Lucid Air DC Fast Charge Follow Up: Charging Losses Explained

A few days ago, we posted a video of a Lucid Air completing a full 0 to 100% DC fast charge session on an Electrify America 350 kW charging station. It was the very first time such a video had been made available to the public and it created quite a stir in the EV community, both positive and some, well, not so positive. 

Most of the comments on the YouTube video, Twitter, and the article here on InsideEVs were about how the Air is a great charging EV as it can add miles of range back faster than any other EV that we’ve seen so far. However, we also had a known Tesla YouTuber, Warren Redlich, take our video and use it as “evidence” to create his own video to prove a claim he’s been making for a while now, that Lucid is lying and that its battery is much bigger than the 118 kWh capacity they have claimed. 

Normally, we wouldn’t respond to something like this, but in this case, there were dozens of comments made by followers of Redlich on the video and Twitter that suggested InsideEVs and me personally, were lying, and covering up for Lucid. So when your integrity is called into question, we think it’s appropriate to respond. Additionally, a lot of people new to EVs that don’t understand battery tech and charging may watch Redlich’s video and be misled on how this all works.

After watching Redlich’s video, many of his followers then went online to perpetuate the misunderstanding that our charging session proved the battery is larger than 118 kWh.

So how did we allegedly “prove” that Lucid is lying about the size of its battery pack? We did so by showing the entire 0 to 100% charging session, and at the end, the Electrify America station billed us for 134 kWh of dispensed energy. Redlich took the 134 kWh as proof that the Air’s battery is more than 130 kWh, not the 118 kWh that Lucid states. 

What accounts for EV charging losses?

The problem with this battery size discrepancy is that during the charging process, energy is lost in a variety of manners, and it all adds up to create significant charging inefficiencies. Infrastructure companies like Electrify America charge their customers for the gross amount of energy they use during the session, not the net amount of energy that makes its way into the battery pack. 

The billed amount will always be more, due to losses, and it can be anywhere from 5-6% all the way to 15% or more, depending on a variety of factors. Charging losses occur in both lower-powered AC charging and high-powered DC fast charging. In AC charging, the losses are lower in real-time, but since you need to charge for many continuous hours, they add up and can be even higher than the losses for DC fast charging, but again, that’s dependant on a lot of factors (AC charge rate, the efficiency of the onboard charger, temperature, EVSE, etc)

The video in question is based on incorrect assumptions

So let’s take a look at how charging losses add up during high-speed DC fast charging. It’s notable to point out that the Lucid Air accepted higher charging power, 304 kW, than any electric vehicle we’ve ever tested. Higher power charging will create more heat losses across the various components involved in the charging process, from the actual charging station all the way to the battery in the car. 

Additionally, these are estimates. The car, the charging station, the ambient temperature, and a lot of other factors will ultimately dictate how much energy is lost in any one particular charging session.

For DC fast charging, it’s typical during extremely high-powered charging rates like what the Air can accept that around 3% of energy is dissipated to heat in the charging station – this energy never makes its way out of the charging station, but you have to pay for it because its a cost to the infrastructure company. Charging station losses include conversion losses incurred during the power conversion from AC to DC at the DC charging station, the cooling of the charger and cables. This can add up to about 3%, and 3% of 134 kWh is about 4 kWh.

Next, approximately 4% of the dispensed energy is used to cool the battery during the charging process. During charging, the input energy that is delivered to the vehicle goes into several energy components, namely cooling energy, ancillary 12V energy, dissipated heat into the cables, bus bars and cells, and battery stored energy. The compressor power for example can be at 5kW average during a charging session.

The higher the charging rate, the more heat is created and the battery & components must be cooled down or they will sustain damage. If you’ve ever stood next to a Tesla on a V3 Supercharger you’ll hear the fans working furiously to keep things cool so the vehicle can continue to accept up the maximum charge rate of up to 250 kW. All that uses about 4% of the delivered energy and 4% of 134 kWh is about 5.4 kWh.

Finally, battery efficiency is only about 95% during fast charging. The roughly 5% difference in the input energy and the usable energy is the energy lost during charging as well as discharging in the pack. The heat generated inside the pack during fast charging depends on several factors, namely charging current, the internal resistance of the battery cells and conductive path, initial battery cell temperature, battery pack resistance, etc.

Additionally, battery capacities are rated based on discharging (usable) energy, not the charging energy. During discharge, especially when high power is demanded from the system, some of the energy stored in the pack will be lost as heat and thus the usable energy will effectively be less than the stored energy. 5% of 134 kWh is about 6.7 kWh.

That all adds up to a total estimated loss of about 15 kWh. If you subtract 15 kWh from the 134 kWh that the Electrify America charging station billed us for, you arrive at 119 kWh, one more kWh than Lucid claims its pack is. If the Air’s pack is indeed 118 kWh as Lucid claims, we experienced a loss of 16 kW, which is a 13.5% loss, and very close to what we would expect to see on an EV charging at such a high rate. 

It’s important to note that these numbers are estimates, not exact values. As mentioned, charging losses will vary from charging session to charging session, and are dependant on a number of variables. I’ve discussed this subject with battery tech engineers from a variety of OEMs over the years. Quite often I’m told the industry average is about 10% as there are inefficiencies in the charging process for all EVs – however, some are better than others and the EVs that charge at lower rates usually have slightly less charging losses.

Additionally, we’re not making claims on exactly what size Lucid’s battery pack is. We don’t know for sure exactly how large is it. However, we’ve been doing EV charging evaluation for a long time, and have charged just about every production electric vehicle made to date. Our experience leads us to believe that the usable capacity of the battery pack in the Lucid Air Dream Edition is extremely close to 120 kWh. The gross capacity is an entirely different subject, which we’ll get into next.

Are 13.5% charging losses on the high side? Yes. absolutely. We have observed as little as 6% charging losses when we have DC fast charge tested other EVs. However, they charge at a lower rate and create less heat while charging. Therefore, we would expect to see less loss from heat. Additionally, Lucid has never claimed the Air has low charging losses, its own EPA filing (which we’ll look at later in the post) explicitly admits 14% charging losses. 

Porsche Taycan charging losses are similar

A Porsche Taycan after charging from 0 to 99% has taken in 94 kWh with a battery that has a usable capacity of 83.7 kWh. The 10+ kWh were lost to charging inefficiencies

We recently conducted our 0 to 100% DC fast charge test on a 2021 Porsche Taycan with the Performance Plus 94.3 kWh (total energy) battery pack which has 83.7 kWh usable energy. The Electrify America charging station dispensed 94 kWh during the session which is 10.3 kWh more than the Taycan’s battery can accept. We’ll have the video and analysis up on InsideEVs tomorrow. 

That equates to an 11% charging loss which is similar to the 10% to 12% industry average we expect with electric vehicles that charge at very high rates. The Taycan is one of the best charging electric vehicles available today, and some experts viewed it as the best before the Lucid Air launched.

The Taycan still holds a higher charging rate deeper into the pack than the Air does, but since the Air has such a large battery and higher driving efficiency than the Taycan, it can add back driving range faster than the Taycan, or any other EV for that matter. 

We’re not going to spend too much time discussing the total battery pack capacity because it’s not something we can measure from the charging session we did. We can only draw conclusions about the usable capacity from that. We will touch on it briefly though, to give our followers who don’t understand the difference a little information on the topic. 

The total, (or gross) capacity of a battery pack is the amount of energy it can store when it’s fully charged to 100% The usable capacity is how much energy the user is allowed to access. The usable capacity vs. the total capacity can vary depending on the battery chemistry as some types of lithium-ion batteries are better suited to be charged to 100%, while others will degrade faster if the battery is frequently charged to 100%

Therefore, EV manufacturers all have different policies on how much battery they hold in reserve as a “buffer” to prolong the life of the battery. The energy in that buffer isn’t accessible to the user. For instance, the Volkswagen ID.4 has an 82 kWh battery, however, only 77 kWh is accessible. Volkswagen holds a 5 kWh buffer in an effort to extend the battery life. 

Some OEMs, like Porsche, Audi, and Ford are conservative and hold a large battery buffer on their EVs. Others, like Tesla, Volvo, and Lucid are more liberal, and allow the user to access nearly 100% of the battery pack. However, they then strongly recommend that the user only charge the vehicle to 80% for daily charging, because they know if the battery is charged to 100% every day, it will degrade faster than it would otherwise. 

Which strategy is better? It’s hard to say, but by opening up more of the battery’s total capacity, the OEM can claim the vehicle has a longer driving range than what it will typically have on any given day when charged to 80%. However, the extra range is there when needed. I personally own a Tesla Model 3 and usually charge it to about 80% for daily use. But on the days I need to take it on a long road trip, I can charge to 100% and have the additional 50 to 60 miles of driving range.

However, if the owner doesn’t abide by the manufacturer’s recommendation and charges the vehicle to 100% every day, they will most likely experience more battery capacity loss sooner than they should have and will permanently decrease the vehicle’s driving range. 

As for the total capacity of the Lucid Air Dream Edition, we can’t be sure, but based on the EPA filing, it does appear the gross capacity is about 120 kWh. Again, that lines up with Lucid’s claim that the Air Dream Edition has a 118 kWh battery combined with the fact that it advises customers to charge the Air to 80% for daily charging. When the manufacturer does that, it often means it allows nearly the entire pack to be accessed when charged to 100%. 

To properly calculate battery pack size you need to use nominal voltage, not peak voltage as was used in the tweet above. We explain that in the EPA filing info below.

No standard method of reporting charging energy

Part of the reason why there is so much confusion and speculation is that there isn’t one standard by which charging stations and electric vehicles display the energy delivered. Tesla Superchargers for instance do not have a display. They rely on the vehicle to display the energy received. However, the car only shows the net energy it receives, not the gross.

Therefore, you don’t get a full picture of how much energy was dispensed, and it gives the impression that the vehicle is 99% efficient when charging – and that’s not the case. The video questioning the capacity used a recent Car and Driver article in which they claimed the Model S was 99% efficient when Supercharging because they evidently don’t quite understand EV charging either. This is new to everyone and it’s going to take a while before the traditional car review outlets understand the intricacies of electric vehicles as thoroughly as EV-specialist sites like InsideEVs do. 

It would be great for the entire industry if all charging stations displayed the same information, and all the EVs showed the same charging data inside the vehicle. That way, consumers (and journalists) would have an apples-to-apples comparison. It would help EV owners better understand the real amount of energy that it took to fill their pack. Currently, most EVs don’t even show you the amount of energy the car took in during the session, only the estimated miles added. Personally, I’d like to see both. 

Additionally, not all manufacturers even disclose the exact total and usable battery capacity of their EVs, so owners are left to guess, or look it up in the EPA filings. 

Tesla Bjorn has actually done some good real-world testing of charging efficiency in Teslas, and we urge you to look at his YouTube channel if you’re interested in exploring this topic further. 

Lucid Air’s battery size and charging efficiency as compared to the Tesla Model S Plaid

Since incorrect Tesla Supercharging efficiency was used to push the narrative that Lucid is being untruthful with its pack size, we decided to take a look at Tesla’s Model S Plaid EPA filing and compare it to Lucid’s. From this, we can see the charging losses as well as the battery capacity of both vehicles. 

Page 16: The usable nominal energy of the Dream Edition Range and Performance is 118 kWh. 

Page 16: The nominal voltage of the Dream Edition Range & Performance is 800 V. 

Page 23: The battery capacity of the Dream Edition Range & Performance is 150 Ah. 

The approximation of net energy for the Lucid Dream Edition Range & Performance can be estimated by the following:

Page 16: The Lucid Air battery uses 6,600 21700 cells. 220 series x 30 parallel = 6,600 cells.

Using 220 series, 3.636 V nominal cell voltage, the pack nominal voltage is 800 V. 

Using 220 series, 4.2 V peak cell voltage, the pack peak voltage is 924 V.

Usable Energy = nominal voltage times the capacity = 800 x 150 = 120 kWh (slightly higher than 118 kWh – but this is only an approximation of net energy). 

Page 30: The battery recharge energy is 137.3 kWh. The total charged energy of 137.3 kWh includes the losses/consumption incurred while charging and the battery stored energy, leading to an overall 86% charging efficiency and 118 kWh usable energy. 14% charging losses are thus expected.

Page 56: The usable nominal energy of the Tesla Model S Plaid is 99.3 kWh 

Page 15: The nominal voltage of the Tesla Model S Plaid is 410 V 

Page 23: The battery capacity of the Tesla Model S Plaid is 256 Ah 

The approximation of net energy for the Tesla Model S Plaid can be estimated by the following:

Page 16: The Model S Plaid battery uses 7,920 18650 cells. 110 series x 72 parallel =7,920 cells.

Using 110 series, 3.72 V nominal cell voltage, the pack nominal voltage is 410 V.

Using 110 series, 4.2 V peak cell voltage, the pack peak voltage is 462 V.

Usable Energy = nominal voltage times the capacity = 410 x 256 = 104.9 kWh (slightly higher than 99.3 kWh – but again, this is only an approximation of net energy). 

Page 67: The battery recharge energy is 116.34 kWh. The total charged energy of 116.34 kWh includes the charging losses as well as the battery stored energy, leading to an overall 85% charging efficiency and 99.3 kWh usable energy. 15% charging losses are thus expected. 

Conclusion:

As you can see, the Model S Plaid actually documents slightly higher charging losses in its EPA filing than that Lucid Air did, 15% compared to 14%. However, the EPA filings only require AC charging data, not DC fast charging information, and as we mention above there are differences, and the charging results depend on a variety of outside factors. 

Still, based on the official EPA filings, in our opinion, if one were to accept the fact that the Tesla Model S has a 99.3 kWh battery pack, one should also accept the fact that the Lucid Air Dream Edition has a 118 kWh pack. I suppose it’s only a matter of time before an independent 3rd party tears one of these babies apart and lays the issue to rest, once and for all.

If only there was a well-known and respected automotive teardown specialist out there to do such a thing.

We hope this article helped explain how battery capacity and charging losses works. As always, let us know your thoughts in the comment section below.