On September 23, after NIO's 75 kWh ternary lithium iron phosphate standard range battery pack was launched on the NIO App, users left comments with two questions they were most concerned about:
Why is there an extra 5 kWh of battery power? How does the battery degrade at low temperatures?
Users even had a heated debate in the comments section over these 5 kilowatt-hours of electricity.
Once batteries are labeled with lithium iron phosphate, people naturally assume that costs have decreased. In fact, from a cost-reduction perspective, most companies would choose to directly use lithium iron phosphate batteries, like Tesla, which used lithium iron phosphate and increased range while lowering the price, immediately silencing consumer criticism.
However, NIO chose a more complex approach. They used a combination of ternary lithium batteries and lithium iron phosphate batteries, plus 5 kWh of electricity, at the same price, but many users still felt they were losing out.
The main reason for the doubts about the extra 5 kWh is that lithium iron phosphate batteries are cheaper but perform worse than ternary lithium batteries. Therefore, many users feel that NIO is trying to make up for the difference by giving away an extra 5 kWh.
Let's start by talking about the origin of the 75 kWh standard ternary lithium iron phosphate battery pack.
Standard ternary lithium iron phosphate battery pack (75 kWh)
The User-Centric Mindset Behind Giving Away 5 Extra Units
Starting at 2 PM on September 23, pre-orders for the ternary lithium iron phosphate battery pack (75 kWh) will be officially open. New NIO car buyers can choose between the standard range ternary lithium iron phosphate battery pack (75 kWh) or the long range ternary lithium battery pack (100 kWh).
As expected, a 68kWh lithium iron phosphate battery pack should have been released a year ago along with a 100kWh ternary lithium battery pack, but it was rejected by NIO's founder, chairman, and CEO, Li Bin.
A 68kWh lithium iron phosphate battery pack is a typical R&D and cost-driven approach, which is not ideal for a user-centric company. Therefore, Li Bin proposed an idea: "What if we could deliver an extra 5 kWh of electricity?"
Offering users an extra 5kWh at the same price aligns with NIO's user-centric philosophy. Therefore, after a year's delay and a complete overhaul, NIO launched its 75kWh ternary lithium iron phosphate standard range battery pack. This increases the standard range of the same model by 35 kilometers compared to the previous 70kWh ternary lithium battery pack.
In fact, during the Q1 earnings call this year, Li Bin also answered the question of whether or not lithium iron phosphate batteries would be used. He said that lithium iron phosphate batteries have a high cost advantage, but before that, NIO will first solve the user experience of lithium iron phosphate batteries, which will be the core foundation.
NIO is the world's first company to mass-produce a hybrid battery pack using ternary lithium and lithium iron phosphate batteries. While using some lithium iron phosphate batteries may seem like a cost-reducing approach, it actually significantly increases the difficulty of technological development. From cell distribution and dual-system power estimation to the new generation of CTP (Cell to Pack) technology, all of these are entirely new designs and technologies. In the process of developing this new battery pack, NIO obtained more than ten patents and patent applications.
Furthermore, due to increased costs in the manufacturing process, the overall cost of the battery pack has not decreased.
Therefore, in the end, the price remains the same, the driving range increases, and the BaaS price, battery swap benefits, and range upgrade benefits are the same as the original ternary lithium 70 kWh battery pack model, so users do not lose out.
Zeng Shizhe, who is in charge of developing ternary lithium iron phosphate battery packs, said that in actual research and development, all technology development and design are based on big data of user feedback. "We even believe that our 75kWh ternary lithium iron phosphate battery will be much better than many of our competitors' ternary lithium batteries."
During the research and development and design phases, NIO makes corresponding changes and implements closed-loop management for the ternary lithium iron phosphate battery packs based on user feedback every week.
However, the actual performance of this new mixed packaging format remains questionable.
How to overcome technological bottlenecks
Let's start with the most pressing issue: low-temperature degradation.
According to figures released by NIO, its 75kWh ternary lithium iron phosphate battery pack features an all-around thermal insulation design, reducing low-temperature range loss by 25%. Of course, this is in comparison to the low-temperature performance of lithium iron phosphate batteries.
To address the issue of battery degradation at low temperatures, NIO has implemented entirely new designs, from flexible cell arrangement methods and algorithms to barrier methods and active thermal compensation.
In terms of battery pack design, NIO adopts a CTP (Cell-to-Pack) packaging design. Zeng Shizhe said that this design does not have the concept of modules, but determines the position of ternary lithium batteries based on big data analysis. The purpose is to reduce the temperature difference of the entire battery to within three degrees Celsius. Under normal mild operating conditions, it can be reduced to within 1-2 degrees Celsius. Therefore, the number of ternary lithium batteries is different in each corner, with two in the front and four in the back.
The unique dual-system algorithm, based on the low-temperature characteristics of ternary and lithium iron phosphate batteries, performs model-based control and, after multiple rounds of calibration, effectively improves the energy efficiency of the battery system at low temperatures.
Meanwhile, based on the characteristic that the internal resistance of the battery increases at low temperatures, a heat generation model for the battery is developed. Combined with the thermal management of the whole vehicle, the battery control target is dynamically adjusted to achieve a balance between minimizing energy consumption and driving experience.
The heat flow of the entire battery pack is analyzed along all heat dissipation paths. Based on big data analysis, the sources of heat loss in extremely cold weather are identified. By using low thermal conductivity materials and innovative structural design, heat barrier design is implemented at key junctions along all paths, effectively increasing the battery temperature when parked and avoiding energy loss caused by low battery temperature.
In prolonged extremely low-temperature environments, the active radiant heating system balances battery energy consumption and temperature uniformity, ensuring the battery quickly reaches its optimal operating temperature. Under 12 hours of extreme cold conditions, the minimum battery temperature is increased by 40%, and temperature uniformity is improved by 60%.
At the same time, another problem that NIO needs to solve is the SoC (System of Charge) estimation problem.
SoC represents the percentage of battery capacity remaining available, and is one of the most important states in the battery management system. Engineers can use SoC data to match BMS algorithms to accurately display the remaining battery capacity, alleviating users' range anxiety. The higher the SoC estimation accuracy, the more accurately it can display the true range level.
However, compared to ternary lithium batteries, the SoC estimation accuracy of lithium iron phosphate batteries is not high. For new battery systems that mix the two types of cells, estimating the SoC of the new battery system presents a significant challenge to the algorithm.
The technical solution adopted by NIO here is to map the upper and lower limits of the SoC of the ternary lithium battery to the SoC range of the battery system, so as to establish a mapping relationship between the upper and lower limits of the SoC of the ternary lithium battery and the SoC range of the battery system.
Based on the characteristics of ternary lithium and lithium iron phosphate batteries, such as their different self-discharge rates, a high-power battery pack-in-cell DC-DC high-low voltage conversion system was developed for the first time, enabling fast, real-time, and balanced SoC calibration. It also features reduced static power consumption and extended battery life.
By organically combining algorithms, hardware, and dual-system battery cells, accurate SoC estimation is achieved, reducing the calculation error of traditional lithium iron phosphate SoC from 10% to 3%.
Simply put, even if you copy NIO's ternary lithium iron phosphate battery cell arrangement and barrier method, without an algorithm, it's all in vain.
Some other user concerns
NIO also provided detailed answers to questions regarding battery weight, degradation, safety, and calibration issues related to battery swapping.
Compared to a 70 kWh ternary lithium battery pack, it weighs 15 kilograms more.
Regarding battery degradation cycle: During the first year of use, the battery degradation of the standard ternary lithium iron phosphate battery pack will be slightly higher than that of the original ternary lithium (70kWh) battery pack. In the medium to long term, the degradation rates of the two are similar, and both are better than traditional lithium iron phosphate batteries.
Regarding safety: The high temperature of the ternary lithium batteries distributed around the perimeter will spread after being triggered. NIO has conducted many upgrade tests, including multi-point triggering, so even if two points are triggered at the same time, there will be no problem.
Regarding collision safety, Zeng Shizhe stated that many battery packs on the market place the fuse box at the front for ease of assembly. However, in the event of a forward collision, the short circuit point may bypass the front fuse, causing a hazard. The 75kWh ternary lithium iron phosphate battery pack avoids this problem by placing the fuse at the rear.
This design was achieved with the help of CATL, and a structural beam was added to the front compartment. Even after a major collision, there is still space, thus improving the overall collision safety.
Regarding battery swap calibration: NIO's BMS software is compatible with the initial calibration settings of various batteries, and each battery pack has its own unique ID. The BMS will identify the corresponding battery pack based on its ID information, so there is no need to reset it. After swapping it in, it can work adaptively.
In reality, taking a user-centric approach cannot solve all users' problems. Often, some users are very satisfied, while others still have many complaints.
Just like when NIO replaced its battery pack this time, users are still divided into two camps.
NIO's decision to abandon lithium iron phosphate batteries and insist on developing ternary lithium iron phosphate batteries not only increases the difficulty for itself but also seems somewhat thankless.
The market testing and user acceptance of technological iterations always require a process, just like the development of electric vehicles. Without technological iteration, the user experience of electric vehicles will remain in its rudimentary stage, and the electric vehicle market cannot experience rapid development. Battery technology, as part of improving the user experience of electric vehicles, is also undergoing this process.
Creating shortcuts by taking detours is itself one of the characteristics of success for new car brands.
Therefore, we might as well give NIO's ternary lithium iron phosphate batteries some time.
