Why some electric cars need to be charged to 80% and others to 100%

When we talk about electric cars, attention is often focused on their design, their autonomy, or even their acceleration. However, a less visible but equally crucial element deserves our attention: the battery. Between Lithium Iron Phosphate (LFP) and Nickel-Manganese-Cobalt (NMC), there are differences that you need to know.

When it comes to electric cars, battery charging turns out to be a complex subject. Between myths and realities, the practice of charging your electric car to 80% or 100% is deeply rooted in the science of its battery.

Understanding the difference between lithium iron phosphate (LFP) and nickel-manganese-cobalt (NMC) batteries is not just a matter of curiosity; it is a necessity for any owner concerned about the longevity and performance of their electric car.

The science behind LFP and NMC batteries

The fundamental difference between LFP and NMC batteries lies in their chemical composition, both at the cathode and anode level, which directly influence their charge management. While LFP batteries use lithium iron phosphate as the cathode material, NMC batteries use an alloy of nickel, manganese and cobalt. This distinction is not small, as it impacts the capacity, lifespan, and heat resistance of the battery.

Beyond the cathode, the composition of the anode also plays an important role. Both LFP and NMC are based on lithium, but their chemical reaction differs depending on the cathode material, thus influencing energy density, thermal stability and longevity.

LFP batteries offer better thermal stability and are less prone to degradation, while NMCs, despite having a higher energy density, require more care when charging due to their more reactive composition.

Why this difference in treatment?

LFP batteries, known for their robustness, are less likely to overheat and have a longer lifespan. This allows them to tolerate a full load of up to 100% without significant impact on their long-term health.

On the other hand, NMC batteries, although offering greater energy density – translation: greater autonomy on a single charge – are more delicate. Charging to 100% can accelerate their aging due to the added stress on the materials, hence the recommendation to stop at 80% for everyday use.

The differences don’t stop there. The choice between LFP and NMC also influences the weight of the vehicle, its energy storage capacity, and even its cost. LFPs, with their lower energy density, are often less expensive and add less weight to the vehicle. The more expensive NMCs compensate with better performance in terms of autonomy.

Good charging practice depending on use

Why knowing your battery chemistry is essential

Knowing whether your car is equipped with an LFP or NMC battery allows you to charge it optimally, thereby extending its lifespan. An 80% daily charge for an NMC battery is ideal for most uses. But be careful, this rule has its exceptions.

Exceptions to the rule: long journeys and storage

Planning a long journey? Charging your NMC battery to 100% exceptionally is perfectly acceptable. The need for greater battery life outweighs the risk of accelerated battery aging. Likewise, if you plan not to use your car for several days, adjust the charge level according to the battery type to avoid degradation.

So, LFP or NMC?

The difference between these batteries should not be taken lightly when purchasing an electric car. Opting for a model equipped with an LFP or NMC battery should be an informed decision, considering the inherent advantages and disadvantages of each chemistry type.

LFP batteries, although less dense, offer increased stability and safety, while NMC batteries stand out for their ability to provide greater autonomy.

Moreover, battery technologies coexist in the same model: take the example of a Tesla Model 3 or Model Y, or a Volvo EX30, there is LFP and NMC.

Note that there is no “bad” choice per se, but rather a question of adequacy between the user’s priorities, their budget obviously and the characteristics of each type of battery.

In addition, the lack of perspective regarding the long-term performance of these technologies in various contexts adds a layer of complexity to this decision. Each chemistry has its strengths and weaknesses, influencing the performance, lifespan, and even the ecological footprint of the vehicle.

Besides, there are also other technologies besides LFP and NMC. And again, solid-state batteries are arriving and are a major technological advance in the world of lithium-ion batteries, and we recently devoted a complete file on what this allows for manufacturers.