Are Lithium batteries more cost affective than using lead acid batteries for electric vehicles?

Lead acid deep cycle marine batteries last up to 500 charge and discharge cycles of 50% (DOD) depth of discharge. About 300 cycles if discharged to 80% (DOD). Lithium batteries last up to 2000 charge and discharge cycles of 80% DOD, and up to 3000 charge and discharge cycles of 70% DOD.

Depending on the battery, the rated discharge is between 1C and 2C continuous. This means that the battery can only give so much power so fast in relation to its capacity.

If a batteries rated capacity is 100 Amp hours and the continuous discharge rate is 2C, then the battery can deliver 200 Amps (2 x 100 Ah) for one half an hour continuously. A prismatic Lithium 100 Ah battery rated at 3C should be able to put out 300 amps for one third of an hour.

A pack of 8 -100 Ah batteries connected in series at 3.2 Volts each equals 25.6 volts x 100 Ah. So a 24 volt device that uses 2400 watts discharging at 100 amps continuously will be "dead" in approximately one hour.

The 100 Ah Prismatic Lithium batteries will handle short bursts of 10C or 1000 amps without damage. A 100 Ah lead acid battery would be permanently damaged if discharged for even a few seconds at 1000 amps. The Lithium battery has about twice as much energy density per pound as the lead acid battery. The lithium battery will last 4 to 6 times as long as the lead acid battery so the total cost of ownership will be less. Think how much it will cost, or how much work it will be, to replace the lead acid batteries four to six times.

 Cost comparison

 Let's take the 6 volt Trojan deep cycle lead acid battery often used in conversions these days at $125.00 for 225 AH x 6 volts.

 These will last any where from 20,000 - 40,000 miles if you are nice to them and don't discharge them to below general safety zone so your batteries won't die after a couple weeks. With about half of that in useable energy due to Peukerts effect.

The lead acid battery roughly weighs about 8 times as much as Lithium battery and has about 6 volts x 100 AH to use safely, though you might see even less than this if you're pulling significant amperage.

The prismatic lithium batteries (Sky Energy) prices are $1.25/AH or $125.00 for a 3.2v nominal x 100 AH with roughly 90% of usable energy (safety voltage) and no Peukert effect so, two of them in series means a 6.4v x 100 AH battery with 90 AH useable for $250.00.

Roughly twice the price as lead acid with 1/4th the weight and lasting anywhere from 150,000-400,000 miles depending on storage temp, charge during storages, etc.

There are several examples of Lithium battery powered cars getting 100 miles of range on 10 kwh or so. I'm not aware that there are any lead acid cars even with 28 kwh+ that can get 50 miles of range.

If you start trying to gain range with lead acid batteries you need bigger motors and higher amperage controllers to pull the weight.  Lead acid batteries are a diminishing return.

Electric Vehicle Concepts has spent the last five years making comparison test with two identical Rixster roadsters. One powered with five twelve volt lead acid batteries and one using 26650 spiral lithium cells.

Both battery systems cost $1200. The lead acid charger cost $500 and the lithium charger was $100. Both chargers use 110 volt ac. The lithium battery car can charge in less than one third the time as the lead acid powered car.

The lead acid battery powered car lasted two years before needing battery replacement and the lithium powered car is still running the same batteries in the fifth year.

Electric Vehicle Concepts .com

Spherical Designs Organization

E-V Concepts

  Lead Acid vs Lithium