Sunday, September 21, 2008

LiFePO4 batteries: A breakthrough for electronic vehicles

source: http://www.metaefficient.com/rechargeable-batteries/innovative-lifepo4-batteries-electric-vehicles.html

Soon, we’ll probably be seeing Lithium Iron Phosphate (LiFePO4) batteries being used in most electric cars and bikes. This new battery type is set to dominate the market. Based upon lithium ion technology, LiFePO4 batteries offer many advantages over lithium cobalt dioxide (LiCoO2) batteries which are commonly used in laptops, mp3 players and cell phones.

In electric vehicles, LiFePO4 batteries offer greater range, power and safety. They provide full power until they are completely discharged, and recharge in just 2.5 hours. LiFePO4 chemistry is also environmentally friendly — it’s the least toxic of all the battery types.

A Graph Showing The Different Power Capacities and Weight of Various Batteries Types

A Graph Showing The Energy Density Of Various Batteries Types

LiFePO4 batteries were developed by Dr. John Goodenough at the University of Texas. These batteries have seen wide acceptance recently in Asian countries, but still have not made inroads in the U. S. marketplace. However, you can find these batteries being sold on eBay for electric bikes and scooters. You can now get a 52V LiFePo4 battery for an electric bike, that will give you a 65 mile range on a single charge with 60A drain rate.

For electric vehicles and plug-in electric cars, the LiFePO4 batteries will typically perform well in temperatures up to 400-degrees F, last for 6 to 7 years at a charge-discharge cycle of over 3,000.

The biggest player in the LiFePO4 marketplace for electric vehicles, however, is A123 Systems that has teamed up with GM to develop these batteries for the Chevy Volt plug-in hybrid. Another big player is Lithium Technology Corporation who has been working with GM, Toyota and U. C. Davis to develop LiFePO4 batteries for all-electric and hybrid vehicles.

Here’s a list of all the advantages of LiFePo4 batteries:

  • Safe technology — will not catch fire or explode with overcharge
  • Over 2000 discharge cycles life compared to typically around 300 for lead acid
  • Double the usable capacity of similar amp hour lead acid batteries
  • Virtually flat discharge curve means maximum power available until fully discharged (no “voltage sag” as with lead acid batteries)
  • High discharge rate capability, 10C continuous, 20C pulse discharge
  • Unlike lead acid batteries, can be left in a partially discharged state for extended periods without causing permanent damage
  • Extremely low self discharge rate (unlike lead acid which will go flat quite quickly if left sitting for long periods)
  • Does not suffer from “thermal runaway”
  • Can be used safely in high ambient temperatures of up to 60C without any degradation in performance
  • Maintenance free for the life of the battery
  • Can be operated in any orientation
  • Does not contain any toxic heavy metals such as lead, cadmium, nor any corrosive acids or alkalies thus making LiFePO4 batteries the most environmentally friendly battery chemistry available
  • LiFePO4 cells are of solid construction — there are no fragile/brittle plates made of lead which can be prone to failure over time as a result of vibration
  • Can be safely rapidly recharged — when fully discharged can be brought to a state of over 90% fully charged in 15 minutes

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