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A Method for Reviving and/orCommunicating with A Fully Discharged Smart Battery Pack

IP.com Disclosure Number: IPCOM000010230D
Original Publication Date: 2002-Nov-07
Included in the Prior Art Database: 2002-Nov-07
Document File: 6 page(s) / 78K

Publishing Venue

Motorola

Related People

Iilonga Thandiwe: AUTHOR

Abstract

Smart batteries for laptop computers and other host devices can, via several mechanisms, find themselves in a “dead state”. That is, a state where the pack voltage has dropped below some threshold such that the pack is completely non-functional. Not only can the pack not be used to power the host, additionally, it can’t be charged, revived, or interrogated. While there maybe valid reasons for certain cell chemistries to have a point of no return for charge it nevertheless is still valuable to be able to ask the pack how it died, what where its symptoms, what events preceded (or contributed) to its death, and in certain cases re-charge the pack. Currently there is no simple method to revive or interrogate a dead pack. This technique is a method for doing such without adding additional hardware or software to the battery pack, and avoids the need to open or disassemble the pack.

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A Method for Reviving and/or Communicating

with A Fully Discharged Smart Battery Pack

By Iilonga Thandiwe

3-23-00

Abstract

               Smart batteries for laptop computers and other host devices can, via several mechanisms, find themselves in a “dead state”.  That is, a state where the pack voltage has dropped below some threshold such that the pack is completely non-functional.  Not only can the pack not be used to power the host, additionally, it can’t be charged, revived, or interrogated.  While there maybe valid reasons for certain cell chemistries to have a point of no return for charge it nevertheless is still valuable to be able to ask the pack how it died, what where its symptoms, what events preceded (or contributed) to its death, and in certain cases re-charge the pack.  Currently there is no simple method to revive or interrogate a dead pack.  This technique is a method for doing such without adding additional hardware or software to the battery pack, and avoids the need to open or disassemble the pack.

Description of Method and Device

               Smart batteries for laptop computers are characterized by having a communications bus (e.g. SMBus, IIC, etc.) and a microcontroller or ASIC for communications, control, data processing, etc.  These batteries are typically capable of providing a wide variety of  information to the host unit and the user, including estimates of remaining run time, capacity, and operational history. The microcontroller is typically powered from a voltage regulator which is connected to the cells, while the communications bus is an open drain/open collector bus with pull-up resistors residing in the host.  The communications bus typically has a direct path from the external connectors to the micro and consequently requires devices (caps, zeners, diodes, etc.) to protect the micro from ESD events.  The typical circuit configuration is as shown in fig.1.  Diodes D1 and D2 are used to suppress ESD events on the bus.  D1 is used to capture positive transients, while D2 is for negative transients.  For effective protection the cathode of D1 is tied to the regulated supply bus Vdd.

               The voltage regulator U1, has as it’s input the cell voltage and its output drives the Vdd supply bus for the micro and other devices.  The U1 output additionally has a capacitor, C1 on its output for stability.

              

       
     
 

Fig. 1

 
 
 

U1 will typically only provide a regulated output down to a certain level after which it will no longer regulate, Vdd will drop below the minimum operating voltage of the micro, U2, and the micro will cease to function.  In this state the charge and discharge FETs default to the open condition.

               Once this state has occurred the only way to typically revive the micro for communication, is to restore the regulator input voltage (i.e. the cell voltage) up to the minimum level necessary for it to operate.  If the FETs are in the open state then it is not possible to simple attach a ch...