How much does an internal combustion engine weigh in a car and is 300 kg of batteries really much more? [WE BELIEVE]

Recently, we have heard the opinion that internal combustion vehicles or plug-in hybrids use energy more efficiently because "engines weigh 100 kg, and the battery in an electric car is 300 kg." In other words: it makes no sense to carry a huge battery, the ideal is a set in a plug-in hybrid. That is why we decided to check how much an internal combustion engine weighs and calculate whether the weight of the battery is really such an issue.

Table of contents

• Internal combustion engine weight versus battery weight
  • How much does an internal combustion engine weigh?
    • Maybe better in plug-in hybrids? What about the Chevrolet Volt / Opel Ampera?
    • And what about a minimal option like BMW i3 REx?

Let's start by answering a question that may seem obvious: why are we considering the battery itself, if the electric vehicle also has an inverter or a motor? We answer: firstly, because it was formulated this way 🙂 But also because the battery makes up a significant part of the mass of the entire electric drive.

And now the numbers: the Renault Zoe ZE 40 battery with a useful capacity of 41 kWh weighs 300 kilograms (a source). The Nissan Leaf is very similar. About 60-65 percent of the weight of this design is made up of cells, so we can either 1) increase their density (and battery capacity) with a slight increase in weight, or 2) maintain a certain capacity and gradually reduce the weight of the battery. battery. It seems to us that Renault Zoe vehicles up to 50 kWh will go along track 1 and then along track 2.

In any case, today a 300-kilogram battery can drive 220-270 kilometers in mixed mode. Not so little, but trips to Poland already need to be planned.

> Electric car and traveling with children – Renault Zoe in Poland [IMPRESSIONS, range test]

How much does an internal combustion engine weigh?

The Renault Zoe is a B segment car, so it's best to use an engine from a similar segment car. A good example here are Volkswagen's TSI engines, which the manufacturer boasted about their compact and extremely lightweight design. And indeed: 1.2 TSI weighs 96 kg, 1.4 TSI - 106 kg (source, EA211). Therefore, we can assume that a small internal combustion engine actually weighs about 100 kg.... This is three times less than that of a battery.

Only that this is just the beginning of weighing, because to this weight you need to add:

• lubricants, because engines are always weighed dry - a few kilograms,
• Exhaust systembecause without them you can not move - a few kilograms,
• coolant radiatorm, because the internal combustion engine always converts more than half of the energy from fuel into heat - a dozen + kilograms,
• fuel tank with fuel and pumpbecause without them the car will not go - several tens of kilograms (falls while driving),
• gearbox with clutch and oilBecause today only electric vehicles have one gear - several tens of kilograms.

Weights are inaccurate because they are not easy to find. However, you can see that the entire combustion engine easily penetrates 200 kilograms and approaches 250 kilograms... The difference in weight between an internal combustion engine and a battery in our comparison is about 60-70 kg (20-23 percent of the battery's weight), which is not that much. We expect them to be completely destroyed in the next 2-3 years.

Maybe better in plug-in hybrids? What about the Chevrolet Volt / Opel Ampera?

Volt/Amp is a very bad and unfavorable example for those who think that "it is better to carry an internal combustion engine with you than a 300 kg battery". Why? Yes, the internal combustion engine of the car weighs 100 kg, but the transmission in the first versions weighed, note, 167 kg, and from the 2016 model - “only” 122 kilograms (source). Its weight is due to the fact that it is an interesting example of advanced technology that combines several modes of operation in one housing, connecting an internal combustion engine with an electric one in various ways. We add that most of the gearbox would be superfluous if the car did not have an internal combustion engine.

After adding an exhaust system, a liquid cooler and a fuel tank, we can easily reach 300 kilograms. With a newer transmission, because with the old one we will jump over this limit by several tens of kilograms.

> Chevrolet Volt drops out of offer. Chevrolet Cruze and Cadillac CT6 will also disappear

And what about a minimal option like BMW i3 REx?

In fact, the BMW i3 REx is an interesting example: a car's internal combustion engine only works as a power generator. It doesn't have the physical ability to drive the wheels, so the complicated and heavy Volt gearbox isn't needed here. The engine has a volume of 650 cc.³ and has the designation W20K06U0. Interestingly, it is produced by Taiwanese Kymco..

The BMW i3 REx combustion engine is located to the left of the box with orange high voltage cables connected. There is a cylindrical muffler behind the box. At the bottom of the picture you can see a battery with cells (c) from BMW.

It is difficult to find its weight on the Internet, but, fortunately, there is a simpler way: just compare the weight of the BMW i3 REx and i3, which differ only in the combustion energy generator. What is the difference? 138 kilograms (technical data here). In this case, there is already oil in the engine and fuel in the tank. Is it better to carry such an engine, or maybe a 138 kilogram battery? Here's the important information:

• in the mode of continuous recharging of the battery, the internal combustion engine makes noise, so there is no silence for the electrician (but above 80-90 km / h the differences are no longer noticeable),
• in the mode of almost discharged battery charging, the power of the internal combustion engine is insufficient for normal driving; the car hardly accelerates above 60 km / h and can slow down on descents (!),
• in turn, that 138 kg of the internal combustion engine could theoretically * be exchanged for 15-20 kWh of battery (19 kWh of the Renault Zoe battery described above), which would be enough to drive another 100-130 km.

The electric BMW i3 (2019) has a range of around 233 kilometers. If the extra mass of the BMW i3 REx (2019) internal combustion engine had been used, the car could travel 330-360 kilometers on a single charge.

Choosing batteries. The energy density in the cells is constantly increasing, but to continue the work there must be people willing to pay for the transition stages.

> How has battery density changed over the years and have we really not made progress in this area? [WE WILL ANSWER]

*) The BMW i3 battery fills almost the entire chassis of the vehicle. Modern technologies for the production of cells do not allow filling the space left from the internal combustion engine with a battery with a capacity of 15-20 kWh, because there is not enough of it. However, this excess mass can be better dealt with year after year by using cells with increasingly higher energy densities. It happened in generations (2017) and (2019).

Opening image: Audi A3 e-tron, a plug-in hybrid with combustion engine, electric motor and batteries.

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