Where we are

All five of the battery types discussed here are currently either used in electric vehicles or are planned to be used in those vehicles. Nearly all vehicles use lead acid batteries for starting up, and some of the original experimental electric vehicles used them as well. The most commonly used batteries in hybrids are NiCd in older ones, and NiMH in newer ones. The vehicles coming out in the next few years are likely to use Lithium Ion and most prototype cars use either Hydrogen or Lithium Ion batteries.

Below is a table displaying some key metrics for the current state of the five main types of batteries we have been talking about throughout this section.

Metric	Importance	Lead Acid	NiCd	NiMH	Lithium Ion	Hydrogen
Charge/Discharge Efficiency	% of energy entered vs. energy returned	70-92%	70-90%	66%	99.9%	up to 80%
Energy to Weight	Amount of energy stored per weight	30-40 Wh/kg	40-60 Wh/kg	30-80 Wh/kg	160 Wh/kg
Energy to Volume	Amount of energy stored per volume	60-75 Wh/L	50-150 Wh/L	140-300 Wh/L	270 Wh/L
Self-Discharge Rate	% energy lost over time	3-20%/month	10%/month	30%/month temp. dependent	None in "dumb" batteries, 5-10%/month in "smart"	None
Lifespan	Number of hours or cycles before battery loses 20% of it's capacity	500-800 cycles	2000 cycles	500-1000 cycles	1200 cycles or 24-36 months	5000 hours (150,000 miles)
Fast Charge Time	Time for a rapid charge	8 to 16 hours	1 hour	2 to 4 hours	1 hour or less
Energy to Cost	Amount of energy stored per dollar	7-18 Wh/$	Unknown	2.75 Wh/$	2.8-5 Wh/$
Toxicity	Harmfulness of components	Toxic lead and acids but fortunately, about 90% of lead acid car batteries are recycled	Cadmium is highly toxic and harmful to the environment	Relatively low toxicity, should be disposed of properly	Low toxicity	Low to no toxicity

For our sources, click on the the battery technology you are interested in: Lead Acid, NiCd, NiMH, Lithium Ion, Hydrogen.

For more information on the different battery technologies and where they are in terms of efficiency, power density, cost, toxicity, and lifespan, check out the table at http://www.batteryuniversity.com/partone-3.htm.