Japan’s Denso Corporation has come out with a new battery monitoring unit for lithium-ion batteries used in electric vehicles that they say is simpler and cheaper to produce than voltage control devices used in laptop computers and other hardware.
The unit is already installed in the Toyota Prius plug-in hybrid, which launched late 2009.
In general, a battery monitoring unit detects a battery's voltage, current, temperature and other parameters. Energy-dense lithium-ion batteries consist of multiple cells, with fluctuating voltages that must be controlled cell by cell.
The conventional voltage control method for these batteries converts analogue voltage data from each cell into the digital form. Then, using an arithmetic circuit, the data is processed to detect if a cell is operating at a higher voltage, and in such cases made to discharge.
Denso says its new method operates by detecting the average voltage of all the cells. Using a simple logic, it detects if any cell is operating at a voltage higher than this average, and in such an event, causes it to discharge. This method operates at the same level as the conventional method, the supplier says.
The company claims that the new method performs at the same level as the conventional one, but with a more simple structure that does not need high-performance analog-digital conversion circuits or arithmetic circuits.
Since 1997, when Toyota first launched Prius, DENSO has been providing the automaker with energy-saving technologies. One of their most recent innovations, the world's first passenger vehicle air conditioning system that uses ejector technology, is installed on the new 2010 Prius. The ejector, which is a small refrigerant injector, contributes to an overall reduction in power consumption by up to about 25 percent, compared to conventional air conditioning systems and is part of the reason for the 2010 Prius’ increased efficiency.
Denso is based in Kariya, Aichi prefecture. Listed on the Tokyo, Osaka and Nagoya stock exchanges, the company recorded consolidated global sales totalling $32 billion for the fiscal year ending March 31, 2009.