Bosch CompactTube 400 (NA) (BBP3247) The smart system. Slim integrated compact and delivering 400 watt hours at a weight of only around 2 kilograms its a real energy champion: The CompactTube 400 with innovative battery cell technology offers the highest energy density of all Bosch eBike batteries. This makes the extra-lightweight battery the ideal choice for sporty light eMTBs minimalist eGravel bikes or design-oriented eUrban bikes in short for anyone who loves the sleek appearance of conventional bikes but doesnt want to do without electric support.