In a previous guide, we covered the basics of hybrid cars and how they work. Now, let’s take a closer look at the heart of a hybrid – the battery.
We’ll explore what’s inside, how it functions, and the types you’ll find in today’s hybrids.
What Is A Hybrid?
A hybrid vehicle combines gasoline and electric power to help move the car. Although hybrids still require gasoline, they generate electricity from wasted energy – such as heat from braking.
In hybrids, the electric motor mainly supports the engine during tasks like acceleration, rather than powering the car independently, as in electric vehicles (EVs).
Components of Hybrid Battery Pack
Hybrid vehicle battery packs are complex, highly engineered systems that enable electric and fuel power to work seamlessly together.
These battery packs are designed to store and supply high-voltage energy, supporting the vehicle’s electric motor during driving and recharging efficiently when braking.
To ensure safe, efficient, and reliable operation, each battery pack consists of several key internal and external components:
Components Inside the Battery Pack
Battery Cells and Modules:
The cells and modules are physically inside the battery pack, as they make up the core of the battery’s energy storage system.
Battery Management System (BMS):
Key parts of the BMS, such as voltage and current sensors, cell balancing circuits, and temperature sensors, are inside the pack to directly monitor the cells.
Some BMS control circuits may be housed outside the battery pack, especially in more modular setups.
Cooling System (Partially Inside):
Cooling Channels: In some designs, air or liquid cooling channels run through or around the battery pack.
Fans or Pumps: These components may be located either inside or just outside the pack, depending on the vehicle design.
Safety Components:
Relays, Fuses, and Disconnects: Often located within the pack, these components are crucial for safety.
Pressure Relief Valves: When present, these are typically part of the pack to vent gases directly from within.
Components Near (but Usually Outside) the Battery Pack
Inverter:
The inverter, which converts DC from the battery to AC for the electric motor, is typically outside the battery pack. It’s usually located nearby to minimize power loss.
DC-DC Converter:
This unit steps down the high voltage from the battery to lower voltage for the 12V battery and auxiliary electronics, and it’s usually located outside the battery pack, though often close by.
High-Voltage Cables and Insulation:
While high-voltage cables connect the battery to the rest of the vehicle’s electrical system, they run outside the pack and are insulated for safety.
How The Hybrid Battery Works (https://www.youtube.com/watch?v=q1KNKhGo4c0)
Now that the topic of understanding the core components has been covered, it’s fitting to see how these systems function in real time.
From the moment you power on the vehicle to the point it shuts down, the battery pack operates in a series of carefully managed steps. Below are the stages that occur for an average hybrid vehicle to perform:
Step 1: Battery Monitoring and Initialization
Battery Management System (BMS) Activation
As soon as the vehicle is powered on, the BMS begins monitoring the battery’s health and status. It checks voltage, temperature, and charge levels to ensure that the battery is ready for operation.
Initial Charge Check
The BMS checks the battery’s state of charge (SOC). If it’s within the optimal range (typically between 20-80%), the battery can supply power to the electric motor. If the charge is too low, the BMS signals the engine to begin charging the battery.
Step 2: Power Delivery to Electric Motor
Inverter Activation
When the electric motor is needed, the inverter converts the battery’s DC (direct current) power to AC (alternating current) power, which is what the electric motor requires to drive the wheels.
Electric Motor Powering
The electric motor receives this AC power and generates torque, which powers the vehicle, especially during low-speed driving or light acceleration.
Step 3: Energy Management and Recharging
Continuous SOC Monitoring
As the battery supplies power, the SOC decreases. The BMS monitors the SOC and adjusts power output as needed to avoid deep discharging, which can shorten the battery’s lifespan.
Regenerative Braking Activation
When you brake or decelerate, the BMS switches the electric motor to generator mode. The motor then captures kinetic energy from the wheels and converts it into electrical energy, which is sent back to the battery to recharge it.
Engine-Assisted Charging
If the battery’s SOC is low and regenerative braking alone isn’t sufficient, the system may activate the ICE. The ICE drives a generator to charge the battery or diverts some energy to keep the SOC within optimal levels.
Step 4: Temperature Regulation
Cooling System Engagement
As the battery gets used, it generates heat. The BMS continuously monitors temperature sensors within the battery pack. If the battery temperature exceeds safe thresholds, the cooling system (either air or liquid-cooled) activates to prevent overheating.
Thermal Management Adjustment
The cooling system operates dynamically, adjusting airflow or coolant flow based on how intensively the battery is being used and the ambient temperature. This thermal regulation prevents temperature-induced damage to the battery.
Step 5: Automatic Safety and Protection Mechanisms
Voltage and Current Regulation
The BMS ensures the battery operates within safe voltage and current limits to prevent overcharging, over-discharging, or excessive current flow. These protective measures extend the battery’s life and prevent electrical issues.
Isolation Monitoring
High-voltage batteries must be isolated for safety. The BMS continuously checks for any leaks or issues in insulation, shutting down the battery if any potential hazards are detected.
Step 6: Battery Standby or Shutdown
Transition to Standby Mode
When the vehicle comes to a stop or idles, the battery may enter a standby mode to conserve energy. If the SOC is high enough, it may temporarily power the vehicle’s accessories.
Shut Down Upon Vehicle Power Off
When you turn off the vehicle, the BMS shuts down the battery system, ensuring the battery enters a low-power state. This preserves battery health and conserves energy until the next time the vehicle is started.
Types Of Battery Available
Hybrid cars come in various designs, each offering its own pros and cons.
Overall, there are three types of batteries commonly used in hybrid cars: lead-acid, nickel-metal hydride, and lithium-ion batteries.
Lead-Acid
The oldest of the three, lead-acid batteries have powered electric cars for quite some time. They became a primary option for hybrid batteries due to their history in powering other automotive applications.
One main advantage of lead-acid batteries is their cost; they are the cheapest of the three types. However, they are also significantly heavier than their alternatives and far less efficient, while producing higher emissions.
Nickel-Metal Hydride (NiMH)
Nickel-metal hydride batteries have become the standard for hybrid vehicles over the last two decades. The first commercially successful hybrid also used NiMH batteries.
Compared to lead-acid batteries, they are much more efficient while maintaining a good battery life cycle. Unlike Li-ion batteries, NiMH batteries don’t require a complex cooling system to prevent overheating. However, they still suffer from being relatively heavy, similar to lead-acid batteries.
Lithium-ion (Li-ion)
Lithium-ion batteries are the next step in enhancing efficiency for hybrid cars, and for good reason. They offer a straightforward design while maintaining high energy storage capacity.
Compared to the other two options, they are also significantly lighter. However, the main drawback is their cost; lithium-ion batteries are the most expensive of the three, as they are still considered relatively new technology.
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