All 4000mah 'P' Packs are made up from 2 x 2000mah welgard cells in parallel, which come complete with gold connectors simply ‘daisy chain’, each pack together to add voltage. Charging can be done as either a complete pack at the flying field and during the week unplug the cells and charge each one separately to balance each pack. We recommend doing this between 5 to 8 cycles for longevity of the pack.