Introduction

EV battery reliability is dependent on maximizing the number of charge/discharge cycles and minimizing capacity fade. 

EV batteries lose efficiency with a self-discharge rate exceeding 5% in 24 hours. Dropping below 80% capacity indicates the battery’s nearing replacement.

This can occur due to high-power DC fast charging that generates heat, accelerating degradation. Similarly, extreme temperatures during charging or storage can negatively impact cell chemistry. 

This is why understanding the impact of charging habits on EV battery reliability is important so that EV vehicles run on longer battery life. To achieve this, charging up to 80% or 90% capacity of the EV battery is recommended, and the intensity of fast charging must be slowed down. 

This article analyzes the impact of charging habits on EV battery reliability and suggests the best measures.

Some Evidence on the Importance of EV Battery Reliability

Several studies have been conducted that show how the charging habits affect the EV battery reliability of vehicles’ EV batteries. Some of these are as follows:

1. Study on the Nissan Leaf

This study, published in the eTransportation journal by Gao et al., 2024, investigated the impact of user behavior on electric vehicle (EV) battery reliability. The methodology was about the charging habits of 6,300 fleet and consumer EVs to identify factors influencing battery degradation. It focused on the effects of charging frequency, depth of discharge, and temperature on battery health.

Key Findings

• Charging Frequency: Frequent charging, particularly at high temperatures, accelerates battery degradation. This is because high temperatures increase chemical reactions within the battery cells that degrade the cell’s components.
• Depth of Discharge: Batteries frequently charged to 100% capacity experience faster degradation than those kept between 20% and 80% charged. This is because deep discharges and high depth of discharge (DOD) cause increased stress on the battery cells.
• Temperature: Batteries charged in hot temperatures show faster degradation than those charged in cooler temperatures, as heat causes unwanted chemical reactions. 

2. Study by Etxandi-Santolaya et al., 2024

This study analyzed various road types, charging behaviors, and EV models. It evaluated the key indicators related to speed, acceleration, driving times, and regenerative capabilities. These indicators were measured for different levels of degradation to quantify performance decay.

Key Findings:

• The impact of battery degradation is highly dependent on the road type and nominal battery capacity.
• Vehicles with long and medium ranges show good performance for common driving conditions.
• Short-range vehicles perform well in urban and rural road conditions, but on highways, they show speed and acceleration reductions of up to 6.7 km/h and 3.96 (km/h)/s, respectively.
• The study suggests that degradation should be fine for standard driving conditions as mid and long-range vehicles currently dominate the market.
• Additionally, the results helped define a functional End of Life criterion based on performance loss, which goes beyond the oversimplified 70–80% State-of-Health threshold.

3. Study by Isuzu Technical Center of America

The study utilized the GT-AutoLion tool, which is an electrochemical, physics-based simulation tool for modeling the electrochemical processes within Lithium-ion cells. Real-world battery information was collected from a light-duty Battery Electric Vehicle (BEV) Prototype at three milestones: Beginning of Test (BOT), 7500 miles, and 15000 miles.

Key Findings:

• The battery showed a degradation of 8.09% after a 7500-mile run.
• A more significant decrease to 10.42% of overall battery capacity was observed at 15000 miles.
• The battery model developed using the GT-AutoLion tool reflected the patterns of degradation observed in the real-world data.
• The degradation patterns generated by the model will be used to predict battery performance and improve range estimation for future Isuzu vehicles.

Some Patents on EV Battery Reliability

Let us go over the patents on extending the lifetime of EV batteries:

1. US20130221928A1 – Electric Vehicle Battery Lifetime Optimization Operational Mode:

This patent describes an operational mode that maximizes battery life by setting a low maximum allowable charge rate. This mode is designed to reduce battery degradation caused by high charge rates. 

The innovation lies in selecting operating and charging parameters that emphasize battery health. The patent falls under the classifications related to methods or circuit arrangements for monitoring or controlling batteries, specifically adapted for electric vehicles and for controlling battery temperature. 

The patent is currently active and assigned to Tesla, Inc., with an adjusted expiration date set for 2033.

Key Components:

• Thermal Management System: Maintains the battery pack within a range of temperature settings.
• Charging System: Allows the battery pack to be charged to various minimum and maximum states of charge (SOC) levels and at different charging rates.

2. US7622897B2 – Multi-Mode Charging System for an Electric Vehicle:

This patent is active and also assigned to Tesla, Inc., reflecting its importance in current electric vehicle technology and battery management systems. 

The innovation includes a system with multiple charging/operational modes from which the user may select. Each mode controls the cut-off voltage used during charging and the maintenance temperature of the battery pack. 

Based on the selected mode, the system aims to optimize either the vehicle’s performance or the battery pack’s longevity.

Key Components

• The system focuses on the methods of controlling the charging system and the operational parameters to optimize battery life.
• It includes claims on the apparatus for implementing the multi-mode charging system.

Top 3 Companies Working on EV Battery Reliability

Here are the three companies and their contributions to understanding the impact of charging habits on EV battery reliability:

Tesla, Inc.

• Patent Example: Tesla has developed a Battery Life mode within their vehicles that prioritizes battery health over performance.
• Contribution: Tesla’s approach involves sophisticated battery management systems (BMS) that adjust charging rates and thermal conditions to reduce stress and prolong battery life. Their patents also cover methods to optimize charging parameters, such as avoiding constant high-voltage charging, which can degrade battery health over time.

Ze Way SAS

• Patent Example: Ze Way SAS has patented BMS that contributes to smart charging strategies to encourage battery longevity based on usage patterns.
• Contribution: Their technology probably includes algorithms that learn from the user’s charging habits. The stations are equipped with machines that can charge multiple batteries simultaneously. Riders can swap their batteries within 60 seconds, ensuring minimal downtime and a swift continuation of their journey. Further, it adjusts the charging process to minimize battery degradation.

Fermata LLC

• Patent Example: Fermata LLC’s patents are centered around advanced charging infrastructure and management systems.
• Contribution: Here’s how Fermata improves EV battery charging:

• Vehicle-to-Everything (V2X) Charging: Their system allows EVs to get power from the grid. They can also send stored energy back to the grid (V2G), home (V2H), or building (V2B). This creates a two-way flow of energy.
• Grid Resilience: Fermata’s technology helps stabilize the power grid by enabling EVs to act as mobile energy sources. During peak demand periods, EVs can discharge stored energy, reducing strain on power plants and potentially lowering electricity costs.
• Smarter Charging: Fermata’s platform uses data and algorithms to optimize charging and discharging cycles. This helps to minimize reliance on fast charging, which can stress batteries, and prioritize slower charging methods that promote battery health.
• Revenue Opportunities: Fermata’s system allows EV owners and fleet operators to potentially generate revenue by selling excess energy stored in their EV batteries back to the grid during peak demand periods.

End Note

Improving EV battery reliability starts with understanding and focusing on charging habits. Tesla stands out among the evaluated companies because of its advanced patents that adjust charging speeds and temperature conditions to extend battery life.

Research and patent development should focus more on improving thermal management to keep batteries at optimal temperatures during charging. Also, it is highly recommended to educate users on best practices so that they opt for adaptive charging systems that learn and adapt to user habits.