NiMH vs Li-Ion battery - what's the deal?

I think the review has it wrong. The NiMH in the Gen 4 Model 2 is NOT the same as the NiMH in the Gen 3: an improved NiMH technology is used. Sorry, I forget Toyota's name for it.

Of the 5 Li-ion models in the US,

3 have a patch kit:
Model 2 ECO
Model 4
Model 4 Touring (17" wheels)

and 2 have a spare:
Model 3
Model 3 Touring (17" wheels)

 

Toyota is absolutely using the Li batteries to add other options (like sunroof, power seats, and other things that are heavy) while staying in the lower weight class. Toyota is also using spare tires for the same purpose -- that's why models with those options don't have spare tires.

It isn't "manipulation of car weight class", though - lower weight is lower weight, and scales don't lie.

I *hate* to see options such as spare tires unavailable in the higher trim levels - which ironically have other safety options available! So if you want all the active safety features and the spare tire, you can move to the 3, but you can't have NiMH, or any of the amenities in the 4. If you want, say, all the active safety features and power seats and/or sunroof, you can move to the 4, but you can't have NiMH or the spare tire.

 

I like to be a skeptic...are you sure we can rule out manipulation?
The weight class management may also have to do with EPA MPG rating read-across to models in the same weight class.

 

I think it is manipulation, in several ways:
(1) As I get it, Toyota got the Model 2 ECO down to a low enough weight to slip into the next lower weight class, because somehow the formulas would raise its EPA MPG rating.
(2) Then they juggled option weights and spare /no spare to keep all the other models in the next class up. Then among the other versions, they chose for EPA testing the models which would give the highest numbers on the EPA test. Then they submitted documentation that these would be the highest-selling versions (adjusting production to ensure that this would be true). This enabled them to claim the same EPA ratings for all 5 of the other models, so customers would think there was no MPG penalty for going to the higher classes, especially ones with the 17" wheels.

If I understand all this correctly, it seems like exactly what one would do if one is smart and wants to sell cars. I think we all hope that Toyota is smart?

Underneath it all I suspect that the Model 2 ECO is not actually much different from the other models in terms of MPG. It's a rating difference to get suckers like me to buy. But I'm a happy sucker!

 

It's not manipulation of the rules, though, and it's not fraud in my opinion. Lower weight does improve MPG***. The weight of each Prius model is undeniably true, so it deserves to be classified in the weight guidelines set forth by the EPA.

My point is that it's *not* like Volkswagen, who (as alleged by the EPA) manipulated their diesel emissions control software to run their engine lean *only during situations that approximate the EPA test cycle, which are basically impossible to replicate in real world conditions.


***There are also several other modifications made to the 2 Eco, and the reports from the Gen 4 board certainly indicate an MPG boost to the 2 Eco due to these modifications.

 

I agree 100% that it's not manipulation of the rules or fraud. I said it was "manipulation", meaning manipulation (or configuration if you prefer) of the models Toyota produced, not the rules. "Manipulation within the rules" might be a better way to say it.

The VW matter is completely different: they didn't manipulate the rules, they simply flouted the rules. Cheater software had already been prosecuted in diesel trucks, so it was clearly deemed illegal.

 

Regardless, it failed a sale two weeks ago when I tested a Level 3 with TSSP and found the MPG on 5 mile loop at 28 mph returned 99.1 MPG. Good but not good enough.

Bob Wilson

 

Less weight does equal better fuel economy, and on the EPA test, the road load for the dynamometer is based upon coast down tests, which are influenced by the car's weight. I admit, that I have no idea what weight class means for the EPA test. it could just be a cutoff for when a model's trims require their own testing.

On the other side of the Pacific, Japan's fuel economy testing does not use a coast down test to determine the road load. it is based upon what weight class the car falls into, with the dynamometer resistance set by the weight class. The Eco is light enough to fall into the lighter class there, so it is tested against an easier load. While lighter cars should have a lighter load, the Japanese weight class the ECO falls into is also used for cars that can be a few hundred pounds lighter than it. It's not illegal, but does give the car an edge on the test that may not be reflected in the real world.

 

Bob are you saying the cold MPG was too low for you?

 

The car was warmed up and it was 72F outside. I can get 99.1 MPG with our Gen-3 on that test segment and have in the past:

Good, it was not good enough.

As part of this 1,000 mile tank, I would do laps on the loop:


But this graph shows the real problem:

The math model is accurate and the results credible. In a year, the Level 2 ECO will have TSSP and if I don't wind up with a BMW i3-Rex, the problem is solved. Look at the relative performance:

• 117 MPGe - 150 mile range ($28k(?), 6,500 miles) … can reach Nashville
• 56 MPG - 633 mile range ($28k set, 10 miles)
• 50 MPG - 595 mile range (paid, 70,000 miles)

There are technical aspects of the i3-Rex that rule out other plug-ins: city-sized, lack of "B" pillar, rear-wheel drive, 168 hp, tow-bar available, and charge sustaining mode patch. The premium gas and 2 gallon tank is not great but a nice challenge … and I have plans for both. <GRINS>

Bob Wilson

 

If I understand you find the Gen4-Model 3 is only getting 91.8 MPG at 28 MPH so not as good as your Gen3 in this test. Are your results being discussed in more detail on another thread I should be looking at?

 

• Gen-4, Level 3 with TSSP - 99.1 MPG @28 mph, 5 miles
• Gen-3, Two - 91.8 MPG @22 mph, 1,000.8 miles

Bob Wilson

 

Maybe same electric capacity but 2 things remains unknown :
Lifetime NIMH vs LI-ION
Charging capacity (did the li-ion charge faster than nimh???)

 

Wankel, I think pretty much that whole section of the review is gibberish. The two batteries do not have the same "electric" capacity: 0.75kWh is not "the same" as 1.31kWh. And the new NiMH battery is improved over the NiMH that was in the Gen 3. See pages 12 and 13 of this pdf:

 

They have about the same amount of usable capacity with the max and minimum SOC limits in place for long life.

The 7 seater Prius v/Alpha/plus has used a lithium battery since its introduction. So do all the current competitor hybrids. This is about as much time out in the public as NiMH had before the gen2 Prius arrived.

 

Don't know if it has been mentioned yet, but the cost for NiMH is likely as low as it is going to be for Toyota. Li-ion will be cheaper in the future, if they aren't already. But Toyota still has much invested in the NiMH supply chain to just simply switch like the others have done.

 

suposedly Li-ion ages better (in hands of ford, didn't work for leaf buyers): Design News - Automotive News - Why Ford Chose Lithium-Ion for 2013 Hybrids

interesting how someone mentioned in the discussion how Li-ion goes around Chevron's EV battery patents.