I figure the amortized battery replacement cost is still more than the electricity cost for BEVs. Personally, I think this is what has held back so many big auto manufacturers like Toyota from moving beyond the current HEV design. If a RE-EV or full BEV discharges the batteries to a DOD that is too low, then that will shorten the battery life so much that the TCO will increase because the batteries will need replacement sooner (and they are not cheep yet.)

Comments?

Battery life is a complex subject that seems to depend on the DOD (depth of discharge), rate of discharge, rate of charge, management of heat in the pack, and battery chemistry.

About five years ago, a friend of mine and I both bought laptops at the same time. The batteries were Li-Ion and had about a 2 hour life. Within six months, the battery life dropped to about 45 minutes or less. A replacement battery was $150 and the situation was depressing.

   Both of us purchased new laptops about three years ago and neither of us has had any problem with the battery. The battery technology is still Li-Ion and our usage pattern is about the same. So why the difference?

   The only thing I can think of is that they either changed the charging method or the battery chemistry. But this is an amazing improvement.

   I was reading about battery technologies and energy density. The article was claiming that Li-Ion was popular because it has a very high energy density, perhaps 160 WH/Kg. But more interesting was that for the Volt batteries, they had decided to go for a technology with lower energy density but longer cycle life. These technologies are

    A123 Lithium iron phosphate
   LG Chem Lithium-manganese spinel

So if the new Lithium technologies have much longer life than the Li-Ion, then perhaps the Total Cost Of Ownership (TCO) will be lower. Perhaps the batteries will outlive the car.

   Another interesting datapoint is the NiMH batteries in the Toyota RAV4 EV. These cars are approaching 10 years in age and 100,000 miles. Apparently the battery packs are still running fine. It is a good thing because the batteries are not manufactured anymore and so they cannot be replaced.

   It will be interesting to see if battery packs can be made to last 150,000 miles and 10 years. If that can be done I think this will all become a non-issue.

John,

Yes, those RAV4 EV batteries are amazing, aren't they. Somewhere I read that Panasonic totally over-engineered them, to a cost prohibitive point. Since nickel price surged starting early 2006, and since LiIon batteries are more developed now, perhaps we will never really know if NiMH could be viable for mass production. But it is intriguing that Nickel prices have come down since its peak in mid 2007.

But since LiIon is here to stay, we are good, unless Li prices increase...

WOW, commodities prices are amazing. Nickel is down to 1/3rd of its peak price. It is scary to make long-term plans based on materials that have such fluctuations in commodities pricing.

But I think the pricing of the batteries show why GM's approach with the Volt is a good compromise. Why carry around a battery that will drive you 240 miles when a 40 mile battery will work most of the time. The small battery is 1/6th the cost, saves on weigh, saves on materials, replacement cost (if needed), recycling costs, etc.

   The 40 mile battery can make you, perhaps, 90% free of gasoline at a fraction of the price of the 240 mile battery.

    Of course, if battery prices drop dramatically in the future, then GM would have to revise the E-REV concept.

    The only other possible winning concept that I see is Aptera. By making the car highly efficient, they can use only a 10KWH battery (compared with the Volt's 16KWH) and still get a 120 mile range. So Aptera has made the all electric solution affordable by using efficiency. Of course, it is a strange 2 person vehicle. But I would drive one.

As John pointed out, the Rav4EV batteries are lasting the life of the cars - even with astonishing DOD "abuse."

We have private cars with over 150,000 miles on them. There have been two cases of pack replacement that I'm aware of - and in both cases the amortization of those batteries has proven to still return a lower cost of ownership than a comparable gas car would have had. (The replacements were not new batteries btw - only refurbished available.)

Darell,

The RAV4 EV is awesome for sure. I see Buy it Now prices of $50k for the car on ebaY. There is a guy in Reno who is putting (or has put) the Rav4 EV batteries into his s-10 truck: http://www.evalbum.com/1103. But I do wonder if Bill was able to get it to work...

Tom

I hear lots of talk changing batteries in the production EVs, and yet know of nobody who's actually managed to do it successfully. home-brew vehicles are one thing, but the production ones are entirely different animals. I'm a bit surprised to hear that somebody would try to use Rav batteries in the Ranger when the Ranger NiMH batteries are (at least were) a bit easier to come by.

Actually, it is an Electricar (Chevy S-10) "conversion".

Ah! That makes some more sense. :)