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LFP seems like the silver (or iron?) bullet for EV cars: it's cheaper, more resilient, can be charged to 100% without meaningful degradation, safer, and patent-free. However, the problem with LFP batteries has always been that both volumetric and gravimetric capacity were lower than NCM (or NCA) batteries (1).
This is changing with BYD blade packaging: it promises a 40% volumetric and 60% gravimetric improvement.
To prove its claim, BYD released BYD Seal (aka Ato 4), fitting an 82 kWh LFP battery in the Tesla Model 3/Y form factor.
The only battery-wise issue with BYD Seal is its maximum charging speed, which, in practice, barely reaches 120 kW, much lower than the industry standard. It doesn't seem to be a problem with the battery chemistry itself. Tesla itself started sourcing the same BYD Blade batteries for Berlin-made Standard Range Model Y, and the charging speed is astonishing at approximately 180 kWh peak. If we consider a pack size of 60 kWh, it provides these cells with astonishing sustained charging power per cycle, the same as for the Long Range battery, but this charging is maintained for a longer time than in LR variants.
Despite BYD Seal and Teslas from Grünheide sharing the same cells, charging curves are very different:
If we could extrapolate linearly this charging curve from Tesla SR LFP setup to LR cars' battery capacity (~80kWh), then we would have all the benefits of LFP batteries with even faster charging times (240 kW) than NCA/NCM, and this could dominate the battery market until solid-state batteries become a reality.
However, BYD Seal is NOT charging at 180-240 kWh with the same battery technology. There could be a few possible explanations:
- Tesla is overstressing the LFP battery and shortening its very amazing life to only amazing. BYD would like to build a more reliable reputation for its battery technology. It is not impossible but unlikely.
- A more plausible explanation is that everything boils down (pun intended) to thermal management. The larger BYD Seal pack is more tightly packed, and it is more difficult to maintain the optimal charging temperature. Tesla's smaller pack on a car with a similar footprint has more room to control cooling and heating of the battery pack.
If these problems could be overcome, we could have a tectonic shift in EV affordability, sustainability, and longevity. I wish I am proved wrong, and what is holding us back are non-technical obstacles. In the meanwhile…
What about a Tesla with an 82 kWh LFP pack?
Would it be better for Tesla buyers, Tesla to follow BYD Seal and upgrade to a 60 kWh LFP Tesla or an 82 kWh LFP in lower trim models and compromise on lower charging speeds? The answer is not so straightforward. While range is king when it comes to EV choice, charging speed is an overlooked factor. Here is a small experiment:
I modelled a trip from Berlin to Innsbruck for two cars with the same consumption characteristics but charging characteristics of:
- a car with 60kWh BYD Blade batteries and Tesla's charging curve
- a car with 82kWh BYD Blade batteries and BYD Seal charging curve
To do so, I am using the routing demo tool from HERE Technologies, which allows parameterizing and modeling any type of EV:
- 60 kWh pack, 172 kW peak charging: Trip duration with charging: 8h 55m
- 82 kWh pack, 120 kW peak charging: Trip duration with charging: 8h 58m
(Your results could vary as live traffic is considered)
Surprisingly, the car with the smaller battery has a marginally better time than the car with a larger battery (2). While there are benefits to a larger battery pack, they are not as significant as they seem on the surface. If upgrading the battery pack size for SR vehicles would mean compromising charging speed, in practical terms, the benefits are not as pronounced as it would intuitively seem.
(1) There are a few other minor issues with LFP, like operational efficiency in lower temperatures and a flat voltage curve, which makes battery SoC more challenging.
(2) This model ignores the weight difference of a car with a larger battery pack and assumes the same energy requirements. The change in highway consumption will be, however, less than 2%.
Sources:
BYOD Seal charging curve: https://www.youtube.com/watch?v=vPUYS5xLfJ8
Tesla 60kw BYD charging curve: eivissa/TFF Forum https://tff-forum.de/
BYD Blade Battery: https://medium.com/batterybits/the-next-generation-battery-pack-design-from-the-byd-blade-cell-to-module-free-battery-pack-2b507d4746d1