Why no Full Electric Car Races at Le Mans?

Electric Vehicles and Le Mans. Top right: Mission H24 Hydrogen Fuel Cell Electric Vehicle. Bottom left: Module of a Full Electric HyperCar. Image credit: Dr Cecile Pera

The idea behind the first 24h of Le Mans Race back in 1923 was to test endurance of cars because, at that time, it was not possible to make a long journey without stopping to clean or to change some components (spark plugs, for example). The 24h of Le Mans has now become the most prestigious Endurance race.

Many Engine Technologies have been developed for Le Mans such as the TurboCharger (Porsche at Le Mans in 1974), the dual Clutch (Porsche at Le Mans in 1987) or more recently the Hybridisation (Audi eTron 1st Hybrid Car to win Le Mans in 2012)

If Le Mans has always been precursor of the next big trend in the Automotive Industry, why do we not see any full electric cars there? Why no car manufacturers or high performance teams feature 100% BEV and why not win the title?

1- Le Mans: Some Order of Magnitude

1- The average speed at Le Mans is about 225 km/h and even 250 km/h in qualification

2- Cars run for about 13-14 Laps = around 180 km before refuelling which is about 40-45 min

3- Pit-stop is around 1 minute (if it includes a tyre change)

4- LMP1 and LMPH weights are about 833 kg and 840 kg, respectively

To be competitive (understand not to look too ridiculous), a Battery Electric Vehicles would have to be able to near these values which can be translated into Battery Technology constrains:

1- The Battery cells would require a very high Power density (= kW that can be delivered)

2- The Battery Pack must be light-enough to allow the car to be under 900 kg

3- Very Fast Charging would be an absolutely requirement because anything longer than 3 min would be ridiculous

4- The Battery would need to get quite good capacity (=kWh that can be delivered) to achieve a long-enough Range

2- Rimac Nevera as a HyperCar Benchmark

Images credit: RIMAC

Even if there are quite a lot of development for Fully Electric HyperCars (NIO EP6, RIMAC Nevera, Lotus Evija, Aspark Owl…), there are not that many to buy today.

Let’s work on the RIMAC Nevera as our benchmark for some quick estimations. The RIMAC Nevera

1- The Nevera top speed is 412 km/h ✅

2- I do not know the weight of the RIMAC Battery Pack but the car on itself is about 1950 kg which is nothing near a Le Mans car ❌

3- Mate Rimac himself did set up the charging record of its own car on a 300 kW Ionity charger in 21 minute for 10-80%. RIMAC mentioned that the Nevera can accept 500 kW charging but that would still require at least 14 min for 10-80%, which is far too long. Even if we could double the charging speed, losing 6min per pit stop compared to other cars is losing the race ❌

4- The Nevera Range is 550 km but on a WLTP and very certainly not driving at 220 km/h. The Nevera electric consumption when driving full speed is not in the public domain. But we can still estimate what would be this consumption. For this, let’s talk about the Porsche Taycan. The Porsche Taycan is given for a consumption of about 18 kWh/100 km (it depends on the model but ballpark, it is around this value). Auto Bild measured an Energy consumption of 118 kW / 100km driving the Porsche Taycan 4S full speed on the highway. This is about 6.5 times the WLTP value. As an estimation, let’s consider a value of 6 (because I like to be nice) which gives us a Range of 90 km for the RIMAC Nevera.

90 km is about 6.7 Laps at Le Mans. Some important remarks: (1) there is no half-Lap at Le Mans so this would mean 6 Laps, not 7; (2) No reasonable person would risk to drive the Battery up to the limit because any red flag that would prevent you to access the pits would get you out of the race, so that a contingency of at least 1 Lap is necessary.

So, today, I estimate that a Nevera could probably make 5 Laps of Le Mans before recharging. ❌

3- Formula E/Best Possible Benchmarking

Image Credit: AUDI

OK, maybe the RIMAC is not adapted for this Benchmark so as another High Performance, let’s talk about Formula E Battery Generation 3.

1- Formula E Gen 3 top speed is about 320 km/h ✅

2-Formula E Gen 3 Weight is about 840 kg including the driver ✅. Nevertheless, this weight is valid for a 50 kWh Battery size that weighs 284 kg. Also in Formula E, the Battery Pack does not require to be Very Fast Charge, knowing that this would be extremely challenging for the Battery cooling, probably requiring a modification (and so a heavier Battery Pack). As a ballpark number, we can estimate that a 100 kWh Battery able to withstand Le Mans numerous very fast charging would be around 600 kg, which would probably overweight the car by at least 300 kg so 🤨❌

3- It is difficult to estimate the fastest possible Charging time. I personally believe that fast charging at 10 C would be really impressive and that still means around 10 min for charging a 100 kWh Battery Pack. Today, there is no technology able to recharge a 100 kWh Battery Pack in 1 or even 3 minutes.

Let’s talk about the Battery Swapping option because after all, this is what the NIO EP9 does. From a security point of view, it is a hard sell at Le Mans: first because of the High Voltage risk when handled by humans in a very stressed environment but also because such a Battery would be very heavy (the EP9 actually has 2 side Batteries). In the case of the EP9, the Swaps are possible because they reduce the waiting time between 2 sessions but it would be very hard to have a constant 24h race based on very frequent Battery Swapping. So the conclusion on the charging time is a definite ❌

4- About the Range, let’s pick up one of the fastest track: Mexico City. This year (2022) the winner drove 104.2 km in 48min28s which corresponds to an average speed of about 130 km/h (which is about half the speed we need for Le Mans by the way). We can estimate that the consumption is about 50 kW / 100 km (even if it probably slightly less because the car may not be finishing at 0 SOC).

So, to be able to make 13-14 Laps of Le Mans (180 km), a formula E would require a Battery capacity of about 100 kWh, but that would only correspond to an average speed of 130 km/h. If you assume an average speed of 225 km/h, this reduces the range by about 50% (keep in mind it is non-linear) which gives us only 6-7 Laps of autonomy. Another option is to use a 200 kWh Battery Pack, which is not realistic.

You are not convinced? Let’s estimate this range by another method: at Le Mans, following Le Mans rules, fuel mass flow is limited to 80.2 kg of fuel / hour. This means about 396 kWh of energy for 100 km. Of course, the IC Engine Efficiency is far from 100% efficient. As Le Mans Engines are among the most efficient Engines, I will assume here that the efficiency is about 50% (OK 48% if you want but it does not change the estimation) which means that a car requires about 200 kWh of energy to be able to cover 100 km, which is by the way the exact same conclusion as the paragraph above.

Anyway, this makes the conclusion about the BEV autonomy for a Race like Le Mans a big ❌

4- Will we see a BEV at Le Mans soon?

Mission H24 Hydrogen Fuel Cell Electric Car to race at Le Mans. Image credit: Dr Cecile Pera

Big disclaimer: there will not be any Fully Electric car racing at Le Mans in the near future. Keep in mind that the Hydrogen Fuel Cell Electric car of Mission H24 is already in discussion to be at Le Mans since 2018 (but the 1st version of this FCEV from Green GT car had been considered for Le Mans since 2014), is participating as a “guest” under demonstration at Le Mans in 2022 and will only officially enter the competition in 2024.

It is important to understand that accepting a new category of cars is always a risk for the organisation because, if the car is too slow or too unreliable, it creates a safety risk (you cannot get cars running at 170 km/h in the middle of cars at 350 km/h).

That is why there is a very serious evaluation of these new technologies before they can enter the true Le Mans Race. To be accepted, a BEV car will have first to go through an evaluation in what is called “Garage 56”. Garage 56 cars correspond to cars that do not have to fulfil an existing regulation (as you guess, there is no regulation written for BEV at Le Mans). As a counterpart, it is not officially classified at the end of the race.

But for sure, car manufacturers, the FIA and all the business would benefit to feature a fully Electric Vehicle at Le Mans. In the assumption, the acceptation time for Garage56 can be reduced to 3-4 years, I personally do not imagine to see a BEV officially racing at Le Mans before 2026.

5- Technologies and Challenges

Battery Pack and cooling of the InMotion Racing Vehicle

As we have seen in this article, not surprisingly, Range and Charging time are 2 major problems. But what is difficult to understand is that both constraints oppose each other. Range means kWh (capacity) while charging time means kW (charge/discharge time).

The problem is that today Cell Chemistries can only optimise one of these constraints. The graph below locates various available cell chemistries on a chart (Energy density x Power density). This graph is extracted from the PodCast Ask a Nerd Ep3 with David White from Danecca. On this graph, all the cells have the same format (cylindrical) and they are all manufactured by Samsung. Today, there is no chemistry able to offer very long range (high Energy) with very high power density at the same time. The closer to this are Formula E Batteries that we have seen are already far below the Le Mans requirements.

Characterisation in Energy and Power of various Samsung Cells (cylindrical). Image extracted of the PodCast Ask a Nerd Ep 3: Fast Charging and Small Battery Design

Of course, Battery Cells and Chemistry evolve each day and probably will achieve this point in a near future but it is difficult to say when and with which Technology (maybe not Lithium Batteries, there are tons of other chemistries under development)

Another problem is about the charging that requires very high power charging infrastructure at Le Mans, we are talking here about 2-4 MW.

Nevertheless, there are projects under development that come closer to be considered. Among the publicly known project, we can cite the InMotion Racing Electric Car developed with the Very Fast Charging capability of Heliox.

The InMotion car today uses a 58 kWh Battery with a range of about 35-40 km but the interesting point is that it is able to recharge in only 12 min (C-rate of 5) and they believe they can make soon 6-7 min. Nevertheless, their estimation is still that a 200 kWh Battery Pack would be necessary to achieve a range of 8 laps a Le Mans. In this case, if they want to target a reasonable charging time - let’s say 3 min - this would require a charging power of 720,000,000 J / 180s = 4 MW! Assuming you would recharge between 20 and 80% this still means a 2.4 MW charger (but in this case you are using only 120 kWh of the Battery Capacity).

This is anyway fascinating to follow the development of racing BEV Hypercar and I do hope that I will soon be able to say that this article is outdated as one of ideally several fully electric vehicles will be able to integrate Le Mans. Stay tuned…