The EV Route

Charging

Why you should not charge to 100% on a journey

The most useful thing to understand about rapid charging is that the rate is not constant. It is highest when the battery is nearly empty and collapses as it fills — which means the fastest journey involves arriving at chargers low and leaving them early.

Updated 4 min read 13 citations

Electric saloon car parked at the roadside in Munich
AuHaidhausen · CC BY 4.0 · Wikimedia Commons
The shape of a rapid charging curve Charge rate is highest below about thirty per cent state of charge, falls steadily from forty per cent, and by eighty per cent has dropped to roughly a third of its peak, continuing to fall to almost nothing at a hundred per cent. 04080120160020406080100State of charge (%)Charge rate (kW)Charge rate80%
Why nobody charges to 100% on a journey. The taper is not a defect — it is the cell chemistry protecting itself as the anode fills. The last 20% typically takes as long as the first 50%, which is why two stops to 80% beat one stop to 100%. Illustrative shape typical of current CCS packs; peak power and taper points differ by vehicle.

What the taper actually is

A lithium-ion cell charges by moving lithium ions into the anode. When the anode is mostly empty they intercalate readily and the cell can accept very high current. As it fills, the process slows, and pushing current anyway risks plating metallic lithium on the anode surface — which is both a permanent capacity loss and a safety problem. The battery management system therefore reduces current as state of charge rises. That is the taper [1].

It is not a limitation of the charger. A 350 kW post and a 150 kW post deliver identical power to a car at 75% state of charge, because in both cases the car is asking for far less than either can supply. This is why headline charger power is a much weaker signal of journey speed than people assume, and why a queue at a 350 kW site can be slower than an empty 150 kW one.

What this means for planning

The practical consequence is counterintuitive: you should plan to arrive at chargers with a low battery. A car arriving at 10% and leaving at 80% has spent its entire stop in the efficient part of the curve. A car arriving at 45% and charging to 95% spends most of its stop in the slow part, and will take longer to add fewer kilometres.

It also means that on a long route, more stops can be faster than fewer. Two twenty-minute stops in the 10-80% band often add more range than one forty-five-minute stop that runs to 95%. The exception is when chargers are sparse enough that the next one is a genuine gamble, which is a coverage problem rather than a charging one.

Preconditioning

Cell temperature governs how much current a pack will accept, and a pack that has been sitting outside overnight in winter can be limited to a fraction of its warm-weather peak. Most modern EVs will heat the pack in anticipation of a rapid charge, but usually only if the charger is set as a destination in the car's own navigation — not a phone app running alongside it. This is the single most common reason a car charges far slower than its specification suggests.

Three-lane British motorway with traffic in both directions under a grey sky
Klaus with K · CC BY-SA 3.0 · Wikimedia Commons

Does rapid charging damage the battery?

Less than the folklore suggests, and less than calendar ageing does. Analyses of large fleets have generally found that heavy rapid-charging use is associated with measurable but modest additional degradation, and that time and average state of charge matter more [2]. The effect is real, and it is larger when charging a hot or very cold pack, but it is not a reason to avoid rapid charging on the journeys it exists for.

The more defensible caution is about habitual behaviour rather than journey behaviour: a car that lives at 100% state of charge in a warm climate is being treated worse than one that is rapid-charged on a long trip once a month. Our sister site covers the fleet evidence in more detail at <a href="https://chargingcompared.com/battery-health/">Charging Compared</a>.

Why did my car charge at 50 kW on a 350 kW charger?
Almost always state of charge or pack temperature. Above roughly 70% the car asks for far less than the post can supply; a cold pack does the same at any state of charge. Neither is a fault with the charger.
Should I wait for the battery to reach 100%?
On a journey, no. The last 20% typically takes about as long as the first 50%, so you are usually better off driving on and stopping again.
Is it bad to arrive at a charger nearly empty?
No — it is the efficient way to use one, because the whole session happens in the fast part of the curve. Arrive low at chargers you have reason to trust.
Does the taper differ between cars?
The peak power and the exact taper points differ considerably. The shape does not: high early, falling steeply past 60%, negligible near full.

References

Every citation below links to the original peer-reviewed record on PubMed or via DOI. Nothing here is a substitute for medical advice.

  1. Electric Vehicle (EV) Review: Bibliometric Analysis of Electric Vehicle Trend, Policy, Lithium-Ion Battery, Battery Management, Charging Infrastructure, Smart Charging, and Electric Vehicle-to-Everything (V2X) Veza I, Syaifuddin M, Idris M, et al. · Energies · 2024 · Journal article DOI
  2. Dynamic User Equilibrium for Electric Vehicle Departure Time and Path–Charging Choices with Wireless and Fast Charging Services Zhang X, Ren H · World Electric Vehicle Journal · 2026 · Journal article DOI
  3. Model Predictive Control Using an Artificial Neural Network for Fast-Charging Lithium-Ion Batteries Jaguemont J, Darwiche A, Bardé F · World Electric Vehicle Journal · 2025 · Journal article DOI
  4. Fast-Charging Model of Lithium Polymer Cells Jaguemont J, Bardé F · World Electric Vehicle Journal · 2025 · Journal article DOI
  5. Comparison of EV Fast Charging Protocols and Impact of Sinusoidal Half-Wave Fast Charging Methods on Lithium-Ion Cells Althurthi S, Rajashekara K, Debnath T · World Electric Vehicle Journal · 2024 · Journal article DOI
  6. An Implementation of Quasi-Newton Algorithm for Fast-charging Lithium-Ion Battery (LIB) Optimization in Electric Vehicle Application Anjarani M, Raharya N · International Journal of Electrical, Computer, and Biomedical Engineering · 2024 · Journal article DOI
  7. End-to-End Direct-Current-Based Extreme Fast Electric Vehicle Charging Infrastructure Using Lithium-Ion Battery Storage Powar V, Singh R · Batteries · 2023 · Journal article DOI
  8. Advancements in Electric Vehicle Charging Infrastructure: Fast Charging, Wireless Charging, and Smart Grid Integration Jordan Y. Arpilleda · International Journal of Advanced Research in Science, Communication and Technology · 2023 · Journal article DOI
  9. Novel Hybrid Thermal Management System for High-Power Lithium-Ion Module for Electric Vehicles: Fast Charging Applications Karimi D, Behi H, Van Mierlo J, et al. · World Electric Vehicle Journal · 2022 · Journal article DOI
  10. TEKNIK FAST CHARGING BATERAI LITHIUM-ION MENGGUNAKAN LOGIKA FUZZY Anshori A, Siswojo B, Hasanah R · Jurnal Ecotipe (Electronic, Control, Telecommunication, Information, and Power Engineering) · 2020 · Journal article DOI
  11. Bottlenecks to Fast Charging of Lithium-Ion-Insertion Cells for Electric Vehicles Chandrasekaran R · ECS Transactions · 2014 · Journal article DOI
  12. Bottlenecks to Fast Charging of Lithium-Ion-Insertion Cells for Electric Vehicles Chandrasekaran R · ECS Meeting Abstracts · 2013 · Journal article DOI
  13. Fast Charging Method Based on Estimation of Ion Concentrations using a Reduced Order of Electrochemical Thermal Model for Lithium Ion Polymer Battery Choe S, Li X, Xiao M · World Electric Vehicle Journal · 2013 · Journal article DOI