Nickel Metal Hydride Battery

The 0th gen battery was different. It used cylindrical cells. So you can't compare even with the 1st gen.

 

I'm glad that Toyota kept the NiMH on the Prius v. When I buy a Toyota (or any car), I want reliability and at least the NiMH has a track record.

 

Taxi use is different. 50 fares a day means 50 entries/exits to the rear seat. That creates excessive lint which clogs the battery fan, and then the hybrid battery has no effective cooling. There is a TSB for this in Gen III. Plus, taxi drivers, while being the best drivers in the world, are also about the most aggressive drivers in the world. So you have a traction battery getting a heavy workout with severely impaired cooling. It almost doesn't matter whether the car is in Phoenix or Fairbanks.

As far as Lithium goes, we are at the stage that Toyota was at back in the late 90's, where they had D cell NIMH sticks for the NWH10, and large format NIMH for the RAV4 EV. Now, they have an experiment running with 5Ah cells in the Prius Alpha+ in Japan, and 21Ah cells in the PHV. Other vendors (Sanyo, LG, A123) are still at the experiment stage as well in terms of fleet size. That said, the next version of the C is an excellent candidate for a lithium due to the size/weight constraints.

 

Nissan is offering 8yr/100,000mi warranty for the Leaf battery and Chevy Volt the same for their battery. This is very impressive considering BEV or PHEV use is more more rigorous than HEV use because of the much higher depth-of-discharge. Effectively these manufacturers are offering the same warranty as the Prius c even though their batteries are much more highly stressed.

The Prius NiMH battery has a specific energy density of 41Wh/kg. Compare that to A123System's LiFePO4 prismatic cell (the one most likely to see auto use) 131W/Kg. That's more than 3X the energy density of the Prius c battery! Toyota could double the energy density of the present Prius c pack and still save considerable weight! Couple that with the wider temperature range of LiFePO4, the lower self discharge rate, the higher voltage/cell--there's just no arguing the superiority of LiFePO4 over NiMH.

It's hard to find direct cost comparisons, but LiFePO4 chemistry is roughly $650/kwh vs about $450/kwh for NiMH. So for the Prius C's puny 0.9kwh traction battery we talking only ~$200 more for LiFePO4. Would I spring for that? Hell yes!--and supersize me.

Maybe next year...

 

Portable Batteries Cycle Performance

The doe has the cost of li going down to $300/kwh by 2020, Japanese government $225/kwh. They may be optimistic, but cost is already down to $600/kwh for ford, and I would assume Toyota. This means lithium should be less expensive in the near future, but toyota can make it cheaper today. The prius c's battery would require only about 0.8 kwh of lithium mh to have the power.

Lithium cycles better than nimh, so it should have a longer life even using a larger state of charge.

Which is likely the major reason toyota is not on lithium yet for the prius c. More real world miles and tests. CARB has been the biggest road block to the spread of lithium battery technology, because they claim its part of the pollution control system of a hybrid.

+1

Anyone that thinks that nimh is better for applications should go out and buy a cell phone or lap top with nimh. There is a reason these and high end cameras have all moved on to lithium mh or lithium polymer.

 

I thought mostly to counter self-discharge and deep DOD in those consumer products -- neither of which are particularly (if at all) relevant to HVs.

Pick the best tool (and best value) for the job.

 

You don't think it is? I'd say it's pretty fundamental. A hybrid without a battery is a regular car.

Manufacturers can't complain. They fought ZEV and got AT-PZEV.

 

Yes, I know about those warranties, but how long have the cars been shipping vs. Priuses or Honda hybrids? How long have people been able to go on original NHW11 or NHW20 batteries vs. how long those cars have been shipping?

Tesla's been shipping their Roadster longer and yet they have much shorter battery warranties.

From (regarding the Prius Plus, 7 seater version of Prius v w/HV battery in center console/armrest area)

 

Nimh is a mature technology so are a hacksaw, hammer, and space shuttle does not mean they cannot be used.....
Lithuim is a developing technology
All technology have advantages , disadvantages, pros, cons, and risk..........

 

When a car is designed, they set goals. The goals of the Prius c were to be efficient, inexpensive, and reliable. Yup, LiIon might be a better battery, but for the application and the requirements, the Nimh was a better engineering decision. Every engineering decision has pros and cons but the LiIon likely didn't bring enough to the table to counteract the potential reliability issues and the cost. It wasn't Toyota trying to dick over the customers.

Strongbad - you're being dramatic and it really sounds like you want Toyota to go bankrupt building a car for you. Until you start buying thousands of cars per year, their marketing data for the typical buyer carries a lot more weight than your philosophical complaints about using Nimh batteries. Also, there isn't a single manufacturer that gives you upgrades for cost. The profit they make on those upgrades allows them to spend more R&D on the next Prius models to make them better. Toyota has to walk the line between remaining profitable and providing the customers with everything they want. That said, I do really like your screenname. Crapface.

 

Li-x *EVs are the best Toyota's competitors could do, given the NIMH-HSD patent lockup.

 

The A123 prismatic cells require a heavier enclosure because they are pouches rather than hard encased cells. And, be careful of you units, because W/kg is power density. 131 Wh/kg is their energy density.

A123 has already had a battery recall on the Fisker Karma. They lost out to LG for the GM Volt battery program. Hymotion Prius PHEV systems are only lasting 3-4 years. They refuse to sell their products in the retail marketplace. I am an A123 shareholder and yet it is hard to find good things to say about the company.

No manufacturer on the planet has mature Lithium technology that would inspire the confidence required for a mass produced automotive application. It is all an experiment for them right now. It will be a few more years to mass production, and probably a decade to full maturity.

 

The A123System's spec is a typo on my part. As you point out, it's 131Wh/kg. I use their battery as an example because it's not the highest performance lithium-ion chemistry. They sacrifice some performance for safety.

And, of course, several manufacturers, including Toyota, completely disagree with you. The proof of that is all those BEVs, and PHEVs for sale--every single one of them with lithium-ion batteries and long warranties to back up their confidence.

 

Being a LEAF owner, I can't say I share the same opinion: Nissan has dove in with both feet into the lithium pool and is, I believe, banking the farm on its success based on their in-house testing. Notice how Nissan has been struggling a bit of late and then notice how emphatic Ghosn gets when he talks about EVs and you'll catch a glimpse of how important this move is for them. Though their market penetration is so far small, Nissan's commitment and level of support they are offering on these cars is pretty surprising and is one of the reasons why I went for a LEAF (followed more recently by the C as our second car).

That said, check out the LEAF forums where you'll find plenty of griping about that warranty: Nissan only warrants that the battery will provide "sufficient" power output during the 8 year coverage, with no clarification as to how that word is defined. It's generally assumed that if there is a major fault in a battery (only 1 major problem noted so far with many owners over 20K), Nissan will disassemble the pack and replace affected "modules" (4 cells/module). The batteries are designed for this and all LEAF-certified dealerships are required to have this capability. Is this how the Toyota battery warranty works, or do they simply plop in a new pack whenever output is "reduced"? I'd wager they only go this far when the entire battery pack craps out. As a final point on the LEAF, I think it worth mentioning that the wear-and-tear on a hybrid battery pack is much different than it is on a (usually much larger) traction battery pack.

:focus:, I seem to remember reading that the NiMH pack only weighs ~65 pounds to begin with. Why spend $$ more to shave off an extra 20 pounds? Perhaps that is very anti-Prius of me to say, but as designed, the NiMH performance characteristics seem to match well enough with what the HSD can put out (especially for EV mode), so it's not like Li would give you a faster EV speed or longer EV range. Whether less or more wear-and-tear, either technology should get you a roughly 10-year life which I believe is the design life for most cars.

 

^^^
Yep, unfortunately the Leaf's battery warranty includes NO capacity warranty. It's a topic that's been discussed many times on MNL.

This is part of why when (hopefully when), I get a Leaf, I'll almost certainly be leasing. It's the first time I'll have ever leased a car.

 

Nissan, GM, and Mitsubishi already each have over 200 Mwh of lithium batteries in the field, in mass produced cars. Toyota and Ford have each committed to lithium batteries in both phev and evs. Hyundai, BMW, and Mercedes, Renault, VW, Audi, and Porsche use lithium batteries exclusively. It doesn't sound like car companies are uncertain about lithiums future.

 

Li-Ion is the only chemistry that's practical for EV and PHEV right now, and these are low volume cars which limits the risk to manufacturers. Hybrids like the Prii sell in the tens of thousands every month, so for now they'll stick with the tried n true NiMh pack. I'm sure they've tested Li-Ions on the hybrids and found that the weight savings and other advantages to not justify the additional cost... Yet!

 

the prius v or plus in the eu got lithium already...

 

But that's to save weight and make room for the extra seats in the back (7 seater not 5).

I've seen the specs for the UK Prius + and all but one model scrape in below the 100g/km limit - the top of the range model comes in at 101g/km and might not sell in large numbers because of that.

 

pls expain, I do not understand how CARB favors Lion vs. NiMH