EV Engineering & Infrastructure

  • News
  • Articles
  • Batteries
  • Charging
    • Wireless Charging
    • Vehicle-to-Grid (V2G)
  • Electrification
  • Testing and Safety
  • R&D
  • Learn
    • Learning Center
    • Tech Toolboxes
    • Webinars
  • Resources
    • Digital Editions
    • Diversity & Inclusion
  • Advertise
  • Subscribe

How do uneven temperatures in battery packs affect performance?

By Rakesh Kumar PhD | October 31, 2023

Uneven temperatures within a battery pack can negatively affect its performance, longevity, and efficiency. Having all the cells at almost the same operating temperature is necessary for properly charging and discharging the battery pack in an electric vehicle (EV) or energy storage system. Some of the most prominent effects of uneven cell temperatures are reduced capacity, faster degradation, and safety concerns.

Figure 1 shows how the charge capacity of some rechargeable batteries changes with temperature when current is fed into them and then discharged.

Figure 1. The temperature versus charge capacity of different battery chemistries. (Image: IEEE Access)

Depending on the energy and temperature, a battery will respond differently. Therefore, the battery works well when the temperature is within the range given. If you don’t, the battery could get damaged, leading to thermal runaway. 

Figure 2 shows how temperature affects the operating range of a battery. 

Figure 2. A battery’s operating range during the charging and discharging process. (Image: Elsevier)

As shown in Figure 2, when the temperature reaches below 15° C, the battery charging process becomes sluggish. This is bothersome, particularly in cold regions and during the winter season. On the other hand, when the temperature reaches more than 35° C, the battery life is reduced due to faster battery degradation.

One of the most direct and immediate effects of uneven temperatures in a battery pack is reduced capacity. Lithium-ion batteries, commonly used in EVs and many consumer electronics, have a temperature-dependent capacity. Lower temperatures reduce capacity, while higher temperatures can improve it slightly. However, it’s important to ensure the higher temperature is still within the operating range.

Temperature imbalances can cause uneven aging and degradation within a battery pack. Lithium-ion batteries degrade over time, and temperature plays a crucial role in this process. Cells that operate at higher temperatures tend to degrade more quickly than those at lower temperatures.

Safety is another concern due to uneven cell temperatures, particularly in high-energy applications like EVs. Lithium-ion batteries can become thermally unstable when exposed to notable variations in cell temperatures. Thermal runaway is a self-perpetuating process that can result from overheating and cause fires or explosions.

High-temperature variations in battery cells can reduce their ability to accept a fast charge. This limitation is mainly due to the risk of overheating and thermal runaway. As a result, when some cells in a pack are significantly warmer than others, the entire pack’s ability to accept fast charging is limited.

Case study
Scientists at Xi’an Jiaotong University’s School of Energy and Power Engineering have noticed some interesting things about how cells are linked in parallel. Different temperatures in battery packs have been seen to cause particular patterns of uneven aging and discharge. 

In the beginning stages of the discharging process, wherever the cell temperature is high, a larger current runs. The period before 75% of the depth of discharge (DOD) constitutes the early stages of the discharging process. Upon reaching the turning point of the battery pack output voltage, the discharging current for the heated cells gradually drops. At this point, the cooler cells experience an increase in discharging current.

As the discharging process reaches 90% DOD, the discharging current behaves like it did at the start. In other words, the discharging current flow through the cell reduces when the temperature is low and increases when the temperature is high. 

When it comes to battery capacity, the rate of capacity loss goes up as the temperature difference between the cells goes up. The capacity loss rate of the battery pack also goes up as the working temperature of the cell goes up.

Summary
Cell temperature imbalances in high-energy systems like electric vehicles can pose problems such as reduced battery capacity, battery degradation, thermal runaway, limited fast charging capability, and battery aging. Operating the cell and the battery pack within a given temperature range is necessary. For the same purpose, a dedicated battery management system can be used.

References

  • A review on electrical and mechanical performance parameters in lithium-ion battery packs, Elsevier
  • State-of-the-Art and Energy Management System of Lithium-Ion Batteries in Electric Vehicle Applications: Issues and Recommendations, IEEE Access
  • Unbalanced discharging and aging due to temperature differences among the cells in a lithium-ion battery pack with parallel combination, Elsevier

Images

  • Figure 1, IEEE Access, Page 11, Figure 21
  • Figure 2, Elsevier, Page 14, Figure 23

 

 

 

 

 

You Might Also Like


Filed Under: Batteries, FAQs
Tagged With: battery, FAQ
 

Next Article

← Previous Article
Next Article →


 
“ee
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for EV professionals.

Featured Contributions

  • What role do thermal interface materials (TIMs) play in EV battery systems?
  • How evolving demands are driving innovations in EV battery safety and materials
  • How large EV battery packs can be safely recycled without disassembly
  • Changing from traditional powertrains to electrified machines requires optimizing the hydraulic system components to reduce energy consumption and extend vehicle range. What factors impact electric vehicle system design?
  • How to safely detect minute physical Li-ion battery flaws
More Featured Contributions

EE TECH TOOLBOX

“ee
Tech Toolbox: Internet of Things
Explore practical strategies for minimizing attack surfaces, managing memory efficiently, and securing firmware. Download now to ensure your IoT implementations remain secure, efficient, and future-ready.

Learning Center

EE Learning Center
Search Millions of Parts from Thousands of Suppliers.

Search Now!
design fast globle

Sponsored Content

  • Converting custom materials for EV applications
  • Advantech Powers Versatile Electric Vehicle Charging Systems

EV Training Days

ev
EV Engineering & Infrastructure
  • 5G Technology
  • Analog IC Tips
  • Battery Power Tips
  • Connector Tips
  • Design Fast
  • EDABoard Forums
  • Electro-Tech-Online Forums
  • Engineer’s Garage
  • Microcontroller Tips
  • Power Electronic Tips
  • Sensor Tips
  • Test and Measurement Tips
  • Contact Us

Copyright © 2025 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy | Advertising | About Us

Search EV Engineering & Infrastructure

  • News
  • Articles
  • Batteries
  • Charging
    • Wireless Charging
    • Vehicle-to-Grid (V2G)
  • Electrification
  • Testing and Safety
  • R&D
  • Learn
    • Learning Center
    • Tech Toolboxes
    • Webinars
  • Resources
    • Digital Editions
    • Diversity & Inclusion
  • Advertise
  • Subscribe
We use cookies to personalize content and ads, to provide social media features and to analyze our traffic. We also share information about your use of our site with our social media, advertising and analytics partners who may combine it with other information that you’ve provided to them or that they’ve collected from your use of their services. You consent to our cookies if you continue to use this website.OkNoRead more