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Argonne Tests EnerDel Li-Ion HEV Pack in a Prius

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.



77.41 mpg sounds extremely good. Is this with the new cycle? If it is, then this is a 70% increase in mpg (45->77mpg)

Its pretty good with the old cycle too, that would be a 28% increase (60->77mpg)

(although 45 and 60 are combined cycle numbers)

If this battery can provide the same cycle and calendar life as the OEM pack, I will petition Toyota to put this into Prius III :)).


Keep in mind the 77mpg was done with the battery at a higher initial SOC. I believe the Federal Urband Drive cycle is not the new EPA fuel economy listing but the old method used for CAFE purposes.


The way things are going lately I expect practical EVs within five years.


This is good real world testing. The fact that they can get 90 kW from this pack says that the 70 kW+ motor should be able to give more power to the car.


Previously, Idaho National Labs had confirmed in cell testing that an EnerDel system could produce approximately twice as much usable energy (90 kW)....

Should read twice as much power (90 kW).....

FWIW, I didn't think the Prius pack produced more than about 25 kW. The traction motor (MG2) is rated at 50 kW but that's because it can be powered from the battery and ICE (via MG1) simultaneously.

Hybrid fan

The first hybrids did their magic with, let's face it, a bunch of flashlight batteries. It's going to be fun to watch what they can do with a real battery pack.


Ahem.. there are a couple of mistakes here we should get corrected.
You said Twice as much usable energy (90kw)

You meant Twice as much usable POWER (90kw)

Well what power can the Prius use ?
At the moment the Prius battery delivers 100Amps @ 201v according to those who've put scanners on the ECU, although the Toyota literature quotes 21Kw which is close enough.
To this is added 30kw from MG1 (running at a constant 10,000rpm) from 12.5mph until 51mph.
So the traction motor MG2 is fully satisfied with 50kw all the way up to 51mph.

At this point MG1 must start slowing down because the ICE has maxxed out and the Toyota HSD internal gearing dictates this must happen.

MG1 output power consequently decays until at 100mph only 10Hp is generated for MG2, the 67Hp (50Kw) traction motor. However by this time the power reaching the wheels through direct mechanical connection from the engine has built to 66Hp, bypassing the electrical path entirely. Prius is a parallel/series hybrid so this should be no surprise.

It's not all bad news for MG2 which has been benefitting from the full 28Hp (21kw) supplied from the battery since passing thru' 20mph.

But there's a new problem on the horizon. Since the high voltage bus maxes out at 500v at 51mph, this voltage can no longer increase in consort with applied frequency. Obviously the threephase power frequency must keep be increased to make MG2 run faster to help push the car forward. While this voltage was able to increase with frequency this at least helped preserve torque proportional to motor current. Torque will now decline rapidly as the stator inductance will present rising impedance with frequency making it harder to force current through the machine.
The fact that power is reducing from MG1 anyway at this point onwards makes this a marriage made in heaven !
With this in mind it is doubtful, using this more powerful battery, whether the motor could absorb more than the 38Hp it currently absorbs as it hits 100mph.

I would say that MG2 would need to be upgraded just as they did in the Hybrid Camry if the full use of this 90kw battery is to be taken.

To use this new LI-ion battery they need to quarter its size to 22.5KW capability for equivalency, the text said to halve it.

Regarding energy storage it is 1.1kwh compared to the Prius' 1.3Kwh but text says that is not a disadvantage if 10-90% available rather than 40-80% of the NIMh. WOW some optimists here ! Of course when you're installing into 240,000 vehicles per year I think that that 10-90% figure will hopefully be buried with the hype.

The Prius as I have said ad nauseum is not an "electric car" but a vehicle with an electric transmission so the Kwh is not important. 1.1Kwh would still provide a useful 500% buffer against aging and cold temperature effects.

What this battery could do for the Prius is to double the regen braking capability allowing reduced brake wear even with spirited driving. The ability to absorb 100amps or more instead of the current 50amps would certainly be useful.

Finally (2nd error) they only mention a 1.1kwh device then what battery did they use for PHEV testing ?


From the EnerDel press release:
"The EnerDel battery pack, which is based on the company's unique lithium-titanate chemistry, avoided overheating during the test..."

My, that is quite an accomplishment! (sarcasm)

More seriously, though, it is important to note that they are testing a 1kWh LMO-LTO cell. They admit this isn't the desired chemistry for a PHEV application, given the low energy density. 1kWh is the size of the battery they made, even though it's clearly not well-suited for the application. So, what's the point of trumpeting this so-called "news"? This is a veritable fruitbasket of apples and oranges and the timing seems designed to help with their reverse stock split.


As this is the chemistry similar to AltairNano, and is demonstrated at an early development phase - it may be they're looking to ride the Altair wave. But, battery progress is clearly being made at a rapid pace and we wish EnerDel and their customers every success.


Hi All,

I think they are trying to sell this battery in place of the HEV NiMH battery. Ni prices have gone way up, and they may be able to be cost competitive as a result.

The problem in the real world (except metro Chicagoland where I live) is that downhill energy recovery is very limited in the Prius. So, besides the power they really need to double the capacity. People in Connecticut, the Ozarks and San Fransico would see a great boost in fuel economy with such a battery.

I must agree with those who point out how the current Prius design limits the advantages of a more powerful lithium ion battery. But, since the next generation will not be limited to that degree, the lithium battery will indeed produce remarkable improvement. It would be nice if Hymotion had a conversion kit ready when the next generation Prius goes on sale in early 2009.

John Taylor

The Toyota Prius has became the default and standard "test bed" for giving real world experience to various new battery chemistries.

It does lend a great deal of credibility to the testing, and we get a very good measure of confidence in real improvements.

@ T2 ... tks for the great explanation of why they didn't bother to use a pack of equal size and weight but double the range capacity.

Soon I hope to see an all electric car available as a new "standard test bed" for batteries. ... can we say 'Tesla' ...


since the next gen not limited to that degree.....

Toyota is tightlipped other than 1.8L engine which I'm having a hard time believing since there are better ways to go. I am interested in MG2 being upsized by either increasing the final gear ratio from its present 4.113 OR by increasing MG2's stack length. Inquiring minds wish to know, if you can share at this quiet spot in hybrid discussion ???


Why has no one wanted the battery except TH!NK? if it is so good!?

ross erwin

Has anyone considered the fact that the United Nations holds all the cards in the matter of lithium transport?
And I don't mean just to the manufacturer. Transporting a load of cars with Li batteries or just popping over to the store in your own Li electric would be considered transporting lithium.

leila asgari

I work in R&D of IRAN KHODRO as electrical expert .
We want to determinate HEV in IRAN KHODRO .

Would you help us ?

Best Regards
Leila Asgari

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