Battery Technology Study Notes: Electrical & Electronics Foundations for Packs, Chargers, and BMS

Electric charge

The amount of electricity carried by electrons/ions.

Current

The rate at which charge flows, calculated as $I = \frac{Q}{t}$.

Capacity (in batteries)

The maximum charge a battery can deliver, commonly expressed in ampere-hours (Ah).

Ampere-hour (Ah)

A unit of electrical charge representing the charge transferred by a steady current of one ampere for one hour.

C-rate

A measure that normalizes current by capacity, indicating how fast a battery can be charged or discharged relative to its capacity.

Voltage

The electrical push driving current through a circuit, expressed as $V = \frac{W}{Q}$.

Open-circuit voltage (OCV)

The voltage across the terminals of a battery when no load is connected.

Loaded voltage

The voltage across the terminals of a battery while supplying or absorbing current.

Nominal voltage

A convenient mid-range voltage value used for labeling battery packs.

Resistance

A measure of how strongly a component opposes current, calculated as $R = \frac{V}{I}$.

Internal resistance

The resistance within a battery that causes voltage drop and heating during operation.

Power

The rate of energy transfer, calculated as $P = VI$.

Energy

The total amount of work done, calculated as $E = Pt$.

Watt-hour (Wh)

A unit of energy equivalent to one watt of power used for one hour.

Terminal voltage under load

The voltage of the battery when current is flowing and affected by internal resistance.

Kirchhoff’s Current Law (KCL)

The principle that the sum of currents entering a junction equals the sum of currents leaving.

Kirchhoff’s Voltage Law (KVL)

The principle that the sum of the voltages around any closed loop in a circuit must equal zero.

Buck converter

A type of DC-DC converter that steps down voltage while increasing current.

Boost converter

A type of DC-DC converter that steps up voltage while decreasing current.

Switching losses

Energy wasted during the transition of a switch in a power conversion, affecting efficiency.

Linear regulator

A device that maintains a constant output voltage by dissipating excess voltage as heat.

Constant Current (CC) mode

A charging method where current is regulated to a set value during charging.

Constant Voltage (CV) mode

A charging method where voltage is regulated to a set value after reaching charging limits.

Battery Management System (BMS)

A system that monitors battery conditions, manages charging, and ensures safety.

Resistance in ohms (Ω)

The unit of measurement for resistance, defined as $R = \frac{V}{I}$.

Current shunt

A precision resistor used to measure current by observing the voltage drop across it.

Thermistor

A temperature-dependent resistor used in battery systems for thermal monitoring.

Diode

A semiconductor device that allows current to flow in one direction and blocks it in the other.

MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor)

A voltage-controlled semiconductor device widely used for switching and amplifying electronic signals.

R_DS(on)

The resistance in ohms when a MOSFET is fully turned on.

Efficiency in converters

The ratio of output power to input power, often expressed as a percentage.

Voltage sag

The temporary reduction in voltage experienced during heavy load conditions.

Precharge circuit

A system designed to limit inrush currents when connecting to a load by initially charging capacitors.

Backfeed protection

Methods to prevent unintended current flow back into circuits, often using isolation diodes.

Voltage divider

A circuit that reduces voltage to a desired level via two series resistors.

Filtering in circuits

The process of removing high-frequency noise from signals, often using RC (resistor-capacitor) filters.

Hysteresis in control systems

A method that prevents rapid toggling of a system by using different thresholds for turning on and off.

Overcurrent protection

Safety mechanisms that disconnect a circuit in the event of excessive current flow.

Reverse polarity protection

Methods to prevent damage from incorrect connections of power supply terminals.

Isolation in battery systems

The design consideration of keeping different parts of a battery system electrically separate for safety.

Charging termination conditions

Criteria for stopping the charging process, such as voltage limits or current drop.

C-rate to current conversion

The method used to calculate the current based on the capacity of the battery and the specified C-rate.

Ohm's law

The fundamental relationship between voltage, current, and resistance, given by $V = IR$.