The Current State of Electric Vehicles Part 1: Electric Vehicle Battery Basics
Written on 05 October 2014
by Ruth Fisher, PhD
A copy of the full analysis can be downloaded by clicking on the link at the bottom of this blog entry.
The following are the essential factors at issue when considering batteries for use in powering electric vehicles:
Amount of Energy that Can Be Stored
The batteries of any given size that are able to store the greatest amount of energy in terms of both weight (specific energy) and volume (energy density) of the battery are the most desirable (efficient) to power electric vehicles. Perhaps the largest current disadvantage in terms of the state of battery development for electric vehicles (EVs) is the fact that currently EVs cannot go very far without having to have the battery recharged, creating so-called range anxiety. Lower battery range would be less of a problem if (i) there were more fueling stations around (currently there are very few refueling stations), and/or (ii) it didn’t takes so long to recharge the battery (20 minutes to several hours, depending upon the technology of the charger). Currently, EV manufacturers are working fiercely to increase both the specific energy and/or energy density of batteries for EVs so as to achieve greater vehicle range.
Each time a battery charges and discharges (runs through a cycle), it degrades a bit, which means the battery has a limited cycle life, after which point it is unable to operate adequately. The cycle life of a battery is distinct from its calendar life. Batteries degrade as they are stored, where the amount of degradation during storage depends on (i) the extent to which the battery is fully charged (the state of charge) while it is being stored, where batteries with less charge degrade more quickly, and (ii) the temperature at which the battery is stored, where batteries stored in more extreme temperatures degrade more quickly. Currently, the life of Tesla’s batteries are about half a dozen years, much less than the standard 20 year life of traditional internal combustion engine (ICE) vehicles.
The cost of manufacturing batteries for electric vehicles are substantially greater than those for ICE vehicles. Furthermore, the cost of the battery represents a significant portion (roughly half) of the total costs of manufacturing an electric vehicle. The cost of the battery must therefore be low enough that electric vehicles can compete with traditional vehicles. Battery costs have been reduced substantially over the past several years, from about $750 - $1,000/kWh just a few years ago to about $200/kWh -$400/kWh currently. However pundits generally agree that battery costs must be reduced to about $100/kWh - $150/kWh to be competitive with ICE vehicles.
The materials from which batteries are manufactured are both unstable and flammable. Batteries must therefore be carefully constructed to minimize the chance that the batteries will catch on fire.