In Depth: Mazda i-Eloop

Mazda wants you to save fuel while being able to maintain the fun to drive factor that their cars are known for. One way they’ve done that is by using SkyActiv technology in their recent vehicles. But they have another trick up their sleeve. That trick is Mazda i-Eloop.

i-Eloop stands for Intelligent Energy Loop. It’s a brake energy regeneration system. Normally when you hit the brake pedal in a car, the kinetic energy that the braking process creates is simply lost. Mazda uses this to power to relieve the engine from the need to produce this electricity for your in-car stereo, navigation system, lights, and anything else electrical. By recovering and reusing the energy that is produced when a car decelerates, Mazda can get significant improvements in fuel economy. Before I tell you how it works, let’s look at the parts that make up the i-Eloop system:

  • Variable voltage alternator: Responding to voltage level charges in the capacitor, the alternator automatically varies its voltage (between 12V and 25V) in order to smoothly transfer electricity to the capacitor.
  • Electric Double Layer Capacitor: An electricity storage device similar to a battery. but it does not involve a chemical reaction.
  • DC/DC convertor: Converts the voltage of electricity from the capacitor (max. 25V) to 12V in order to supply power to the electrical components. 

The first thing you notice is that there is no battery. The reason is simple. By using a capacitor to store energy you get the following advantages:

  • You get a power density of over 10kW/kg which is something that a battery (lithium-ion or lead acid) can’t come close to.
  • It is capable of charging and discharging a large amount of energy at once. That’s another thing that batteries can’t match.
  • There’s a very low amount of deterioration after repeated charging and discharging. A battery has to be replaced eventually. Usually within a few years at a cost to you.
  • The capacitor mainly consists of activated carbon which is derived from coconut husks. No precious metals or heavy metals are used. That means it’s environmentally friendly.
  • Capacitors unlike batteries can work at higher ambient temperatures making it possible to locate it in the engine bay. Batteries in hybrids are typically in the trunk which affects how the car can handle and reduces the available storage space in the trunk.

Now how does i-Eloop work? When the accelerator is released, a high-performance alternator powered by torque from the tires generates electric energy which is quickly transferred to the capacitor. Now when you accelerate, the alternator does not generate electricity. Instead, the capacitor generates the electricity. The fact that the engine is not generating electricity means that it can be turned off at stop lights automatically and automatically turned on when you let go of the brakes. Mazda calls the automatic stop/start functionality i-Stop and in combination with i-Eloop, it can deliver up to a 10% savings in fuel. Now if the electricity available exceeds what the car is actually using, the excess electricity is used to charge the lead-acid battery that starts the car.

Another thing to note is that Mazda paid special attention to ensure that the system produces the maximum power generating torque for a given degree of deceleration but does not itself produce unnecessary deceleration which may annoy the driver. For example, if you drive a typical hybrid, hitting the brakes feels very weird and disconnected. That drives some people (like me for example) nuts. So the fact that Mazda looked after that is great.

This technology is available as an option in the Mazda6 and Mazda3. I’m sure it will be making an appearance in other Mazda vehicles eventually. That way regardless of what Mazda you drive, you can get better fuel economy while keeping the fun to drive factor. This is an option that’s very much looking into if you’re in the market for a car from Mazda.

5 Responses to “In Depth: Mazda i-Eloop”

  1. Why is a special battery required for I eloop?

    • Christopher Says:

      Unlike conventional batteries, capacitors can charge very quickly. However, also unlike batteries, they don’t typically hold a charge very long which makes them perfect for this type of scenario.

  2. Jim Simonin Says:

    So just how expensive is replacing this special alternator and special capacitor?

  3. This technology is great. Its nice that Mazda has thought about fuel conservation. The one thing which has surprised me a lot is that it doesn’t have car battery. How much time do the capacitors take to charge?

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