What do you think of the battery design of Lucid Air Dream?
“My understanding is that if SiC devices are not used for such a large battery, there will be a great loss in overall efficiency, so Lucid also made SiC MOSFETs to improve drive efficiency. We can think that when it reaches 100kWh, if we continue to use traditional IGBTs, it will not be cost-effective in terms of efficiency. This also applies to 20kW on-board chargers.
Lucid Air Dream’s battery system parameters are very high, with a rated capacity of 118 kWh.
There has been some controversy recently: 134 kWh is required to charge from 0-100% in the test.
Here are some fun things to discuss with you, this battery actually reflects a lot of subsequent problems faced by the 110-130kWh large battery system.
▲Figure 1. Lucid’s three-electric technology decryption
Part 1. The charging speed and time of Lucid Air Dream
The maximum charging power of this 118kWh battery can be pulled up to 300kW at a low battery SOC of 1%-20%; then as the SOC increases, when the SOC reaches 50%, the power is about 180kW; to 80%SOC When it is 90kW.
Overall, this power curve is very good for an 800V battery system.
▲Figure 2.Charging power curve of Lucid Air Dream
If you break down according to the charging time, this type of car is expected to form a special usage habit in the future, because it will take too long to be full. The first 100 miles only takes 5.5 minutes, the second 100 miles 6.5 minutes, but the third 100 miles It takes 10 minutes for a mile, and 15 minutes for the fourth 100 mile-this charging time increases quickly.
▲Figure 3. Charging time of Lucid Air Dream
Many consumers are confused by the fact that Electrify America charges 134 kWh of electricity in the 0-100% charging range. My understanding is that during the entire charging process, where is the energy of 16kWh lost? In the following links:
● DC charging pile loss: 3%
This depends on the power consumption of the cooling system and the efficiency of the DC charging module and the power consumption of the billing Display module during the entire process. It is estimated that the total is about 3%, which is about 4kWh.
● Cooling during charging: 4%
This part of the energy is used to cool the battery during the charging process. During the charging process, the water cooling system, 12V DCDC, charging cable, Busbar and battery all heat up.
● Battery efficiency loss: 5%
When high-current fast charging, the actual conversion efficiency of the battery is only about 95%. The difference of about 5% between the input energy and the available energy is the energy lost during the charging process of the battery pack, which includes the charging current, the internal resistance of the cell and other impedances under the entire conduction path, the initial cell temperature, and other battery packs. Equivalent resistance, etc., the entire energy loss is about 6.7kWh.
▲Figure 4. Charging time and required energy
In the test, Taycan is equipped with Performance Plus 94.3kWh (total energy) battery pack to conduct a 0% to 100% DC fast charging test. The available energy of the battery pack is 83.7kWh. Electrify America charges 94 kWh of electricity during the charging process. 10.3 kWh more than the nominal available power.
▲Figure 5. Taycan’s 84kWh available power, charging requires 94kWh
Part 2. How much energy is the battery?
The structure of the Lucid module and battery pack was explained in a previous press conference. I did not follow up at that time.
In fact, a total of 22 modules are used in this design, with a total of 6,600 2170 batteries. As shown in the figure below, a single module actually contains 300 21700 batteries. The configuration specification of the module is 30P10S. The 10 bricks can be seen below, using a plastic and Busbar theme to contain the batteries. Let’s calculate the low voltage of a single module is about 36.5V, and 22 modules are 803V.
▲Figure 6.21700 module group form
The plug-in round wire is used between the modules to implement the connection between the modules.
▲Figure 7. Lucid’s battery module
My understanding is that if SiC devices are not used for such a large battery, there will be a great loss in overall efficiency, so Lucid also made SiC MOSFETs to improve drive efficiency. We can think that when it reaches 100kWh, if we continue to use traditional IGBTs, it will not be cost-effective in terms of efficiency. This also applies to 20kW on-board chargers.
▲Figure 8. The migration of power electrons to SiC or even GAN under large battery capacity is helpful
We will see a situation of 100-120kWh flying in the country in 2022. High-end luxury brands need to increase fast charging speed on the basis of large energy. Dongdong below 100kW is not very good at shooting, at least 200kW, or even 300kW product.