This illustration shows a typical arrangement of the different components for a battery pack in a portable system. For a multi-cell Lithium-Ion pack, it is important to monitor each individual cell within the pack. As shown in later sections, keeping the cells in a multi-cell pack in a matched or “balanced” condition is essential. The charging IC is typically external to the pack, and regulates the current and voltage from an external DC source to the precise levels required for a Lithium Battery. External power conversion circuits translate the variable voltage from the battery into the specific regulated levels required by different sub-circuits in the electronic device. For medium and larger-sized battery packs, it may also be recommended to implement a second safety circuit as a backup in case the main safety circuit malfunctions.  In case of a fault condition, the primary safety circuit can disconnect the battery from the external circuit, and reset the protection when the fault condition is removed. The secondary protection circuit typically blows a fuse when a fault condition is seen because by that point, the primary circuit has already failed and the pack should be removed from service.