BMS: Unbeatable Battery Power
To understand how a Battery Management System optimizes battery use, let us have a look at the current generation of electric cars where lithium-ion battery packs contain between 16 and 53 kilowatt-hours of energy. For a helpful comparison, a liter of premium gasoline provides 8.8 kilowatt-hours, so a lot is asked of the battery pack. It gets much-needed help from the Battery Management System. By controlling and monitoring each individual cell, the efficiency of the battery pack is optimized in the most precise way. Indeed, the BMS measures, monitors, and controls all relevant cell parameters, from cell voltage, current and temperature to operating processes. The BMS battery pack is constantly protected from complete charging or discharging; this has a positive effect on its service life and performance. The goal of a BMS in hybrid and electric vehicles is to achieve a battery life of 10 to 15 years while retaining more than 80 percent output capacity. To achieve this goal, any smart battery system needs reliable battery management that maximizes the range, reliability, and safety of the battery pack.
BMS: Getting Maximum Potential From Each Cell
It may surprise you to learn that a typical battery pack is operated in a limited State of Charge between 20 and 80 percent; only 60 percent of the capacity is used. The reason for this is safety - the limited capacity is intended primarily to protect the individual battery cells from over- or undervoltage. Small variations in cell characteristics and operating conditions can cause variations in self-discharges. A BMS can simultaneously ensure utmost safety and maximum capacity. The Battery Management System monitors each individual cell, which is why capacity can be maxed out to the operating limit without ever exceeding it. With lithium-ion batteries, this is a masterstroke because their discharge curve is incredibly flat over the operating range. The BMS must be able to detect even the smallest change in the State of Charge.
What is the Difference Between Passive and Active Cell Balancing?
Passive cell balancing is a simple and cost-effective solution in offline operations in which the cells with a high State of Charge (SoC) are discharged. However, this discharging involves the transformation of electrical energy into heat, a process which limits the balance to a maximum of 5% of cell capacity and hence takes a little time. In active cell balancing, electrical energy is transported between the cells both when discharging during operation and when charging. The BMS supplies the weakest cell with energy from the strongest and vice versa, depending on the charge status. The biggest advantage is that less heat is generated, the equalization current is optimized, and the timing is significantly shortened. The biggest challenge here is precision - the Battery Management System must detect deviations of less than ±10 mV to avoid measurement errors and be able to perform active cell balancing.
Better and Higher Battery Performance
We believe technology is the key to advanced, sustainable batteries. Our Battery Management System optimizes battery performance and drives forward our vision of sustainable and efficient use. As a partner, e.battery systems develops specific solutions based on years of experience and accumulated engineering knowledge. This includes electromobility components as well as individual prototyping, for specific requirements needs or for mass production. In projects all over the world, we have proven our competence as a partner for battery development.