Systems and methods are provided for charging a battery system of an Information Handling System (IHS) using a multimode AC adapter. Information reported by the multimode adapter is used to determine its capabilities, including whether it supports USB-PD transmission and also supports high-power transmissions of a voltage greater than the USB-PD voltages. The charge state of the battery system is monitored. When the battery is in a pre-charge state, the battery is charged using USB-PD transmissions negotiated with the multimode adapter. When the battery is in a bulk-charge state, the battery is charged using a high-power transmission negotiated with the multimode adapter. When the battery is in a top-off-charge state, the battery is charged using USB-PD transmissions negotiated with the multimode adapter. In light of the charging efficiency of a battery varying based on its charge level, the multimode adapter supports efficient charging at different charge levels.