Using a souped-up version of a chemistry that's been around since the days of Edison, a Detroit-area startup wants to slash the costs of batteries for hybrids and plug-in cars.
Energy Power Systems (EPS) says it has boosted the power density and cycle life of the venerable lead-acid battery, without touching the low costs that made it desirable in the first place. With the new technology, batteries for mild hybrids and plug-in cars could cost less than half of what they do today, the company says.
Subhash Dhar, chairman, CEO, and founder of EPS, said in an interview:
The concept has always been to start with a chemistry that gives you high energy density, and then hope you can reduce the cost. But the industry has never made much progress in terms of cost. So we turned it upside down -- we started with low cost and improved the technology, so we can get the performance without disturbing the cost structure.
Energy Power Systems (EPS) proposes replacement of a 16-kWh lithium-ion battery, like the one in the Chevy Volt, with a 9-kWh lithium pack and a high-power, 3.5-kWh lead-acid pack. (Source: EPS)
In truth, the energy numbers of EPS' batteries are puny compared to that of today's lithium-ion batteries. Whereas, lithium-ion typically checks in around 150 Wh/kg, the EPS battery is 40 Wh/kg. But that doesn't worry Dhar. The EPS battery is not targeted at high energy (which translates to driving range in an EV), but is instead focused on power density. Power density is far more important for full hybrids, mild hybrids, and micro-hybrids, since those vehicles can extend their range by burning gasoline, Dhar told us. "When you realize that energy isn't critical, and power is critical, you can boost the power and not worry about disturbing the fundamental low-cost structure of lead-acid," he said.
That's why his company has lifted the power density of lead-acid from about 200 W/kg to 1,600 W/kg. Cycle life has similarly been improved by a factor of five.
I agree, Dennis. This doesn't look promising unless that are some technical breakthroughs to lower the cost of building the Volt. It doesn't look like high-volume consumer purchasing is going to save the day.
I suspect that the $40k retail price was chosen as the price they could eventually reach if development and volume go as per plan. Considering that the public has been reticent with $7500 off that number I think this will be a problem.
Mixing battery technologies seems to have the potential to reduce costs without hurting overall performance. Aren't marine deep-cycle batteries lead-acid ? The lead-acid seems like the answer to acceleration, while the lithium-ion is there for range.
Now this is a good engineering story. As we have debated hybrids and EVs, the issue has always been cost. The answer to the battery issue has always been lithium ion. This is not a technology I would embrace because of the cost.
By approaching the problem of cost rather than starting with a technology to apply, the EPS is solving the problem. I also like the hybrid lead acid and lithium ion idea. It is similar to a concept used in disk drives where a small solid state device is paired with a spinning drive to provide both speed and large storage at a lower cost.
I never thought I would hear about lead-acid batteries again. Traditionally, the chemistry isn't very finicky, but the cycle life is poor and the energy density is terrible. One bright spot in the chemistry is that the cells are easily recycled, with something like 97% of depleted cells being recycled.
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