Germany steering towards electric vehicles
17 June 2011
Welcome to the decade of hybrid electric vehicles
30 June 2011
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
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
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.