Arty101

I don't think Toyota USA is moving towards lithium Ion batteries anytime soon. They'll go to solid state or lithium air batteries as with the world market.

Although I'd like to see it, since when do we get stuff marketed for other countries? And since when was Kansas outside of the US? lol

zes

In a hybrid vehicle, the primary motive force is still the ICE. The battery only stores enough energy to bring the speed down from cruising to zero and then reuse that energy to speed up the car again. NiMeH have sufficient capacity for that with a reasonable weight. Therefore there is no benefit in building larger capacity batteries. The Toyota NiMeH batteries are well proven and therefore relatively low risk both for Toyota and owners after the vehicle gets out of warranty. The Li Ion batteries still have many technical issues including thermal runaway and internal shorting due to irreversible chemical changes. Don't you think Boeing would have put in the best Li Ion batteries money could buy in their Dreamliner? Look at the serious problems they had with those batteries. And Boeing's solution? Put the batteries in a big thick steel box!! I am sure they are saving a lot of weight with that! They should have just chucked the Li Ion battery and put in a NiMeH battery instead. At least it is safe and proven technology.

I think Toyota is very wise in not getting rid of NiMeH batteries until Li Ion is proven in the long term in real life. That will take years. Toyota/Lexus has very precious reputation of reliability on the line. It ill take just a few failures to damage that reputation, and they don't want to risk it, especially when the benefits are limited in hybrid vehicle use.

Li Ion make more sense in all electric vehicles, where total capacity matters, but that is another story.

chromedome

Yes, the common lithium chemistries do have issues with thermal runaway, but the higher energy density to me is worth the risk. Toyota are being very conservative but this could make their vehicles less attractive to future buyers. German plugin hybrids are using lithium cells for much longer electric range while allowing the use of more powerful electric motors. Check out the Passat GTE, on paper it would spank the ES while costing less.

But that's also on paper whereas VW real world reliability isn't great, especially when you add a small turbo engine and dual clutch box to a hybrid system. The ES sits at a sweet spot on the pricing/efficiency/weight matrix but not for long. A plugin ES with enough range for short daily commutes would be perfect.

Arty101

Yes, a plugin ES would be perfect. That said, does the plugin Prius use Lithium batteries? If so, than why not a plugin Lexus?

Canesguy

Not necessarily, my Accord Hybrid has Lithium, and it gets 48-52 mpg vs. the 37-41 I get with my 300h (these are actual calculated figures at the time of fill-ups).

zes

I think this is due to the fact that the HAH has a different, more efficient hybrid drive system, not necessarily the batteries. The capacity of the traction battery in the HAH is probably very similar to that in the 300h .

Canesguy

Could be, but then it has better mpg despite it's lithium battery, and refutes the premise of worse mileage with lithium.

chromedome

I think the Accord gets better mileage mainly down to that transmission-less drivetrain and slightly lower weight. I'll throw in a Ford Fusion hybrid for comparison.

Power:
Fusion - 2.0 L 141 hp engine, 118 hp motors, 188 hp total
HAH - 2.0 L 141 hp engine, 166 hp motors, 196 hp total
ES300h - 2.5 L 156 hp engine, 142 hp motors, 200 hp total

Battery:
Fusion - 1.4 kWh lithium ion
HAH - 1.3 kWh lithium ion
ES300h - 1.6 kWh nickel hydride

Weight:
Fusion - 1670 kg
HAH - 1617 kg
ES300h - 1705 kg

zes

The motor will not know if a NMH battery or a LI battery is powering it. The type of battery should have no impact on mileage. HAH has a smaller ICE and that gives it better mileage, at the expense of some more noise. 100 kg in weight is insignificant.

chromedome

I just passed a weigh bridge at a highway entrance and my ES300h showed 1740 kg with two adults onboard. A 100 kg difference with the Accord would affect acceleration but fuel consumption? Not so much. The Accord gets lower fuel consumption by minimizing drive train losses. The engine behavior might be a bit weird but 52 mpg is worth the price of that oddness.

The battery capacities for these hybrid sedans are similar. I think it comes down to a sweet spot in the cost/weight/efficiency matrix. The ES can afford to use a larger, less dense battery pack because there's a lot of space available and there's also a lot of weight to haul around. The Accord and Fusion use lithium ion cells to minimize space used up in the trunk. Interestingly, Tesla data from their Roadster program shows that lithium ion cells have acceptable performance after many years, so maybe Toyota are being too conservative by sticking to NiMH.