a flexible portion an example is now described fig1 is a partly conceptual diagram of sample components of a cpr system made according to embodiments and in a larger scale than those in fig1 so as to show a possible detail according to an embodiment in fig1 components include a central member 1241 to which a motor 1249 is attached leg 1221 is coupled to central member 1241 by using a joint 1281 accordingly leg 1221 can be rotated with respect to central member 1241 around joint 1281 a battery wire 1246 has a first end 1291 that is electrically coupled to motor 1249 and has a supported portion that is supported by leg 1221 at a point 1224 battery wire 1246 includes a flexible portion 1293 between first end 1291 and point 1224 flexible portion 1293 is distinct from the supported portion and is supported by neither central member 1241 nor leg 1221 accordingly flexible portion 1293 may flex as leg 1221 is rotated with respect to central member 1241 as already mentioned with reference to fig1 battery block 1161 can be configured to be supported by any component of retention structure 1140 of course as before the battery block has a battery housing and a cell within the battery housing.