New lithium ion process could lead to fast charging, still needs BIG pipe!
Researchers at the Massachusetts Institute of Technology have been looking at where the bottlenecks are inside lithium ion batteries that limit charging and discharging rates learned some interesting things. Lithium iron phosphate chemistry is particularly promising in terms of high charge and discharge rates. They found that some new processes for manufacturing the lithium phosphate coating on lithium iron phosphate crystals could provide for better access to the lithium ions allowing them to move around more readily. This all sounds similar to the premise behind the lithium iron phosphate batteries produced by A123 Systems and the lithium titanate cells produced by Altairnano. The increased surface area of material allows more ions and electrons to move in and out without heating up as much as lithium cobalt oxide cells. The result is that cells made with these materials can be charged at very high rates without degrading the charge capacity over time.
The downside is that at higher charge rates, the maximum energy density of the cell decreased although the power density is improved. The bigger issue remains the power needed to actually charge an automotive sized battery pack in a few minutes. A five minute charge would require 180 kW or more, not something available at home or any existing charging stations.
[Source: ars technica]
Reader Comments (Page 1 of 2)
PeterG 9:56AM (3/12/2009)
I think it is clear than within 10 years, batteries won't be the bottleneck in charging times.
The limit will be more about how much current can be supplied.
This still will not make electrics the ideal cross country cruisers, but it will let them cover 98% (stat pulled from the ether) of usage with ease.
Reply
Stan Wellaway 10:30AM (3/12/2009)
Time taken to recharge, and limitations on distance per charge, are two of the main arguments thrown at EVs.
With so much attention and money now being poured into battery development all over the world, it does sound as though there is a serious possibility of overcoming the first of those two hurdles. In which case that second hurdle becomes less of an issue anyway. But with Tesla already claiming 200-250 miles per charge for its sports car, and Smith Electric Vehicles claiming 100-150 miles for its all-electric trucks - that second hurdle too is starting to crumble.
Reply
pgrt 10:38AM (3/12/2009)
a super capasitor or a proxy battery to your home/charging station? then you have the energy at your home and the bottle neck is just how fast the proxy battery can give out its energy. Sure it generates heat but it can be used to warm your house in winter and i think people wouldnt mind about that if they can load their cars faster. The problem is just the cost of buying one more big battery pack to your home.
Reply
cw 11:14AM (3/12/2009)
Agree that a bank of ultracapacitors would fulfill this function nicely. The ultracaps "charge" while you're driving the car, then dump their charge into the car with little resistance when you get home. Kind of like a 32kWh camera flash.
Curt Barger 11:02AM (3/12/2009)
"The downside is that at higher charge rates, the maximum energy density of the cell decreased although the power density is improved."
For those of us who don't understand the difference between "energy density" and "power density," can someone provide an good lay-person's explanation? Thanks
Reply
cw 11:08AM (3/12/2009)
Power is simply the amount of energy used, per unit time. The total amount of energy in the cell is lower, but the amount of power it can deliver at any moment, for its weight, is higher.
Hope that helps.
Curt Barger 11:47AM (3/12/2009)
Thanks, cw
it does help
Sam Abuelsamid 1:55PM (3/12/2009)
Energy capacity is the equivalent of the size of your gas tank. The more energy you can store, the farther you go. Energy density is the amount of electrical energy that can be stored in a given volume/mass of battery. Lower energy density means less range for a given size of battery.
Power is the rate at which the battery can charge or discharge or the amount of time it takes to get each kWh or juice in and out. This affects vehicle performance and tells how fast you can use up the available energy.
Energy and power tend to be somewhat orthogonal in batteries, more power comes at the expense of energy and vice-versa. Hybrid batteries are biased toward power, EV batteries toward energy.
Chris M 3:27PM (3/12/2009)
"Power" is the rate of flow of energy at any instant in time, and "energy" is the total flow of power added up over a certain period of time. Power is measured in watts or Kilowatts (1,000 watts) and energy is measured in watthours or kilowatt-hours. It is similar to the difference between distance (miles or kilometers) and speed (miles per hour or Kilometers per hour).
Sam has a good analogy, the total energy in the battery gives a rough estimate of how far you can go, just like the size of the gas tank determines how far a gas car can go.
Power of the battery determines how fast that energy flows out, thus how powerful a motor it can run and how fast the car can move. The analogy would be how big the fuel line is from the gas tank.
Tim 12:35PM (3/12/2009)
Rapid charging does NOT require grid upgrades!
Each charging station could have a bank of these batteries which accumulate and store power from the grid. An automatic control system could monitor which packs are charged and make them available to shunt their power to the packs on the cars on demand just like a gas pump.
As EV numbers increase, more battery banks could be added for more charging locations at each station. These banks could be mass produced in a factory and placed on skids or in shipping containers and stacked/added as needed.
Modularity = efficiency = lower cost!
The grid is NO excuse! Electricity is NOT hydrogen and we have an infrastructure!
According to DOT’s research, 78% of ALL trips are less than 40 miles, 85% are less than 50 miles, 90% are less than 60miles, and 93% are less than 70 miles!
http://www.gm-volt.com/2007/12/06/how-did-gm-determine-that-78-of-commuters-drive-less-than-40-miles-per-day/
E-REVs like the Volt won't need rapid charging. Most people will recharge each night at home because it will be FAR less expensive than daytime rapid charge at a station.
The higher cost will mean that daytime rapid charge will only be used for those occasional long trips and those who forget to plug in at home. I doubt they will forget to plug-in a second time.
We can upgrade the grid slowly over time, but not all at once and not before EVs are widely available. Load-Leveling will help the grid, lower the cost of electricity and the efficiency will help the utilities afford the upgrades.
Advancements are being made every day regarding increasing the efficiency in producing, transmitting and storing electricity.
Again, upgrade over time, with rapidly advancing technologies paid for with efficiency savings instead of taxpayer debt. (paying interest sucks!)
Act in haste then repent in leisure. Measure twice, cut ONCE!
Reply
Chris M 4:16PM (3/12/2009)
You have a point. Plug-in hybrids don't need fast charging, even though they will be the ones using the high power batteries suitable for fast charging.
But I'm not so sure a fast charging station with banks of batteries is such a good idea. Pure EVs are more likely to use high energy density batteries that are not well suited for fast charging, and if you're going to have a big bank of reserve batteries at the station, then wouldn't it be more efficient and make more sense to simply swap batteries like PBP is planning? That would reduce the energy loss caused by running the energy through two sets of batteries (about 15% loss).
Of course, if someone were to come up with a high energy/high power battery, that might change the equation.
Tim 4:51PM (3/12/2009)
Chris M said:
"if you're going to have a big bank of reserve batteries at the station, then wouldn't it be more efficient and make more sense to simply swap batteries like PBP is planning?"
No, because standardization this early in the game would limit innovation and design flexibility. Why do I want to pay a monthly fee for my battery pack... FOREVER?
Personally, I like to own instead of rent and I believe that the majority of people would agree. The PBP model locks you into a payment for the rest of your life. Not everybody likes that idea. Fast charging makes the PBP model irrelevant.
oollyoumn 11:24AM (3/12/2009)
But does anyone really need a 5 minute charge at home? I don't see any reason a slower charge will not work with home level capacity. This should allow very fast recharges at designated charging stations that would have the capacity. Maybe a drive through with no stopping. 10 - 20 seconds and just keep on moving, like a very fast car wash.
Reply
sp 11:35AM (3/12/2009)
Current batteries can already charge in 5 min. And current batteries already have the energy power tradeoff where if you discharge them faster total energy will be less.
Current infrastructure cannot charge a battery in 5 min let alone 20 seconds. These batteries may displace ultra caps though.
Reply
meme 1:00PM (3/12/2009)
"A five minute charge would require 180 kW or more, not something available at home or any existing charging stations."
Aerovironment makes chargers as big as 250kW or so; that's what AltairNano packs are tested with.
Reply
jake 1:57PM (3/12/2009)
Isn't the 250kW charger just a one-off demonstration charger?
I think their typical rapid chargers for single vehicles are 30kW, which would take about an hour to charge for 100-150 miles of range.
The more widely used airport chargers for baggage loaders are 80-60kW and that'll take about 20-30 minutes to charge a car for 100-150 miles of range. I think that is good enough for most stations. I believe the demonstration general EV charging stations in Hawaii use 60kW chargers.
A 180kW charger will cut that time to 10 minutes, but so far I don't think it's commercially used. I think in real life, the stations will have to weight the costs of each type of charger (efficiency might also affect the price of electricity they charge for that charger) and whether they have enough power to use the high power chargers.
meme 2:18PM (3/12/2009)
Isn't the 250kW charger just a one-off demonstration charger?
It's in their catalog, although I believe it's marketed as for pack testing purposes at this point.
I think their typical rapid chargers for single vehicles are 30kW
They have 60kW chargers installed across Oahu.
NorthernPiker 2:58PM (3/12/2009)
In an EV, the application of this power battery would be for performance - improved acceleration and greater recapture of energy during braking - up to the limit of the EV's electric motors. An energy storage capability of 1/4 to 1/2 kWh will be enough since the kinetic energy of a 4,4000 lb. car at 60 mph is 200 Wh.
These power batteries, like ultracaps, would be used to shoulder most of the burden of hard acceleration and braking, i.e., extreme discharging and charging, respectively, while the energy batteries would provide the EV's range - 5 miles per kWh for a Prius-sized vehicle.
This arrangement provides two benefits. Firstly, the energy batteries will last longer without high power surges. Secondly, the performance (primarily from the power batteries) of a PHEV would not be notably dependent on the energy batteries; so, the all-electric range of the PHEV can be tailored to a user's normal daily mileage which would avoid the cost of under-utilized, extra energy batteries.
Reply
Chris M 4:31PM (3/12/2009)
Very good point. The Altairnano battery has very high power density and very high life cycle count, but lower energy density than other LiIon batteries. Those characteristics would make them good choices for small hybrids and an excellent choice for a "power buffer" for a high energy/lower power EV battery.
If the Altairnano power density is sufficient, it could prove to be better and cheaper than ultracaps for power buffering, with a higher energy density to boot.
But the Altairnano battery currently is too expensive and has too low of an energy density to be the main battery for EVs.
David Herron 9:53PM (3/15/2009)
Fast recharge will always require a big pipe. The power required to move a vehicle of a given weight is determined by laws of physics, and that power turns into a number of kilowatt-hours of electricity, and that turns into huge kilowatts of juice required for a quick recharge.
Reply