Hybrid Car Battery Lifespan Explained – Answers to Common Questions

Hybrid cars are all the rage these days. The world’s population is growing and there are many growing economies. This means that there are now more cars than ever on the road. More cars means more pollution. You just need to look at countries in South East Asia where smog is quite common as a result of heavy industrial and vehicle pollution. Hence, there is now enormous pressure on the government and car manufacturers around the world to increase the fuel efficiency of cars and hence drive down pollution.  

More and more car manufacturers are looking into novel technologies such as hybrid and electric vehicle technology. They are producing more hybrid vehicles from scratch or converting their regular car models into hybrid models.

Improving Fuel Economy in a World Battling Climate Change

Car engines generally are not very efficient. Most of the energy is lost in the form of heat and also because it is scientifically impossible for them to exceed a certain level of thermal efficiency. Cars generally use up a lot of energy in overcoming frictional forces such as air resistance. More energy will be wasted on air resistance if the shape of the body has sharp edges and contours.

So, one way that car manufacturers try to improve fuel efficiency is by focusing on optimizing the aerodynamic shape of car bodies.  The best way to do is to streamline the car body as much as possible. You would have noticed how the bodies of fish have a smooth, elongated shape. This applies the same concept. Streamlined shapes overcome resistance from fluids such as air or water more easily. Of course, there is only so much car manufacturers can do. Slight changes in the car body shape due to added cargo, for example, can significantly affect air resistance and hence fuel economy.

Other technologies to improve fuel economies have included things like improved fuel injectors, continuously variable transmission (CVT) that helps to run the engine at its optimum speed, systems to extract and reuse waste heat from the exhaust, lighter construction materials to lower the weight, and finally hybrid technologies also improve fuel economy.

Hybrid Vehicles

Hybrid Electric Vehicles (HEVs) uses regular internal combustion engines in conjunction with an electric battery that powers an electric motor. They essentially have two sources of power for the car: petrol or diesel and electric power.

Popular car manufacturers have started to offer hybrid options. Examples include Hyundai’s Ioniq series (which was recently named the most fuel-efficient car in the US) and the Toyota Prius which is a full hybrid.

To understand how hybrid batteries work, it is important to have a basic understanding of their components and the different types available.

There are several types of hybrid vehicles:

Series Hybrid

These types of hybrids do not directly use the gasoline engine to drive the car. The engine instead runs the electric motor. The electric motor is normally run by the generator or battery pack. The car’s control system will decide on the amount of power that should be dedicated and where it comes from (generator, battery or engine).

Parallel Hybrid

These types of hybrids drive the car using both the internal combustion engine and the electric motor. The basic power is sourced from the electric motor while the engine is engaged when power requirements are much higher. So, when the vehicle is in idle, the engine can be switched off. The battery is mostly charged by regenerative braking.

These are the most commonly available, simplest, and cheapest hybrid type in the market.

Plug-in Hybrid

These types of hybrids rely more on electric power for running the car. They have larger batteries than cars. They can cover a greater distance relying just on electric power than other hybrids.

What is unique about these types is that the batteries are charged in public charging docks, similar to gas stations.

Full Hybrids

With these hybrid vehicles, the car fully relies on electric power from the motor to drive the car. So, the motors and batteries are quite powerful. They are also the most efficient of all hybrid vehicles. With full hybrids, you can choose from parallel, series or full-electric modes.  

In addition to the regular internal combustion engines, the core components of a hybrid include:

Electric Motor

Hybrid cars mostly rely on gasoline like normal cars, but they also have electric power that acts as a supplement to the gasoline. The electric motor helps to run at speeds that the internal combustion engine is not very efficient at. The additional power source also means that hybrid vehicles can use smaller internal combustion engines and they have a higher fuel economy than regular cars.  

Automatic Start-Stop Technology

This feature ensures that no fuel is wasted when the vehicle is in idle, such as during traffic. It turns off the engine and automatically restarts it when the accelerator is pressed, or brake is released. The process is very smooth and aims to increase the fuel economy.

Regenerative Braking

Normally when a car decelerates, the momentum is lost in the form of heat. Regenerative braking is a system where it absorbs this energy which would otherwise be lost and reuses it elsewhere. The movement of the wheels drive the electric motor which temporarily acts like a generator.

Rechargeable Electric Battery

Hybrid vehicles have a ‘battery pack’ that can be recharged to provide and store electric power from the motor. The battery pack is comprised of separate battery cells that form one unit. Hybrid car batteries are continuously improving to improve efficiency and to save weight and space (since batteries taking up weight and space is a common complaint about electric and hybrid vehicles).

The most common types of hybrid car batteries include lithium-ion, lead-acid and nickel-metal hydride.

How Hybrid Batteries Work

It is important to note that hybrid cars also have normal 12 V car batteries. Hybrid batteries are there to power up the electric motor. They are charged by:

  • External power stations (plug in types)
  • Regenerative Breaking
  • Generator powered by the combustion engine

Typically, hybrid batteries can last up to 10 years or a mileage of 125,000 miles. A 40kWh Nissan Leaf, for example, has an 8 year warranty and 100,000 miles.

How do they differ from regular car batteries?

In normal car batteries, there are six battery cells sitting in lead acid. In hybrid batteries, there are many ‘dry cells’ that are placed in modules or cassettes and covered in silicone or di-electric gel. Hybrid batteries are larger in size and capacity than normal ones. They also have ‘smarter’ technology to monitor parameters such as amperage and voltage.

Types of Hybrid Batteries

Lithium-Ion (Li-Ion)

Lithium-Ion Batteries comprise of carbon and lithium, similar to ones found on smartphones. They can be smaller in size while storing more energy than other battery types. These batteries also have longer lifespans. They tend to be their most efficient when they are smaller in size. Bigger Li-Ion batteries have issues with overheating and hence reduced efficiency.

Nickel-Metal Hydride (NiMH)

NiMH batteries are the ones found in most hybrid vehicles these days. They are not as expensive as Li-Ion batteries. NiMH batteries have a more stable performance than lithium batteries but tend to lose their charge more easily.

Lead Acid

These have been used for a while in normal cars, and hence, the cheapest hybrid batteries. Its performance is more predictable, and they are safer. They do, however, have lower capacities so you can’t cover much distance on full-electric mode. They are generally used to store the energy from regenerative breaking.

Factors Affecting Hybrid Battery Lifespan and How to Improve It

With hybrid batteries, driver habits can significantly affect the condition and lifespan of the batteries. Some factors that affect battery lifespan include:

Heat

Plugging the battery plug in or exposing it to high temperatures can reduce the battery lifespan.

Overcharging

When the battery has reached its full charge and maximum voltage, keeping the battery exposed to this maximum voltage can damage it. Fortunately, most batteries these days have systems to prevent overheating.

Discharging too fast

Draining the battery too quickly can shorten the lifespan of the battery. This means that you should recharge the battery before it drains down to 5-10%.

Slowing down too quickly

If you regularly decelerate the car abruptly, it can reduce the lifespan. This is because the batteries need time to charge during regenerative braking and braking too fast will interfere with this process.

Improving Lifespans

To prevent a decrease in lifespan, you should avoid making the mistakes mentioned before. Additionally, you should:

  • Do regular check-ups. Ask servicing places if they can check up on the condition of the battery so you can quickly detect any issues.
  • Clean out auxiliary fans. Hybrid batteries are powerful, so they can overheat easily. Hence, it is important to keep the auxiliary fans regularly cleaned since they are there to prevent overheating.
  • Some servicing places could also offer battery reconditioning services, which may save you from buying an expensive new battery.

Feature Image Source

https://commons.wikimedia.org/wiki/File:Nissan_Leaf_012.JPG

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