[eagle]

I thought that LiFePO4 were safer and technically superior to lithium-ion batteries, so why is it that I still see NiCad, Lion, etc inside of a Prius, Volt, and Leaf?

 

[tomofreno]

"Lithium-ion" and "Lion" are just generic terms for all battery chemistries where the mobile ion moving between anode and cathode is lithium. There are at least 18 different battery chemistries of this type, only a small number of which are in production. I think the Leaf uses LiFePO4 and the Volt uses a different chemistry with Mg which has a bit higher energy density but which is also more temperature sensitive, hence the requirement for better temperature control of the battery pack on the Volt. Toyota has been the laggard on ev development, despite being the first to market with a hybrid. They have stuck with nickel metal hydrid batteries on the hybrid, but I think the PHEV models will use a lithium based chemistry. It seems to me that NiCad is used mostly on trucks where weight isn't quite as much a concern (but is being displaced by lithium), and older ev's. The infamous laptop pc batteries which can catch fire under certain circumstances are a lithium cobalt chemistry. There are also lithium polymer cells made for example by Kokam, which have higher specific energy than the other lithium cells, but shorter cycle life and much higher cost. Most on this forum use the LiFePO4 chemistry since they are available at relatively low cost from China as so-called large format or prismatic cells. A U.S. company, A123, makes smaller cells with this chemistry, but they are higher power than the prismatic cells due to different fabrication technology, and more expensive. So you can see that referring to all lithium chemistry cells by some generic term as if they were all the same is misleading.

 

[eagle]

Wow. That was a great explanation--thanks.

 

[Sunking]

The real issue is cost.

 

[Duxuk]

Spoke to a mate of mine, Dave, who is in the design department at Leyland Trucks in the UK. They have a Lithium powered truck of about 12 tons which can do 100 miles on a charge.The pack cost £80,000! He doesn't think that a truck could EVER be an economic proposition with Lithium. Sorry, I didn't ask in any more detail about the battery chemistry. We were having a good few beers and a curry at the time-It didn't seem relevant!!!!!

Andrew. (Carbon fibre lead acid trike, 30 mile range in theory but that will wreck the batteries. £600 for the 72V pack)

 

[JRP3]

I think both the Volt and LEAF use LiMn chemistry of some form.

 

[tomofreno]

I think both the Volt and LEAF use LiMn chemistry of some form.

Do you have a reference JRP3? Would be nice to know what they use for certain, so I can stop prefacing with "I think."

 

[JRP3]

Other than article references I can't find anything official. I'm googling.

 

[JRP3]

Seems credible:

Nissan’s new batteries consist instead of sheets of lithium manganese and graphite, stacked in waferlike cells, each about the size of a manila envelope. Four of these cells get packed into a box the size of a textbook. Nissan managed to fit 48 such boxes beneath the seat and under the floor. Simple airflow is enough to cool them. The battery can deliver 90 kW of power and has an energy capacity of 24 kWh, about twice that of Nissan’s previous lithium-ion batteries of the same size. And Nissan’s already working on a version with a lithium nickel manganese cobalt oxide cathode, which might double again the battery’s capacity.

http://spectrum.ieee.org/green-tech/advanced-cars/nissans-allelectric-leaf-doesnt-stint-on-performance

 

[DJBecker]

I'll start out with the baseline: none of the batteries make economic sense. Even if you believe that oil prices will be dramatically higher in the near future, you would be better off over-paying for an oil hedge.

That said, the real issue is battery longevity, both age and cycle life. There is no battery cheap enough to pay for itself with a 100-300 cycle recharge life. Nor is a 3 year room-temperature half life acceptable, especially if the range starts at 40 miles when new and is under 20 miles when it's still pretty much new.

That's the main reason that LiFePO4 batteries are appealing -- the promise of 3000 cycles at 70% DoD and a 10 year service life. Of course no one has demonstrated that yet, but at least there is the chance it could happen if the cells are treated perfectly. Most of the other battery structures have been proven to not come close to that longevity.

 

[JRP3]

That's not entirely true, Wayland has tested Kokam's LiPo to 2K cycles I think, Altairnano's Li Titinate even higher, though they are more expensive.

 

[MN Driver]

Do you have a reference JRP3? Would be nice to know what they use for certain, so I can stop prefacing with "I think."

Search Youtube for 'Chevy Volt Battery Deep Dive' and they talk about LG Chem and their Lithium Manganese cells. They show pictures of the cell balancers installed and the pack itself outside of the car, it's capacity, how the capacity is used, stuff like that. Ford and Hyundai have both discussed their LG Chem battery packs as well, different configuration but seem to be using the same thermal coolant jacket sandwiched between every 2 cells(so one side of every cell is in contact with heat exchange) that I presume was designed by LG Chem.

LG Chem is going by the Compact Power, Inc name for its US operations.

Nissan Leaf has batteries manufactured by Automotive Energy Supply Corporation, they are also LiMn.

I used to see spec sheets of LiMn show 500-1000 cycles before but apparently the chemistry has improved since the auto manufacturers are putting long term warranties on them and GM went through quite a bit of testing as well before deciding to go with LG Chem.

 

[JRP3]

Of course GM is shallow cycling their pack so even a 1000 cycle cell will probably last far longer.

 

[tomofreno]

That's not entirely true, Wayland has tested Kokam's LiPo to 2K cycles I think, Altairnano's Li Titinate even higher, though they are more expensive.

I attended a presentation by the then head of technology at Altairnano in early 2008. He claimed that the principle advantage of lithium titanate was the lithium ions could move through it without strain. He claimed they had demonstrated over 20,000 cycles, operation over much larger temperature range, and much higher power, though lower energy storage than most other lithium chemistries, and handed out brochures stating the same. They seem to be a strange company though. Never seem to go anywhere, and are very top heavy. He never returned my calls about using their cells in my car. The higher power is only really required by drag racers and the lower energy density is a real drawback. The much wider temperature range and much longer cycle life is appealing though.

 

[MN Driver]

Of course GM is shallow cycling their pack so even a 1000 cycle cell will probably last far longer.

All of the production EVs will be short cycled, the question is, to what extent.

With a full EV, usually people aren't driving to the final few miles every day so a slight undercharge would likely do well and then some leftover Ah would be good for the bottom end to keep warranty claims down for those who take heavy swings through their pack capacity constantly.

 

[tomofreno]

So if Nissan and GM are using the same cells, why is GM shallow cycling and Nissan not? And why has Musk attacked Nissan for using the cells and not GM? Because GM is shallow cycling and doing better thermal control? Ford is apparently using lithium polymer from LG Chem (U.S. subsidiary Compact Power). So are the GM and Nissan cells the same?

 

[MN Driver]

No, Nissan is using cells from a completely different company. They are 'air cooling and heating' them by putting them in a box underneath the passenger compartment/floor. I'm very curious to see what performance impact the Leaf has when driving it in the -20 degrees F temperatures that we get once a year and the multiple times we get -10.

From what I've seen about what Musk said, it seems it was because of the simple nature of their pack being less sophisticated than even Tesla's first prototype. I think Musk said something about the Leaf because the Volt really isn't in competition to the Leaf. ...IMHO I don't find the Leaf in competition to the Tesla, someone who wants a Tesla isn't going to settle for the Leaf if they have the cash.

Using cabin air would be pointless, I wouldn't heat the car nearly as much as the next person and with my current car, I've driven it 15 miles in sub-zero temperatures without using heat. With electric heat, I'd be even less inclined to use it knowing there is less available range with it and I'd be sagging my voltage more, losing performance when accelerating with heat going.

LG Chem cells are going into GM, Hyundai/Kia, and Ford. They are not the same cells, each manufacturer is having them made to the size and energy/power configuration they want.

Hyundai is using them in the Sonata Hybrid and it has an EV highway pulse and glide mode and cycles the pack heavily, likely small cycles directly in the middle but it will run the engine a minute and have it off for a minute or so cruising down the highway. From some testing by Wayne Gerdes on CleanMPG, it seems to work well. Impact on battery life? I'm sure it was tested heavily before implementation. The Sonata cells are produced with more emphasis to power density than energy density.

GM cells are putting more emphasis to energy density than power density.

Ford is being quiet about the performance specs of their electric car but they just released a bunch of vague info with the cars pre-production release at CES earlier this month, but pretty much every car news site has something along the lines of '23kwh pack with 6.6kw charger, 3 hours to charge, same range as Leaf, who knows the HP'

 

[JRP3]

I attended a presentation by the then head of technology at Altairnano in early 2008. He claimed that the principle advantage of lithium titanate was the lithium ions could move through it without strain. He claimed they had demonstrated over 20,000 cycles, operation over much larger temperature range, and much higher power, though lower energy storage than most other lithium chemistries, and handed out brochures stating the same. They seem to be a strange company though. Never seem to go anywhere, and are very top heavy. He never returned my calls about using their cells in my car. The higher power is only really required by drag racers and the lower energy density is a real drawback. The much wider temperature range and much longer cycle life is appealing though.

Yes their poor density really makes them a poor fit for passenger EV use. They are being used by Proterra in some buses, and they are trying to target grid applications such as frequency regulation where their fast charge/discharge ability and long cycle life are a real benefit and the poor density is not a problem. I think they are on the verge of being taken over by a Chinese company at this point.

 

[JRP3]

All of the production EVs will be short cycled, the question is, to what extent.

The difference is that the Volt is locked in at only 50% pack capacity where the LEAF has the potential to use much more, though I agree that most daily use will shallow cycle the pack. Someone could use all of the LEAF's allowed capacity every day resulting in maybe 80-90% DOD, (don't know true pack size), a Volt owner can never do the same.

 

[JRP3]

Ford is apparently using lithium polymer from LG Chem (U.S. subsidiary Compact Power).

LiPo cells, are you sure? I didn't think any production vehicles were going that route yet.