Smart batteries

Technologically it is important that smart battery packages, featuring power management by electronic devices within the battery package, are becoming a necessity due to the sensitive charging characteristics of Li and Ni-MeHy batteries, it should be noted that the same principles at a fraction of the cost have been successfully applied realized by simple reversal protection and overflow components by the low-cost RAM batteries. 

Another useful calculation is the remaining operating time until a battery is empty. A simple estimate can be calculated using the remaining capacity of the battery (derived from SOC and last full capacity) divided by the present discharge current. More advanced calculations can use an average or predictive discharge current or compensate for temperature, just to list a few examples. The typical calculated data values commonly used in laptop computers was standardized in the Smart Battery Data Specification, Revision 1.1, published in 1998 [12]. 

Smart Battery Data Specification, Revision 1.1, System management Implementer s Forum, Copyright 1998, www.smbus.org/ www.pmbus.org/. 

ELECTRONIC ENERGY MANAGEMENT AND DISPLAY— "SMART" BATTERIES... 

During the past decade, an important development in rechargeable battery technology has been the introduction of the use of electronic microprocessors to optimize the performance of the battery, control charge and discharge, enhance safety and provide the user with information on the condition of the battery. The microprocessor can be incorporated into the battery (the so-called smart battery), into the battery charger, or into the host battery-using equipment. 

In order to ensure effective communication between the battery and host device, standard methods of communication are required. One method developed by battery manufacturers and microprocessor companies is the Smart Battery System (SBS) based on the System Management Bus. In 1995, the Smart Battery Data Specification was released by the SBS Forum. These specifications detail the communications method, protocols and the data interfaces between various devices. These specifications are periodically updated and available on the forum website, www.sbs-forum.org. 

One possible Smart Battery model is a system consisting of a battery, battery charger and a host (notebook computer, video camera, cellular phone, or other portable electronic equipment) as illustrated in Figure 5.18. 

FIGURE 5.18 Outline of a Smart Battery System (from Reference 7). 

The Smart Battery consists of a collection of cells or single-cell batteries and is equipped with specialized hardware that provides present state, calculated and predicted information to its SMBus Host. These may monitor particular environmental parameters in order to calculate the required data values. The electronics need not be inside the Smart Battery if the battery is not removable from the device. 

The Smart Battery communicates with the other devices (such as the SM (System Management) Bus Host and the Smart Battery Charger) via two separate communication interfaces ... 

The first uses the SMBus CLOCK and DATA lines and is the primary communication channel between the Smart Battery and other SMBus devices. The Smart Battery will provide data when requested, send charging information to the Stuart Battery Charger, and broadcast critical alarm information when parameters (measured or calculated) exceed predetermined limits within the particular Smart Battery. 

The other required communication interface is the secondary signaling mechanism or Safety Signal on a Smart Battery pack connector. This is a variable resistance output from the Smart Battery which indicates when charging is permitted. It is meant as an alternate signaling method should the SMBus become inoperable. It is primarily used by the Smart Battery Charger to confirm correct charging. 

The Smart Battery Charger will also receive critical events from the Smart Battery when it detects a problem. These include alarms for charging conditions or temperature conditions which exceed the limits set within the particular Stuart Battery. 

The SM Bus is a specific implementation of a PC-bus that describes data protocols, device addresses and additional electrical requirements that is designed to physically transport commands and information between the components of the Smart Battery system. 

The SMBus Host represents a piece of electronic equipment that is powered by a Smart Battery and that can communicate with the Smart Battery. The SMBus Host requests information from the battery and then uses it in the systems power management scheme and/or uses it to provide the user information about the battery s state and capabilities. The SMBus Host will also receive critical events from the Smart Battery when it detects a problem. In addition to the alarms sent to the Smart Battery Charger, it receives alarms for end of discharge, remaining capacity below the user set threshold value and remaining run time below file user set threshold value. 

Figure 5.19 is a schematic block diagram of a Smart Battery system, in this case for a three cell Lithium-Ion battery. 

V. Diori, and C. Martinez, Smart Battery Chips Maximize Usable Battery Capacity and Battery Life, Battery Power Products and Technology, April 1999. 

Another approach is the smart battery. These batteries incorporate features ... 

J. Norman Allen, The Payoff in Smart Battery Electronics Battery Power Products Technology, July 2000. 

These conditions caused a move toward standardization of smart batteries. Critics objected because they desired to use a unique power management scheme. Manufacturers of battery packs were concerned that the standards would limit them to form factors that would limit their... 

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