New Year repair job. Years ago we bought a cordless vacuum (Ergorapido, by Electrolux) that has recently been lasting only a couple of minutes on a charge. The battery pack isn't modular, but with some scratching around online I found the battery set with wiring harness from a Chinese supplier, which I assume are output from the same factory that produces them for Electrolux. Took some doing, but the new batteries have been squeezed into the case, and it all seems to work.