How To Ruin Your Electric Car's Battery - NMC Edition!

Summary

The video explains how to reduce degradation in NMC lithium-ion batteries, which use nickel, manganese, and cobalt oxides. Its central point is that heat, high state of charge, and repeatedly using a large portion of the battery’s capacity can accelerate aging.

The recommendations are intended to help a battery retain capacity over time, but the presenter emphasizes that they are not strict rules. Even with less-than-ideal habits, a battery may last for the life of the car.

Why batteries degrade

• Battery aging has multiple causes, but many degradation reactions happen faster when the battery is hot or at a high voltage, which generally corresponds to a higher state of charge.
• One example is the growth of the solid electrolyte interface (SEI) on anode particles and the cathode electrolyte interface (CEI) on cathode particles. These layers consume electrolyte, lithium, and other useful materials.
• Interface formation begins during the battery’s first charge. The presenter says this process accounts for roughly 10% of initial capacity loss during factory preparation; continued growth contributes to degradation over time.

Three practices to reduce degradation

1. Avoid storing the battery at 100% for long periods, especially in hot conditions.

   • High temperature and high state of charge together can cause substantial capacity loss.
   • In a study described in the video, batteries stored at 50°C and 100% charge lost capacity far faster than those stored at lower charge levels. A battery stored at 30% retained more capacity over a longer period.
   • Professor Jeff Dahn’s suggested target for long-term storage in a hot environment is about 30% charge. For long-term storage in cold conditions, a higher level, such as 70%, is presented as less concerning because reactions proceed more slowly.

2. When practical, recharge before the battery gets very low rather than routinely using a large share of its capacity.

   • The video calls this keeping the battery’s depth of discharge (DoD) relatively low. For example, using the battery between 60% and 40% is a smaller DoD than repeatedly going from 100% to 0%.
   • Lithium moving in and out of cathode crystals causes them to expand and contract. In conventional structures made up of many small crystals, differently oriented crystals change shape in different ways, which can cause cracking. Cracks allow further damaging reactions and consume useful battery materials.
   • Smaller charge-and-discharge ranges reduce this repeated expansion and contraction. The video describes a study in which frequent 0–100% cycling degraded capacity much faster than cycling within a narrow 40–60% range, even though the batteries delivered the same total energy.
   • Dahn’s suggested range is around 25% depth of discharge when convenient. A simple practical version is to plug in after trips rather than waiting for the battery to become low.
   • The trade-off is convenience: keeping to a very narrow range limits how much of the car’s range is available. The presenter says not to worry excessively about this.

3. Avoid regularly charging to 100%, particularly with some high-nickel NMC batteries.

   • Some higher-nickel cathodes have a voltage plateau near the top of charge, roughly from 75% to 100%. That region is associated with significant volume changes, which can contribute to cracking in multi-crystal cathodes.
   • Even with a single-crystal cathode—which reduces cracking—charging high-nickel batteries through this region can release a small amount of oxygen. The resulting gas formation can also contribute to degradation.
   • Dahn’s suggested everyday limit is about 75%. Charging to 100% the night before a long trip is reasonable when extra range is needed.
   • This advice is not universal: the video says lower-nickel NMC designs and lithium iron phosphate (LFP) batteries do not have the same concern to the same extent. Some vehicle designs also use single-crystal cathodes to reduce cracking.

Practical takeaway

• Follow the practices that are easy to fit into your routine, but prioritize the driving range and charging convenience you need.
• If charging at home is not available, repeatedly limiting charges to 75% may be inconvenient. The presenter’s practical advice is to charge only to a level that feels comfortable: a lower charge is generally gentler, but use 100% when you need it.
• The video says DC fast charging is typically not a major concern because the vehicle controls charging current to keep it within what the battery can handle.
• These habits are meant to maximize long-term capacity, not to suggest that occasional high charges, deep discharges, or fast charging will ruin a battery. The presenter notes that manufacturers design around degradation and that EV batteries generally have long warranties.

Speakers and sources featured

• Engineering Explained presenter — narrator and explainer.
• Professor Jeff Dahn — cited for battery-care recommendations and research expertise; the video also points viewers to a presentation by him.
• Battery-aging studies — unnamed studies discussed as evidence for the effects of storage temperature, state of charge, and depth of discharge.