Foundations of Li-ion batteries, battery management systems

See how a battery management system monitors cell safety by processing pack voltage signals on a pcb, using dc-dc conversion and resistor dividers for accurate readings by a five-volt microcontroller.

Learn how a battery management system reads high pack voltage, filters and scales signals, and uses analog-to-digital converters to feed microcontroller firmware.

Describe how a microcontroller processes filtered and scaled signals from analog to digital conversion of cell and pack voltages, and uses communication and control blocks to alert and isolate faults.

Learn how nominal voltage defines a cell's voltage range and how capacity, maximum current, internal resistance, c-rate, and operating temperature from the datasheet shape lithium-ion cell selection and pack design.

outline the three lithium-ion form factors—cylindrical, prismatic, and pouch. cover the four internal constituents—anode, cathode, electrolyte, separator—and their intercalation during charging and discharging.

Explore the mechanical structure of a lithium-ion cell, including flat top and button top designs, the plastic casing, and how damage can cause short circuits and thermal runaway.

Learn to measure cell voltages with a multimeter, distinguish AC noise from DC, and see how voltage indicates state of charge and cell health in a Li-ion setup.

Discover how lithium ion cells charge, from the state of charge versus open circuit voltage curve to CC-CV charging, using a power supply and diode for safe current flow.

demonstrates charging a lithium-ion cell with a diode-protected power supply, showing a two-stage cc to cv process and a 2500 mAh capacity at 1/5 C.

Explore two-stage charging of a lithium-ion cell: constant-current up to about 4.1–4.2V, then constant-voltage with tapering current, highlighting c-rate, voltage polarization, and avoiding overcharge.

Explain the difference between constant current and constant voltage charging and why protection devices are needed. Demonstrate cc-cv switching around 4.1V using a compact board and safety practices.

Learn how power conditioning and filtering mitigate noise from high-voltage switching in EV subsystems, protecting sensors, op amps, and microcontrollers from voltage spikes and inaccurate readings.

Design filters to block noise pulses from reaching sensitive components in battery management systems, and explore basic filter components to understand their functions.

Explore how capacitive filtering uses a shunt capacitor to smooth a 1-volt signal and suppress 100kHz noise for a clean output.

Characterize noise profiles in ev systems, such as sinusoidal 100 khz, 20 khz pulses, and square waves. Measure with an oscilloscope or adc to guide filter design that blocks noise.

Explain how lithium-ion battery signal acquisition uses voltage, current, and temperature sensing with analog front ends and ADCs, then transmits digital data over ISO SPI to a microcontroller.

Explore the LTC 6811 chip pinouts and interfaces, including cell inputs, S1–S12 balance outputs, Vreg and ADC reference voltages, and the ISO SPI two-wire or four-wire configuration for a BMS.

Learn to read the LTC6811 reference schematic for voltage, current, and temperature signal acquisition in a BMS, and compare TI and Microchip alternatives.

Design clean BMS power rails by using dc-dc converters to convert high pack voltage to 5 and 3.3 v, ensuring stable current and proper load regulation for microcontrollers.

Examine isolation resistance's role in keeping high voltage safe in electric vehicles and appliances, preventing leakage to users and the chassis through contactors and isolators.

Explore voltage potential with a reference, using a floating metal plate to illustrate zero volts until tied to negative terminal, and resistance influences measurements in electric vehicle isolation.

Learn how to calculate isolation resistance between the high-voltage battery pack and the chassis in electric vehicles using fixed and switched resistances, voltage measurements, and a practical formula.

Learn how to measure isolation in electric vehicles by using the chassis as a reference, with the BMS monitoring HV isolation resistance to safety thresholds.

Understand the high voltage interlock loop (HVIL) and how the battery management system ensures safety during servicing by preventing main contactor engagement when faults are present.

Explore pre-charging in high-voltage ev systems, detailing resistor, inductor, and capacitor behavior, and explain how a pre-charge resistor and contactors safely raise the bus voltage before connecting the motor inverter.