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The Battery Pack for Mitsubishi’s i MiEV

14 May 2008

Imiev1
The battery pack of the i MIEV. Click to enlarge.

At the Advanced Automotive Battery Conference and Symposium 2008 in Tampa, Florida (12-16 May), Takuha Miyashita from Mitsubishi described the characteristics of the lithium-ion battery pack that Mitsubishi, in partnership with GS Yuasa, developed for the i MiEV (earlier post).

The i MiEV is powered by a compact 47 kW motor that develops 180 Nm (133 lb-ft) of torque and a 330V, 16 kWh lithium-ion battery pack. Top speed is 130 kph (81 mph), with a range of up to 160 km (100 miles) under Japanese 10-15 cycle driving conditions.

GS Yuasa Corporation, Mitsubishi Corporation (MC) and Mitsubishi Motors Corporation (MMC) launched a joint venture—Lithium Energy Japan—last December to manufacture large-capacity and high-performance lithium-ion batteries. (Earlier post.)

Battery-maker GS Yuasa is the majority shareholder with 51%; MC holds 34% and MMC holds the remaining 15%. Initial production is targeted at 200,000 cells in fiscal year 2009.

The 16 kWh i MiEV battery pack is installed under the base floor. The pack consists of 22 cell modules connected in series at the nominal voltage of 330 V—the high voltage helps deliver high power. There are two types of modules to enable efficient use of the limited space. Two 4-cell modules are vertically placed at the center of the pack and 10 8-cell modules are placed horizontally.

Specifications of the i MiEV Li-Ion Cell
Dimensions 43.8W x 113.5H x 171D [mm]
Weight 1.7 kg
Rated capacity 50 Ah
Nominal voltage 3.7V
Specific energy 109 Wh/kg
Energy density 218 Wh/L
Specific power
(60-sec pulse at 25°C and 50% SOC)
550 W/kg
Max output current @ 25°C 300A

Mitsubishi and GS Yuasa developed the cell for both high specific energy and high rate discharge. The newly developed prismatic cell used in the i MiEV pack has a specific energy of 109 Wh/kg and specific power of 550 W/kg. Energy density is 218 Wh/L. The entire pack has a specific energy of 80 Wh/kg.

The cell—and pack—feature high capacity retention at constant current discharges. Capacity at the high current of 200A is slightly less than at the lower rates (93.9% of capacity).

When discharged with an ambient temperature of 25° C, the pack is capable of delivering the maximum power from 80% DOD. Even at 0°C, the pack can deliver the maximum power from 70% DOD and enough power for propulsion from 90% DOD.

Imiev2 Imiev3
Pack capacities at 25°C. Click to enlarge. 60-sec pulse power of pack. Click to enlarge.

Mitsubishi tested the cycle life of the pack under standard (50 A) and quick charge (120 A) conditions using the JC08 driving pattern and found that the pack retained 84% of capacity with quick charging and 83% with standard charging after 1,000 cycles.

Development of the i MiEV EV concept began in 2005, and Mitsubishi is currently field testing units in Japan in cooperation with electric utilities, with market introduction slated for 2010. The company is also targeting market introduction in Europe and North America.

May 14, 2008 in Batteries, Electric (Battery) | Permalink | Comments (42) | TrackBack (0)

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Comments

Looks like 2010 is shaping up to be the big year for plug-in vehicles. Not sure what could derail the mass selling of plug-in cars and trucks in 2010. But considering recent history, I will believe it only when I can BUY one and keep it.

All the new cars are great but what about the
retrofit market? I have 2 vehicles that are paid off
and in good condition.
Is anyone designing EV retrofits? Gas just hit 3.99 a gal this AM. I can see 5.00/gal which means an investment in NON gasoline alternatives can now be looked at.
Something like an older Saturn SL1 or any cars with lower curb weight seems like good candidates.

Initial production is targeted at 200,000 cells in fiscal year 2009.

Obviously a lie -- Dr. Anderman says industry-wide production won't reach this much even by 2012. How can a single battery maker produce this much in 2009? Do they really expect us to believe such wild claims? Dr. Anderman is never wrong!

BTW, the battery curve shows noticeable degradation up a 3% highway grade, but many long grades in the US west are 6%. Of course i-MiEV is more of an urban runabout so 3% may be a reasonable design parameter. I still wonder if a 60-80 mile real-world range will sell in the US, though.

BobT

Please check with MIRA (England) for ICE to PHEV retrofits

note that the scale on the left in the first graph only goes down to 250 V, not 0...

dog: LOL ... I can see that the "good" doctor is going to take flak for quite some time.

It seems that the total number of cells could be (2x4=8) + (10x8=80) = 88 and not 22, to get 330 Volts unless a step-up converter is used.

Regardless of the number of cells, this seems to be a workable power pack. It could power the new GM Volt-PHEV-40 and other similar PHEVs.

First generation PHEVs seems to be on the horizon for 2010/11.

Yes, it's 88 cells. Power density is less than the Volt spec. Cycle life may also be an issue.

Is this battery lithium-cobalt-oxide? Kind of scary.

In regards to MiEV climbing a steep grade slope, below is a link to the video.

Quote from a blog:
Unless I am interpreting the numbers incorrectly, it looks like the engineers take the iMiEV on a hill-climbing test run, from 663m (2,175 ft.) to 2,450m (8,038 ft.), a total vertical ascent of 1,787m (5,863 ft.) over a distance of 28.7km (18 miles).

Note:

Since I'm not allow to post links, please google the title: "iMiEV on display at Beijing Auto Show, climbs to summit in new video"

It has the link to the high quality video.

[Well, I tried to post information about iMiEV climbing up the hill, but kept on being rejected due to spam filter.]

Mitsubishi site has a video of iMiEV traveling up some mountain roads. It was described as a vertical ascent of 1,787m (5,863 ft.) over a distance of 28.7km (18 miles). All that is on one charge.

Another site mentioned that he thought it had recharge all the electricity used from gliding downhill. I'm not sure I see that in the video, but overall, I'm pretty impressed.

Maybe the GGC will release my previous comments, and you can follow the links... Otherwise, oh, well...

Looking forward to Mitsubishi releasing this little car here in the US. It would really be perfect for a City car (New York, Chicago etc.) and I hope they sell a ton of them. Unfortunately, the range and rear wheel drive means it won't be able to replace my commuter car here in the upper Midwest, although I'll still be seriously tempted..it is a cute little thing.

I have to take back my comment on the range, if Mitsu can really deliver 100 mile range (real driving conditions, like with the air conditioning or heat on), this could replace my commuting car (I'd probably grin and bear the rear wheel drive since I don't drive every day). Come on Mitsu, roll this thing out and get it over here in the US.

22 cell modules it says - so each module has 4 cells, probably with a common temperature sensor for the module. So 200,000 cells divided by 88 cells give us 2300 batteries per year.

anyone else think its strange that the battery retains its capacity longer with fast charge than with trickle charge?

100miles x 1000cycles= 100,000 miles til 83% capacity. This pack is probably good for ~160,000miles before it becomes unusable.

If the chemistry is indeed lithium cobalt oxide (not advanced chem) then it should tell us the EVs are workable NOW.

I doubt it is lithium cobalt if it is getting 1000 cycles in such an aggressive way... I wonder how many cycles you would get with shallow discharges?, lets say 10 miles daily.

That is a very heavy pack and a bloody large one too.

Alot of bev makers are squeaking into the 100 mile range as I expected they would by simply using absurd dod levels.. tho least this one isnt 100%.

Dont expect them to sell any more then they have to to make the various mandates as every one of these puppies is a big money loss and will likely require at least 1 pack replacement under warranty until they can improve the chem.

I only expect a few companies to realy try and push erevs and bevs and in the us all of them will wind up being made here due to the dollar and that locks these guys out for now unless they build plants in the us NOW.


It is the nature of Lithium cells to do a "shallow" discharge.

A single cell is fully charged at 4.2 volts and if you discharge them below 3.0 volts, you may not be able to recharge them again.

I understand the voltage characteristics of lithium cells.. by shallow discharge I meant only using 10-20% of the batterie's capacity instead of 80-100%.. that kind of usage would probably triple the life of the pack.. but the cells do age also, they may just die anyways in 3-10 years, even if you dont drive the car.

from a previous article they claimed 109wh/kg, or about 150kg for the 16kwh pack.. or equivalent to the weight of about 45 gallons of gas.

45 gallons of gas will be $200 soon :)

109Wh/kg is the cell itself.

The article states the entire pack is 80Wh/kg so closer to 200kg for the battery pack weight.

The state of the dollar will not fundamentally change the market dynamics of Lithium batteries. Asian battery makers would still be able to assemble batteries at a better price point compared to US battery makers.

The impact would likely be carried by the automakers. They would have to go with smaller batteries than they would like, if they still care about prices.

Remember the a123 batteries are 2/4td the weight and size snf they take up a huge space and are 160 kg after all the battery systems are counted. And we dont know the calander life of the cells.

As for making them in asia.. the dollar is already nuking profits and raising prices not to mention the fact oil is raising the cost of shipping...

Let's see... Too much good news here. Let's catastrophize about money for a while. Hey, itza job.

It will be a wonderful fad car for those who can afford it... but it likely over its life will eat 30 or more hybrid cars worth of packs... and be driven mostly by people who will still own hummers and highlanders... green all day black all night.

The development of mass manufacturing for EV batteries such as this one will dramatically reduce the cost of HEV and PHEV batteries, leading to a reduction in HEV cost and wider adoption of HEVs and PHEVs.

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