Specifications

Smart Battery Charger Specification
SBS Implementers Forum -Page 8- Revision 1.1
5. Smart Battery Charger Commands
The battery or the charger, depending upon the specific implementation may initiate communication
between the Smart Battery and Smart Battery Charger. In either case, the same minimum set of
information is transmitted between the battery and the charger. It is important to note that this
communication does not require host intervention and depending upon implementation, allows for
successful charging even when the system host is not powered or is absent.
Level 2 chargers are always slave devices and therefore all communication with these chargers is initiated
by the Smart Battery or other master device, typically the System Host. Whenever the Smart Battery's
BatteryMode() CHARGER_MODE bit is cleared (default) and the Smart Battery desires to be charged and
detects the presence of a Smart Battery Charger (optional), it will send the ChargingCurrent() and
ChargingVoltage() values to the Smart Battery Charger. The Smart Battery will continue broadcasting
BOTH of these values an interval of not less than 5 seconds nor greater than 1 minute in order to maintain
correct charging. For example, the Smart Battery may detect the presence of a Smart Battery Charger by
recognizing a charge current or voltage at the battery terminals and begin regular broadcasts to the charger.
Even if no Smart Battery Charger is present, the Smart Battery may choose to broadcast to the charger
address. See Smart Battery Data Specification for details (refer to the References section).
Level 3 Smart Battery Chargers may initiate charging by interrogating the Smart Battery for
ChargingCurrent() and/or ChargingVoltage(). For example, this may be initiated by the presence of a
charge source, such as an A-C wall adapter, or by direct command of the system host. Further, Level 3
Smart Battery Chargers must also operate as slave devices in the same manner as Level 2 chargers.
Whenever the Smart Battery detects a critical condition, it will become a bus master and send an
AlarmWarning() message to both the Smart Battery Charger and the System Host, as appropriate, to notify
them of the critical condition. The message sent by the AlarmWarning() function is similar to the message
returned by the BatteryStatus() function. All Smart Battery Chargers must discontinue charging upon
receipt of an AlarmWarning() message if the error indicates that charging should be terminated. See the
description of the AlarmWarning() function for a list of the alarms that should terminate charging.
The following functions are used by the Smart Battery Charger system to communicate with a System
Host, Smart Battery and other devices connected via the SMBus. All functions include a command and
then either read or write a 2-byte word. For more details about the data structure and communication
protocol, see the System Management Bus Specification (refer to the References section).
The default mode of the Smart Battery Charger described by this specification does not use the
voltage and current scaling information contained in the Smart Battery’s SpecificationInfo(). The
charger interprets all voltage and current commands using one as the scaling factor. A Level 3
charger is allowed to use the battery’s scaling information in a non-default mode.