It’s commonly asserted by many people and a few companies that the future of transportation is electric cars. One thing electric cars need a lot of is battery capacity - it’s what makes them electric, and sufficient battery capacity is what makes them a genuine replacement for a car powered by an internal combustion engine.
(Comments from Blogger)
2015-12-06 by Robert Moser
Interesting read. It’s always fun to take one of these napkin-math journeys. I’m surprised that Lithium Iron Phosphate isn’t being used more often- it has a lot of advantages for, what, ~15-20% greater volume? That seems to me to be close enough to be strongly considered. Is it a patent/legal issue? I know A123 had a bunch of the patents for using lithium iron cells in batteries, and who knows what happened to those after their bankruptcy…
2015-12-06 by Russell Graves
I don’t think it’s a patent issue - there are plenty of LiFePO4 cells on the market. I think the lower energy density is enough of a deterrent for most uses that nobody seriously considers it. The cycle life of NCA and NMC has improved so there’s no longer a clear advantage in the LFP packs on that front.
I’m certainly a fan of it, as it’s safe, and doesn’t use anything particularly exotic, but other than the occasional electric delivery vehicle, it doesn’t seem like many people are doing much with it. I’d love to know why.
2015-12-06 by Robert Moser
I went poking around the 'tubes for more info, and came across this:
http://qz.com/338767/the-man-who-brought-us-the-lithium-ion-battery-at-57-has-an-idea-for-a-new-one-at-92/
Control+F ‘Phosphate’ to get to that particular part; it looks like patent fights may actually be a large part of it, at least when it comes to traction-sized battery packs.
The whole article is an interesting read.
2015-12-06 by Unknown
Perhaps the solution is to go to a “partial pack” system. You make two types of power packs. One is “full strength” and good for 200+ miles. The other is the same size and shape, but is lighter because it only carries a quarter of the actual cells. This gives a 50-mile range, which should be more than enough for a daily commute. This won’t reduce the total cobalt required by 75%, but it should cut it in half.
If electric car manufacturers go with battery pack swaps for rapid recharge, you could simply indicate what kind of pack you want and the appropriate one is loaded for you.
2015-12-06 by Russell Graves
If I’m not mistaken, Tesla built pack swap capability into the Model S. They then decided that it wasn’t worth supporting long term and they should focus on faster charging.
I don’t see regular pack swaps as a viable solution, and I’m fairly certain Tesla doesn’t either, at this point.
You might be able to do something series hybrid like with an 80 mile pack and then an air chemistry primary cell, but again, that will require pack swaps, which sounds like the gas station trips so many EV owners have learned to hate.
2015-12-07 by Seriously in need of hair for a haircut
I’d be curious how much of the 50 gram weight of the cell is battery casing/contacts/etc, or rather, non cathode/anode weight? Could throw off the calculation a bit.
2015-12-07 by Russell Graves
The numbers I was working for cathode mass fraction specifically split out casing weight as a separate line item, so that’s already accounted for in the numbers. For 18650s, around 25% of the weight is housing. Since I was working with the data for individual cell capacity instead of full pack capacity, the assembly of the pack doesn’t factor in at all. I believe about half of the Model S battery pack weight is battery cells, and half is support systems/structure/etc.
2015-12-07 by Unknown
Tesla used the pack swapping to get the “fast refuel” CARB credits.
They seemed to always think that pack swapping wasn’t a good mas scale solution for obvious reasons (Just think of how many 240kW quick chargers you can install for the cost of a single pack swap station).
Thanks!
2015-12-07 by Unknown
The other option is to follow Nissan and go for LiMn cells.
They are very cheap and don’t contain any (known) exotic elements.
There are many chemistries available all with many tradeoffs, including material availability.
Lithium, Cobalt, and Manganese are all super cheap today.
http://batteryuniversity.com/learn/article/types_of_lithium_ion