e-4WD?

I was thinking more of their extensive investment with Panasonic into NiMH has left them more hesitant to switch to lithium in a bigger way. At this point Li-ion packs will cost them the same or less than NiMH. That or a lower curb weight for the Japanese test cycle requirements has them using Li-ion in the stripper trim for that market.

 

Could be that the NiMH behaves better in low temps?

 

The batteries are in the passenger cabin, and the cabin now warms up faster.
I think it is just because the NiMH packs will have a larger capacity buffer available for emergency use of the eAWD.
A question I always had about the eAWD operation is how is performance effected when it is under constant use and the buffer from the battery is gone? Making it low speed only is a measure to avoid that happening to a driver out on a public road.

 

You have the engine for back-up and the regeneration is improved 28%

MERGED

They are not, they are in an enclosed compartment under the seat and still need fan and cooling duct (though shorter obviously).

 

Yes, but in order to provide power for the rear MG, the power it can supply to the front MG is reduced. Again, Toyota made the system low speed and asymmetrical to avoid 'not enough power' situations.

Pull up the rear seat bottom and you see the pack. Those Priuschatters that got to the first unveiling event did exactly that. That is inside the cabin as opposed to a fuel tank under the seat having the body sheet metal between them, leaving the tank exposed underneath.

The fan and duct are sucking in cabin air, because temperatures comfortable for people are also good for battery operation. Faster cabin heat isn't just a benefit to the passengers.

 

Tel me something new!

 

Source?

I noticed the rear wheels have their own power controller so it draws power from the traction battery. The MG1/MG2 controller is not involved. My concern is it may also provide the 1.5 kW A/C output that I want.

Bob Wilson

 

Why should I pull up the rear seat before driving? And what to do if I have two passengers?
The main reasons IMO for moving the battery to (the enclosed space) under the rear seat are to improve the horizontal location of center of gravity and to make more luggage room.
Slight improvement in cooling/heating of battery due to shorter duct is only small side benefit.
In both cases battery conditioning is is by forced circulation (fan and duct), not by natural convection of air.
Faster cabin heat surely helps - would help also in Gen 3.

 

At any rate, first thing in the morning the battery is at ambient temp. It will take quite some time to warm it up around here! Probably longer than most of my trips! Think about it. Battery starts off at -20 to -30C, trip length is 30 min to an hour. How much will the battery warm up? NOT MUCH!

I thought the e-4wd cars were getting the NiMH battery anyway? It's hard to keep track. Too early to speculate!

 

One data point: the hot battery incident that inhibited hybrid operation ended within a minute or two of turning on the AC. It may be that just having the cool air coming in was enough to enable hybrid operation.

Bob Wilson

 

^^ Well, in case of warming (but not cooling) your battery will warm up also by its operation which releases heat. How much? I don't know.

 

TOYOTA 新型　プリウス 4WDモデルを初設定　１２月に日本市場専用仕様で投入！

 

i suspect we will know more in a month or so... Did they say when will they start sales in the USA?

why would lion pack cost them the same as nimh? I would assume that cost effectiveness of nimh is also getting improved, together with lion. With only 15kg difference, I have no issues with nimh batteries at all. Eco trim is to show off 40km/l so every bit helps there.

As to the e-awd, it has been used for a long time in RX and Highlander. Their on-demand AWD systems (Rav4) also have maximum speed limit at which you can engage "awd" mode, these are not performance awd vehicles but systems that basically help with traction in poor conditions.

It would be cool if it was torque vectoring system like in Acura, but then I guess it would cost a lot more... they are not charging a lot for them in Lexus.

 

And from the battery runs a DC cable to the front inverter. To me it makes sense that the rear motor does not only depend on the battery, but can also be feed from the front MGs.

Btw. as far as I know when electric power is transfered between MG1 and MG2 it's always converted to DC inbetween. If someone has a source that shows otherwise (that 3-phase AC of one MG can be directly converted to 3-phase AC of the other MG), I would be very interested.

Edit: Ok, there are two DC high voltage levels: Before and after boost. Before is battery voltage (~ 201 V) and after is up to 650 V. When power is transfered between MG1 and MG2 then I assume this is done on the boosted DC voltage level. To transfer power to the rear MG it needs to be transposed to 201 V, which makes it a bit less efficient, but still doable.

 

We really need to look at the power electronics schematic, which I do not have handy. However, I can envision power electronics that handles both voltage doubling and the "H" circuit function to reduce switching losses. It certainly be worthy of a paper if not patent protection.

Bob Wilson

 

None. Just pointing out that for the engine and MG1 to power the rear axle it means that there less power it can provide to MG2 and the front.

I am only pointing out that the battery is exposed to the passenger cabin's climate. If it were truly outside the cabin, it would be exposed to the outside air temperatures. It may even require its own temperature control system since it couldn't piggyback of the cabin's.

Through a Scangauge, the battery temps can be monitored on the Escape hybrid. It heats up faster than most expect. With the cylinderical cells, it actually has a cooling system for the pack.

I actually expect the cabin warming up quicker has no real affect on helping the battery warm up.

The cost of NiMH is not dropping as Li-ion has been. Those price drops are due to finding manufacturing efficiencies for larger scale production and improvements in the battery chemistry. Then lithium is simply cheaper than nickle.

Toyota and Panasonic squeezed out those large scale manufacturing cost reductions for NiMH at the beginning of the gen3's run. Then last big technical improvement to the battery itself was the prizmatic cell, which reduced the vehicle cost by not requiring an active cooling system beyond a fan. That occurred halfway through the gen1's run. Small improvements can still be happening, but they are no where near the rate that Li-ion is experiencing. Which in the 5% to 8% range per year since plug ins first became available.

Ford claims Li-ion costs them less than NiMH. Which I find believable, because a quick search over the summer had them both at about $500 per kWh. Toyota pays less than everybody else for NiMH, but the chemistry has plateaued in terms of cost and performance. That might change if a press release from BASF pans out, but that would not have occurred in time for the gen4.

I agree it is a system meant to help in poor road conditions where most will be driving at slower speeds. Someone looking for a replacement to a Subaru, or other vehicle with more a wider operating range of AWD, may be disappointed with it depending on their AWD need.

 

Make up your mind please

MERGED

Disagree.
The battery is in enclosed space isolated from passenger's cabin climate. Without the fan it will not be part of the air-conditioned cabin when A/C is on.
This is probably the best place for battery longevity as it is one of the last places in the car to become hot when leaving the car exposed to sun in a hot summer day.

 

The Toyota transaxle is not easy to master. It took me a couple years before the "Ah HA!" moment. One of the hardest aspects is understanding why MG1/MG2 energy flow reverses around 25 mph:

• < 25 mph - ordinary, MG1 works as a generator providing electrical power to MG2 and any excess needed to add charge to the traction battery. The counter torque from MG1 lets 72% of the engine torque to pass through the mechanical path.
  
• > 25 mph - recirculate (sometimes called heretical mode), MG2 works as a generator providing electrical power to MG1 to serve as a counter force to the engine torque (i.e., think something like over-drive.) MG2 also provides excess power to recharge the traction battery. The counter torque from MG1 lets 72% of the engine torque pass through the mechanical path only the electrical energy comes from MG2.

These very clever and unique operational modes makes the Prius (and all Toyota hybrids) a challenge to understand. MG1 is critical to getting engine power to the wheels via the Power Split Device, the planetary gears. It is simple to explain but hard to understand.

Curiously, I've read one SAE paper from U of Georgia that made impossible claims about inefficiency based upon a 'math' model. Claims that don't bear out in reality . . . like the old analysis claiming bumble bees can't fly.

The easiest approach is to assume there are three transmissions:

• manual - can be single or dual clutch
• hydro-mechanical automatic - usually fairly inefficient
• hybrid automatic - exceptionally efficient because they can move the car with the engine off

Bob Wilson

 

Where does the 25 mph come from? Doesn't it also depend on the engine speed?

We might be getting off-topic here. If you like we can continue to discuss this in the PSD thread I recently started: Power split device and electrical/mechanical power | PriusChat
The thread is for Gen2, but the basic function of the HSD is the same for all generations. At 25 mph MG2 speed for Gen2 is about 1415 RPM. If you like, you can use the value with the formulas in the thread to calculate energy flow for a given engine speed. Or I can do it, if you provide some vehicle and engine speeds. I hope we both can learn something from it. I already learned a lot about the Prius from your posts.