Each cell establishes the common-mode level for the measurement input from the one above it. It is beyond the scope of this article to discuss these products in any depth, but it is worth noting how such devices communicate in a stack configuration.
#Sure power battery isolator series
Currently, two application-specific special-purpose (ASSP) products are available from Analog Devices for cell monitoring: the AD7280, intended for use as a primary monitor, is based on a high-speed multiplexed 12-bit analog-to-digital converter another device, intended for use as a backup, or redundancy monitor, is based on a series of window comparators. Figure 1 shows a common approach to building and monitoring an HV stack.Ĭell-monitor ICs typically handle six or 12 cells. The electronics for monitoring a NiMH stack are thus considerably simpler than those for a Li-Ion stack. It is not generally necessary to measure the temperature of each Li-Ion cell, but the facility to do so should be available. With stacks based upon lithium-ion (Li-Ion) chemistry, however, it will be necessary to monitor the voltage of each cell to detect an over- or undervoltage condition on any individual cell in the string. For instance, the behavior of HV stacks based upon nickel-metal hydride (NiMH) chemistry is very well understood, and generally no effort is made to measure individual cell voltages it is sufficient to measure the total voltage of all the cells within a particular pack. Whether it is essential to monitor the voltage of each cell depends on the cell chemistry. The cell-monitoring integrated circuits associated with the cells are physically close to the monitored cells and are powered by the cells themselves. Packs containing large numbers of cells are physically larger and more awkward to fit into typical vehicle spaces. The original equipment manufacturer generally specifies the physical packing of the cells into enclosures called packs, which typically contain from six to 24 cells in series. Thus, the communications method must be safe and reliable. Although these stacks are inherently dangerous, they must still communicate with the cell monitoring electronics, which are usually located within the battery enclosure.
Since it is generally accepted that more than 50 V or 60 V can prove lethal to human beings, and even lower voltages can damage electronic equipment-considering the stability concerns about cells using some types of electrochemical reactions-safety is a key concern. Although we discuss here the use of battery stacks in vehicles, the underlying issues are common to all types of stacks.īattery stacks for transportation can typically involve 100 or more cells, providing hundreds of volts.
HV stacks are already used in many industries and applications outside of the transportation industry-typically in uninterruptible power supplies (UPS) to store energy from the grid in dc form as emergency dc supplies in 48-V communications equipment as emergency supplies in crane and lift systems and in wind turbines for feathering the blades in an emergency. EVs must be plugged into a power source for charging some newer hybrids are designed as plug-in hybrid electric vehicles (PHEV), which are considered to be essentially EVs with an ICE for range extension. Such high-voltage (HV) stacks are used in all-electric vehicles (EV)-as well as hybrid electric vehicles (HEV), which rely on an internal-combustion engine (ICE) for charging and (in many cases) shared propulsion. These “green” vehicles rely on batteries of series-connected cells to obtain sufficiently high voltage to operate the motor efficiently. Isolation in High-Voltage Battery Monitoring for Transportation ApplicationsĬars with wheels driven by battery-powered electric motors, continuously or intermittently, have become a hot topic.
0 kommentar(er)
