Testing of EnerDel’s 1.1 kWh lithium-ion pack for hybrid electric vehicles (HEV) (earlier post) by the Center for Transportation Research of Illinois-based Argonne National Laboratory corroborated the company’s earlier claims of energy; power and efficiency; and thermal performance, according to the company.
EnerDel integrated its battery system into a Toyota Prius, with no material modifications made to the Prius other than the integration of the battery system. EnerDel’s choice of active materials for its HEV cell is LiMn2O4 - spinel (LMO) for the cathode and Li4Ti5O12 (LTO, lithium titanate) for the anode.
Argonne ran HEV tests on the EnerDel pack, comparing it to the NiMH OEM pack, as well as a standard Plug-In Hybrid Electric Vehicle (PHEV) test designed to explore the capabilities of the EnerDel pack’s wider state of charge (SOC) window—approximately 10% to 90%, compared to approximately 40% - 80% on the OEM NiMH pack.
Previously, Idaho National Labs had confirmed in cell testing that an EnerDel system could produce approximately twice as much usable energy (90 kW) as the Prius’ NiMH battery pack. As a result, the EnerDel battery can be reduced to about half the size and half the weight of a NiMH battery with the same power performance. Moreover, EnerDel expects its pack to cost significantly less than a NiMH battery with similar performance characteristics.
Operating in the test Prius, the Li-ion results showed that there was a 67% reduction in internal resistance. More charge is delivered to and from the battery, increasing range and reducing heat and wasted energy. In the testing in the Prius, the EnerDel Li-ion pack was only air-cooled.
In the Plug-In Hybrid Electric Vehicle (PHEV) configuration (which allowed the testers to bring the battery to a higher state of initial charge than the HEV tests, reflecting the larger SOC window), EnerDel was able to achieve 77.41 mpg US over a Federal urban drive cycle. In the future, the size of the battery as well as an extension of the electric range could be increased to improve miles per gallon fuel economy.
(The LMO/LTO power cell is likely not EnerDel’s chemistry of choice for PHEVs—that application is more likely to be handled by the company’s Hard Carbon chemistry, as being applied in the TH!NK City battery electric vehicle. The Argonne testing of the LMO/LTO pack in PHEV configuration was designed to establish a performance baseline.)
The results open up two main vehicle design opportunities for potential customers, said EnerDel executives in a conference call discussing the results.
The first is to not change existing hybrid vehicle design specs, and to package EnerDel cells in a pack that is half the size and weight of a NiMH pack while achieving the same performance.
The second is to look at applying a standard HEV powertrain, with the same volume and mass, to a wider range of vehicles, since the battery has “upside” in terms of capacity. By being able to apply the same powertrain across a wider range of vehicles, OEMs could achieve larger efficiencies of scale, EnerDel suggested.