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Batteries: It’s not all about chemistry

01 July 2011

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Industry players in the battery market took center stage at the Electric Vehicles Land, Sea, Air Europe 2011 conference, held by IDTechEx in Stuttgart, Germany, on 28-29 June 2011. Their key message was that while the improvement of battery chemistries takes time, electronics and battery management systems can change fast and greatly improve battery performance, life and safety.
The global market of EVs is about to double in the next ten years.
Batteries are software controlled, which can be optimised to give full benefits of the battery to users. Software can improve the battery through cell isolation, quiescent recovery, cyclic redundancy, lossless cell balancing and variable power output.

The benefits of such optimisation can be summarised as follows:
  • Minimum increase in battery lifetime 30%
  • Increased battery capacity >14% (Depends on redundancy ratio)
  • Variable power control (Avoids need for and cost of external controllers)
  • Immunity to single cell failures (Gets you home)
  • Lossless cell balancing
  • More accurate SOC estimation
Rest periods while charging/discharging

Chemical action in the cell cannot take place instantaneously, and reactions can therefore take between several seconds to several hours to be completed. Longer reaction times are even more noticeable in large high capacity cells.

According to Mr Barrie Lawson, Chairman of CHEEVC, a start-up company dedicated to developing batteries for electric vehicles (EVs) and a range of applications, “the introduction of “rest periods” during charging and discharging allows more complete transformation of the active chemicals.”

Providing the time for the ion transportation to be completed and the chemical reactions to stabilise, reduces the stress on the cells and allows increased cycle life or increased instantaneous charge/discharge rates.

The cyclic redundancy is a process where one or many cells are bypassed while remaining cells carry the load. The bypassed cells have rest periods but can be switched in to provide a time limited power boost.

Battery Management Systems (BMS)

“Battery Management Systems (BMS) are key to ensure EV safety and connectivity with the grid”, said Tanji Adebusuyi, R&D, Lithium Balance. According to Mr. Adebusuyi, lithium-ion batteries are inherently unsafe unless properly managed. Therefore, BMS are needed to ensure safety and reliability, but also to improve performance through discharge rate control, regeneration, optimised charge algorithms and cell balancing.

Cell balancing is a way to ensure that all cells connected in series have the same State of Charge (SoC). This allows for the pack capacity to be maximised, and to extend pack longevity because battery life depends on the cell with the lowest capacity.

BMS exist for every battery type and every application, but different levels of requirements are needed, depending on the application. The requirements for an automotive grade BMS are quite extensive, including multi-level safety, software architecture, certification and warrantability.

The top 3 challenges in the future for BMS are:
  • To ensure safety and reliability
  • To achieve cost reduction without compromising safety
  • To integrate the battery in charging infrastructure
Electric Vehicles Land, Sea & Air USA 2011

IDTechEx will organise the Electric Vehicles Land, Sea & Air USA from 1-2 November 2011 in San Jose, California. This event will concentrate on potentially disruptive breakthroughs in the future, including radically new materials, components and forms.

This event will provide a platform for EV manufacturers to diversify, for components and subsystems suppliers to make their products available for as many vehicles as possible, and unlike other events, for electricity suppliers, regulators, analysts and investment experts to assess the whole market. Finally it will cover research efforts, challenges and future breakthroughs.


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