Nuvation CEO Mike Worry is at Atmel’s EELive! 2014 ToT booth presenting a series of Tech Talks about his company’s EV Battery Management System. His presentations have been covered by a number of prominent journalists, including Steve Taranovich of EDN.
“We’e seen enough instances of battery disasters occurring over the last few years in our industry. Batteries have a tremendous amount of energy within and if not properly handled and charged/monitored can be dangerous,” writes Taranovich.
“With chemistries such as Lithium, each cell must have its voltage monitored and balanced. This not only extends battery life, but prevents tragedies. [This is why] Nuvation has expertly developed their customizable battery Management System (BMS) that can handle 10s to 1,000s of cells. The system is easily made compatible with lithium, nickel, silver based and other battery chemistries.”
In terms of the Tank Controller, Nuvation selected Atmel’s ATSAM4E8C, a 32-bit ARM Cortex-M4 controller to power a wide range of features, including Ethernet, UART, CAN, current shunt and optically-isolated GPIO.
As Taranovich notes, the Tank Controller is also equipped with an optically-isolated interface to battery pack management (PackMan) strings.
“The system handles soft-start, main start and emergency disconnect and controls the charging system to protect the battery,” says Taranovich.
Meanwhile, the PackMan, or BMS slave utilizes Atmel’s ATA6870N, a Li-Ion, NiMH battery measuring, charge balancing and power-supply circuit.
This IC is tasked with measuring all cell voltages simultaneously – and balancing cells with higher voltage. Each IC is capable of monitoring 6 cells, with a daisy chain configuration supporting up to 16 PackMan board or 96 stacked cells.
“Nuvation’s BMS must deal with the balance/imbalance of a battery pack. It looks at the state-of-charge (SOC) between cells in the pack,” Taranovich adds. “The usable SOC of pack is determined by the lowest energy cell and then the BMS has the task of balancing these cells accurately and quickly without overcharging or overheating the cell.”