WSJ: GM moving to Lithium Ion; Li-ion could give Prius 80 mpg

"Analysts believe a Toyota Prius with lithium ion batteries could go about 80 miles on a gallon of gas, up from about 50 now...."

I'll believe it when I see it. I seriously doubt that changing the battery from Nickel Metal Hydride to Lithium Ion will radically improve overall automobile mileage efficiency . Although Lithium Ion batteries have a much greater storage capacity per unit volume, the efficiency ( energy out / energy in ) isn't radically improved. Anybody out there have any actual data comparing battery types???

Keith

 

No data here --

But, if the Lithium Battery goes into production, I'm wondering whether it could replace the Nickel Hydride batteries in place, in Prii that are already in use ?

Or, whould it require extensive or prohibitive re-wiring ...?...

 

Not likely. The battery characteristics and management system built into the Prius means it will only work with the NiMH pack. Retrofitting existing cars to use a new battery chemistry will likely prove to be too expensive. The only option for LI-Ion in older cars will be for an "add-on", booster pack that isn't charged by the vehicle ... only by plugging in.

Li-Ion packs will make the OEM PHEVs come alive.

 

I don't know about 80 mpg from 50 mpg, but I am certain of improvement in some form even for non-plugin setup. Maybe that is the next Prius that is rumored to have mid-65 mpg without plugin (even with a larger 1.8L ICE).

Why not setup to have Lithium battery to have equal storage/voltage capacity as the NiMH? Since Lithum has more than 90% energy transfer/storage rate compare to NiMH (mid-30%?).... there is your improvement there... plus another 120 lb or so weight saving.

 

Doesn't Lithium-Ion have a shorter life? I.E. the batteries won't last ten years. And aren't they limited to a certain number of recharges?

I can see Lithium Ion as an additional pack, but not as a replacement for the NiMH.

I think a new battery technology is still coming that give the benefits of both together. I also think it's going to be coming pretty soon given the demand.

 

The "battery characteristics and management system built into the Prius" does NOT mean it will only work with a NiMH pack.

I wouldn't put it past Toyota to design the new Lithium pack to be compatible with existing Prii form factor. If so, all it would require is a software update for existing Prii to take advantage of a Lithium pack, to the maximum physical extent of the existing Prii's capabilities.

 

"analysts" pfft! Some clueless MBA's who make their living guessing. Reminds me of the tabloid articles that always quote "Swiss scientists" about two headed aliens. Nice work if you can get it, but does anybody take them seriously. Oh, wait. isn't Chelsea an analyst?

 

Me too. Where do people think this additional 30MPG is going to come from? Simply changing the traction battery pack from NiMH to Lithium ion merely changes the electrical storage medium - it has no inherent energy content, as does gasoline. While Lithium ion batteries exhibit electrical storage capacity up to twice that of NiMH, thus enabling longer EV range ability, that energy has to originate somewhere. Having to replace the additional electrical energy in the battery pack will consume more gas, so the MPG may even decrease, since these energy exchanges involve inherent inefficiencies. The questions of cost, temperature stability and weight have also to be considered for a viable system to evolve.

Only by providing plug-in capability to the next generation Prius does the Lithium ion battery make sense, either by re-charging from solar arrays by day, or from the grid overnight during periods of minimum power station draw.

rah

 

The only way a Li-ion battery (or any other battery) would improve performance is:

1. Lower internal resistance so can handle higher charge/discharge rates. Being able to accept higher charge rates means that you can use regenerative braking more instead of having to augment braking as much using the friction brakes. Higher discharge rates (along with a motor that can handle those rates) mean faster acceleration on battery power alone is possible.

2. Lower internal resistance so less energy is lost when charging or discharging (charging/discharging becomes more efficient).

3. Better weight/energy storage ratio. You could use the same capacity battery and reduce weight of the vehicle which improves efficiency, or increase capacity to give you more room to charge the battery now that you can capture more energy while braking.

I highly doubt that economy would increase from 50 to 80 mpg because of a battery upgrade, unless that battery upgrade also let you plug it in to charge it.

 

The article is misleading.

The new Prius will have better mpg possibly up to 70mpg but its not just the battery pack that will do it. The engine will be a little more efficient, the charge controller will help greatly as well.

There is up to 5% more efficiency that can be wrung out of the voltage step up and down electronics and the motor controller.

The power split device <transmission> is a great design but shows its flaws at speeds over 50mph as mg1 and mg2 have to work hard at higher speeds. A design change here ALONE could make highway mpg go up 10%.

Finally a more radical idea that could be in the next Prius is a turbogenerator. This device would use the exhaust to drive a turbine and extract energy for the battery system. This system would create far more power then the backpressure it causes.

The Prius is the most efficient production vehicle on the market but there are still many advances that could improve it.

 

Ron, I believe part of the extra charge energy will come from the times when you are driving on the freeway or rolling down hills and you have reached your max charge on the smaller NiMH and cannot hold any more energy yet the larger capacity Li-ion battery could hold more. Full charge happens quite often during my daily commute.

I am not sure about the claims of 80mpg but I could see this as potentially better milage than the current stock battery system even if plugging in wasn't an option.

 

I would SERIOUSLY doubt that Toyota would market and sell any sort of supported upgrade package for existing Priuses. They're in the business of selling cars not an upgrade that will likely be very expensive. The market would be too small and the small quantities again lead to a high cost.

It doesn't make sense for them to invest the effort to go through the design and validation process (have you ever seen some of the effort that goes into testing cars?) for a 4.5 year old design. I'd imagine that they hit the drawing board starting in 2000 or so, if not earlier.

They really need to have a business case and it'd make more sense to put new technology in a next gen car.

 

LOWER INTERNAL RESISTANCE - That's why I was entrigued by this development...fascinating if true... http://priuschat.com/forums/prius-m...mate-prius-battery-mod-44-better-mileage.html