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GM engineers altered the lithium-ion battery packs chemistry to improve performance

The Chevrolet Volt, everyone's favorite "green" whipping boy, is getting a range boost for the 2013 model year. General Motors announced today that the battery-only range of the Volt would increase from 35 miles to 38 miles. The total driving range of the 2013 Volt including extended range operation (which taps into the gasoline engine/generator) now stands at 380 miles.
 
The miles per gallon equivalent (MPGe) increases from 94 MPGe to 98 MPGe.
 
GM says that it was able to improve battery performance of the Volt by altering the chemical composition of the battery and upping total battery storage capacity from 16 kWh to 16.5 kWh.


2013 Chevrolt Volt [Image Source: GM]
 
“The best way to explain what we’ve done at the cell level is to compare it to a cake batter recipe.  Sometimes if you use more sugar and less vanilla you get a better tasting cake. We’ve done some work at the cell level to modify the ‘ingredients’ to make a better end result,” said Bill Wallace, GM's director of Global Battery Systems Engineering. “This attention to detail will allow our customers to experience more pure EV range, which is the true benefit of owning a Volt.”
 
Yesterday, Honda announced that its lease-only Fit EV has a battery range of 82 miles and is rated at 118 MPGe.


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same
By Shadowmaster625 on 6/7/12, Rating: 0
RE: same
By Solandri on 6/7/2012 2:38:28 PM , Rating: 1
The Volt only uses half the battery's capacity. It was a 16 kWh battery, but only 8 kWh of it was used. So a bump up to 16.5 kWh could allow a bump up to 8.5 kWh usable, a 6% increase from 8 kWh. That's pretty close to the 8% range increase (roundoff error in the mileage probably accounts for the difference).

The reason you don't want to use the battery's full capacity is because deep-cycling (fully charging/discharging) certain types of batteries reduces their endurance. e.g. After a hundred or so deep cycles, they're at 75% original capacity, and after a few hundred deep cycles they're dead. You've probably seen these on old laptops - where you can charge the battery for 3 hours and it lasts 15 minutes. To prevent this, you use the middle charge capacity of the battery, never fully charging it, never fully discharging it.

Using just 50% of the battery's capacity as the Volt does is pretty conservative. The Prius also uses about 50%, but it's a much smaller battery (about 1.3 kWh) so sees a lot more charge/discharge cycles. Nissan won't publish exactly how much of the battery's capacity the Leaf is using, but they also give recommendations like not to charge past 80% if not needed. That would indicate they're using a much larger fraction of the battery's total capacity, if not 100%.


RE: same
By lelias2k on 6/7/2012 4:23:18 PM , Rating: 2
Actually, it uses a little more than 60% of its capacity.

And according to this C&D article the capacity actually increased 0.5kWh.

http://blog.caranddriver.com/2013-chevy-volt-gets-...

Solandri is spot-on about the reason to avoid fully charging/discharging the battery though.


RE: same
By Samus on 6/7/12, Rating: 0
RE: same
By Jedi2155 on 6/7/2012 10:48:13 PM , Rating: 2
"Deep cycling" a lithium battery is completely unnecessary. Although there is still the forming charge in the first 2 cycles, after that, the cells are relatively consistent.

A deep cycle is only necessary for the battery electronics to recalibrate its upper and lower boundaries, but the battery chemically does not require any type of deep cycling unlike lead acid/nickel based batteries.

Regarding the Volt battery pack, the battery pack performance was also improved in low temperature up to -20 C. Previously, the engine would be required to turn on if the pack temperature was < 0 C. Lithium batteries store less energy at lower temperatures. They can store more energy at higher temperatures but degrade faster. With the new battery optimization, they can store more at low temperatures, last longer at high temperatures, store more energy, and last longer overall (less degradation).

So yes, 3% is a little bit of extra energy, but that combined with improved controls/efficiency, netted an 8% increase in range. For some people, that is a matter of using gas everyday, to using gas once a week. I think that's a bigger difference there.

Regarding usable capacity, that is a function of temperature. The 2011-12 Volts uses 65% of capacity of the pack (more in Mountain Mode) which is nominally 10.4 kWh. Depending on temperature though this is actually 9.4 kWH to 10.8 kWh per charge.


RE: same
By Richard875yh5 on 6/8/2012 12:57:51 PM , Rating: 2
The Volt battery is purposely not discharged all the way because doing so would shorten the life of the battery. It's completely opposite of what your saying.


RE: same
By SlyNine on 6/9/2012 3:33:44 PM , Rating: 2
You should NEVER discharge a Lipo batter 100%. In fact whatever the voltage limit is you should never go below that. Balance charging can bring all the cells back over time, but still some damage is done.

The memory effect is a myth based on (NiMH)nickel metal hydride and (NiCa) nickel–cadmium batters.


RE: same
By SlyNine on 6/9/2012 3:39:31 PM , Rating: 2
I'm not trying to say the memory effect is totally a myth either, but much of what people think is happening is NOT because of the memory effect.


RE: same
By Jedi2155 on 6/10/2012 5:31:23 PM , Rating: 2
Discharging a battery 100% is not bad for the battery. Its discharging it < 2.0 volts per cell that causes issues. As long as it is above the voltage cut off it doesn't "hurt" the battery. You only increase risk of over discharging it, which is why YOU SHOULD NEVER discharge it more than 100%. Of course 0-100% is arbitrary value. 0% should always be a value with a margin of safety threshold of the minimum voltage cutoff so, as long as the designers did their job right, it should be "safe" to hit "0%".

Now keeping a battery at 100% charge, that is more degrading to the battery.


RE: same
By Dr of crap on 6/7/12, Rating: -1
RE: same
By mindless1 on 6/7/2012 8:01:59 PM , Rating: 4
What is it you don't understand? 3 miles more is about 9% improvement, nothing to sneeze at. Suppose every 3 years they managed to keep improving battery performance by 9%, that's exactly what we need to make EVs viable for the masses within the next two decades (besides the power grid improvements).


RE: same
By Jedi2155 on 6/7/2012 10:06:38 PM , Rating: 2
I think they actually change the chemistry and optimized the amount of active material within the cathode/anode to match GM's new specifications.

Its almost the exact same battery chemical, but just sizes are different. It would akin to shifting your PSU from your ATX case from the top of the chassis, to the bottom of the chassis, and as a result, got better airflow. At the same time, you realized you could clean up some bad wiring that was blocking airflow, in the new position.


RE: same
By Richard875yh5 on 6/8/2012 12:50:57 PM , Rating: 2
You are just guessing and I bet you are wrong. Unless you have proof of what you are saying, I would not make such an accusation.


GM Engineers?
By steven975 on 6/7/2012 12:36:38 PM , Rating: 2
So, was it GM Engineers that altered the chemistry or was it the Korean supplier?

I think that GM just said they wanted 16.5KWH and the Koreans said they could do it for the same price.

They're starting to sound like one of the big tech companies that say their engineers design every single thing.




RE: GM Engineers?
By mellomonk on 6/7/2012 5:18:55 PM , Rating: 2
It was GM engineers. LG Chem is the OEM manufacture building to GM specs & designs. The cells and overall pack was designed in the US. LG Chem is responsible for the industrial engineering to manufacture the cells. LG Chem is currently finishing up a plant in Holland MI to manufacture the Volt and future GM EV batteries.


RE: GM Engineers?
By mindless1 on 6/7/2012 8:04:48 PM , Rating: 2
There's a difference between providing specs for battery cell size, pack configuration, connectors and protection circuit, and actually providing the technical details to build it. Odds are low it was GM engineers that had anything to do with the chemical changes to the cells.


RE: GM Engineers?
By Jedi2155 on 6/7/2012 10:02:32 PM , Rating: 2
I believe LG Chem (in Korea) came up with the chemistry in the first place. GM said, we want more energy, better pack performance etc. LG Chem said, we can do it, and spends time optimizing the chemistry to match what GM specified. So the hard science and work was done by LG Chem, GM merely specified hey, we want a better battery.


RE: GM Engineers?
By mellomonk on 6/8/2012 5:42:39 AM , Rating: 2
LG Chem is one of the largest suppliers of Lithium ion cells in the world. Their automotive operations are based in Michigan where a fleet of American engineers design large scale automotive systems that are sold around the world. http://www.lgcpi.com/

The chemistry of the cells is but one part of a hugely complex battery design. The pack is 288 liquid cooled and computer controlled cells. Besides cooling and control, the design also takes into account vibration, impact, and possible fire. In short there were more then a few engineering hours put into it.

You can discount GMs engineering in such matters all you want. They have been involved in battery and fuel cell research and development since the 60s and have more then a few patents to prove it. They didn't just conjure the EV1 from thin air in the 90s. They have dedicated battery research in Brownstown MI as well as the Warren Tech center. Fuel Cell research is in Honeoye Falls, NY. These tech centers feed several GM subsidiaries including Electro Motive Diesel who builds many of the diesel electric locomotives you see riding the rails.

Old GM's failure as a car company had far more to due with marketing, design, leadership, and bean counters, then engineering. The tech is there when the powers in charge decide to invest in it's production. The very existence of the Volt shows that occasionally they are willing to take a chance. Now it remains to be seen if they are willing to take the slings & arrows, as well as losses it will take to mature the tech. Toyota sustained many years of losses to bring the Prius and it's tech to where it is today. GMs generally conservative approach to EVs and hybrids may be warranted given the slow uptake from the general public. None the less it is nice to see the Volt make it to production.


RE: GM Engineers?
By Jedi2155 on 6/8/2012 10:00:59 PM , Rating: 2
I never discounted the ingenuity and capability of American engineers, but this is the pure battery I'm talking about. I'm not sure if LG CPI (Formerly just CPI) developed the chemistry to begin with, but GM did not develop it. They did do a lot of the hard work in developing the battery system, which I consider to be far more advanced than the battery itself, and far more impressive.

A battery by itself is pretty boring....but when you can integrate it in a system, and do it well....that's real engineering. I'm sure that is all done by GM of course. I wouldn't trust LG to do it...


How about kWh/100m instead of MPGe
By ATX22 on 6/7/2012 1:43:35 PM , Rating: 1
This would probably be better for electric vehicles instead of hybrids, but honestly... if it's so important to be driving around in electric cars, how about focusing on how efficient the motor and drivetrain are instead of trying to convert it over to some liquid fuel derived metric. Maybe even rate the efficiency of the ICE and electric drivetrain separately in hybrids.

Even the less intelligent people out there could figure out that car A has a higher or lower kWh/100m rating that car B without having the EPA start converting it into stupid-high "equivalent" number.




RE: How about kWh/100m instead of MPGe
By Solandri on 6/7/2012 3:03:27 PM , Rating: 3
Flawed as the MPGe rating is, it's supposed to comparable to regular MPG on an energy basis. That is, if you have 1 kWh of electricity in an EV and 1 kWh (3.6 megajoules) of energy worth of gasoline in a regular car, the difference in their ranges will be the ratio of MPGe to MPG. About 2/3rds of the energy in gasoline is converted directly into waste heat without doing any mechanical work. That's why the MPGe ratings are about 3x higher than for similar-sized gasoline vehicles.

This isn't really a fair comparison though because the equivalent efficiency loss for electricity happens at the power generation plant. Whereas an ICE throws away about 70% of the energy in the gasoline as waste heat, a coal plant throws away about 60% of the energy in coal as waste heat while generating electricity.

As it happens though, at $3-$4/gal fuel prices, the MPGe/MPG ratio is pretty close to the ratio in cost per mile. i.e. if you put about $3.50 worth of electricity into an EV (at the national average of $0.12/kWh) and $3.50 of gasoline (1 gallon) into an ICE vehicle, their ranges will be about the same as their MPGe vs MPG. So if gas is around $3-$4/gal, you can think of MPGe as how far you could travel in the EV if you took the money for 1 gallon of gas, and spent it on electricity instead. If gas prices are higher, then the EV does even better. If gas go lower, then the EV doesn't do as well.


RE: How about kWh/100m instead of MPGe
By Jedi2155 on 6/7/2012 10:53:52 PM , Rating: 2
In addition, they do report the kWH/100 mile figure here and there. Such as the MyVolt.com website. The calculation is fairly simple though given the EPA information.

2011/12 Volt (100 miles * 35 MPC) * (16 kWH * 0.65) = 29.4 kWh/miles.

2013 Volt (100 miles * 38 MPC) * (16.5 kWH * 0.65) = 28.2 kWh/miles.


By Jedi2155 on 6/7/2012 10:55:39 PM , Rating: 2
kWh/ 100 Miles*


RE: How about kWh/100m instead of MPGe
By Mint on 6/10/2012 4:04:51 PM , Rating: 2
The 16, 16.5, and 0.65 figures need manufacturer info and are subject to change and bias.

Just do 33.7/MPGe to get kWh/mile. For the 2013 Volt, it'll be 33.7/98 = 0.34 kWh/mile.


So...
By Sazabi19 on 6/7/2012 12:36:44 PM , Rating: 4
Now my battery tastes better? I think that's what I was supposed to take away from this.




RE: So...
By geddarkstorm on 6/7/2012 12:59:24 PM , Rating: 1
Nothing has that smooth, delicious taste like lithium poisoning.


RE: So...
By stardude692001 on 6/7/2012 2:08:09 PM , Rating: 2
why are all the good things poisonous? I miss asbestos and mercury.


RE: So...
By johnsmith9875 on 6/13/2012 5:24:41 PM , Rating: 2
All enjoyable technology is dangerous, like super strong magnets. I wonder how many fingertips those little marvels have crushed over the years.


FIYA
By Ish718 on 6/9/2012 11:32:48 PM , Rating: 1
Will it catch on fire? I guess there is only one way to find out...




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