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Saturday, August 6, 2011

Electric Car Batteries: Lead or Lithium?

electric car batteries 1Which electric car batteries do you need for your conversion or NEV? Let's wade through the information and misinformation about electric car batteries for a minute, and you can decide for yourself what batteries you want. There are good arguments on all sides.
I keep hearing really smart-sounding guys on the discussion lists and forums say that you'll never have a really good electric car until lithium batteries become available. The major automakers keep saying that they'd offer electric cars if they could get a better battery. They make it sound like lead batteries are only good for grandma's golf cart.

electric car batteries 2In "Build Your Own Electric Vehicle",Seth Leitman says lead-acid batterieswork just fine for an electric car."Contrary to those who say you'll need a different type of battery before EVs are suitable at all," he writes, "today's conventional lead-acid batteries of the deep-discharge variety are perfectly adequate for your EV conversion." (p.177)
What? Lead batteries are the best electric car batteries for the money? Let's find out.

What's good about lead(acid) EV batteries?

  • They're cheap(ish).
    A 120v system will need 20 6v batteries, and they'll cost you 100-150 USD each; that's 2K-3K. If you splurge and get the best AGM battery technology money can buy, it still isn't going to cost you more than 5K for a lead-acid battery pack. If you treat them right, they'll last several years. Lithium? You'd better have an extra 16-20K to spend on your conversion.
  • They're available everywhere.
    You can get your lead acid batteries locally from a golf cart battery dealer, which saves you the shipping costs. Batteries are heavy and contain metals that are usually toxic, one way or another, and that translates into expensive shipping.
    • They're peppy.
      You can get on the freeway, you can race, you can get liftoff with lead acid electric car batteries; ) There's no reason that lead is any less of a car-propellant than lithium. The only thing that lithium offers, with all its expense, is that it weighs less. (Okay, okay, and lithium has more cycle lives. Theoretically.)
    • They're safe.
      Setting aside the issue of high-voltage safety practices for a minute, lead acid batteries are relatively safe no matter what you do to them. They can leak sulfuric acid in a crash, they can vent flammable gases when they are charged, but they are generally considered to be pretty safe batteries.
      Lithium has a reputation for being a little more excitable; maybe you've seen the laptop batteries bursting into flames on the barbecue videos? it's important to keep a careful eye on them to make sure they're not shorting or overcharging. LiFePO4, or lithium iron phosphate, are considered to be safe electric car batteries.

    What's NOT so good about lead electric car batteries?

    electric car batteries 3
    • They're heavy.
      That's it, really. All the other things you've heard pretty much boil down to this. When you hear about lead's lower energy density than other battery chemistries like lithium, it's easy for our brain to form a picture of a SLUG that can barely get away from a stoplight at 2 mph before it needs a charge again, but that's not reality. The energy density issue only means that an adequate number of batteries will weigh more.What this means in practice is that you'll need to choose between extra batteries or the ability to carry more passengers. If my observations of freeway traffic are any indication, you didn't really want the passengers anyway.
    • Fewer cycle lives.
      They don't have the same number of theoretical cycle lives as other battery chemistries. I say theoretical because cycle lives depend on your application, and...dirty little matter what kind of battery you've got, "battricide" happens quite a bit (that means human error - charging? Temperature? Too deep discharge, too often? - causing premature battery death; ).

    And what do our NEDRA electric drag racers say about electric car batteries?

    electric car batteries 4Their cars say "lead". Mike Willmon, current president of NEDRA, put deep-cycle lead acid (Hawker 12v) batteries in his "El Pinto Loco". John Wayland, owner of the "White Zombie", also uses Hawker 12v batteries. Rod Wilde uses Exide 12v in his "Gone Postal" racing van.

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