Clarity Issues

Speaking of using little or no gas, how long does the gas last in the tank before it goes stale? How often should the ICE be used to keep the gas fresh?

 

The Chevy Volt is engineered to keep track of the age of the fuel, and to burn it off as necessary to keep the average age of what's in the tank at no more than one year old.

I don't know that this same rule of thumb applies to all PHEVs, but it seems reasonable to assume it does unless the auto maker specifies a different age limit.

 

It is a little different than the Volt. It appears to run ERDTT mode (engine running due to temperature mode) only in very cold weather. If you are familiar with the Volt it had two modes of ERDTT, one that runs when the air temperature reaches 25 F (or 15/35F on newer cars than my 2012) and a second mode that is forced when the battery temp becomes too low. The Volt had an electric heater in the battery so this will never run if you leave the car plugged in regularly.

The Clarity runs more like the second mode on the Volt, and with the seeming lack of heat provided too the pack, it runs a lot when the temperatures have been high in the single digits for the past week with lows down to -21 F. It basically runs as a hybrid car in this mode. It still drains the battery in 25 miles or so, but your gas mileage is much better (it is using the battery for power). However, when it was warmer, say 5 or 10 F or warmer, the gas engine never really ran. I don't believe the gas engine heat is used to heat the battery, although I could be wrong. I say this as they are on separate coolant circuits (there is one for Engine, one for Battery, and one for HV electronics according to manual).

Considering the Clarity is constantly in the ERDTT mode in very low temps (sometimes it comes out if you leave on a trip immediately after charging in cold weather and battery is warm), I think it is not using any external means to heat the battery. Charging is also limited to 4kw or so while it is cold, you can see it slowly ramp up until it is done charging.

The Canadian model seems to have a battery heater, so I am wondering what they think of driving it in extreme cold. I imagine it would be handy to reduce HV mode usage.

 

Both the Volt and Clarity PHEV are parallel hybrids. They can operate in series as well. They can be powered by EV or mechanical power or a combination.

For example:

HybridModes by Eric Tastad, on Flickr

If you look under Engine it says "Propulsion is provided by the engine, coupled through the gears to the transmission" Just like with the Volt, this is selectively blended in at higher speeds to increase efficiency.

I think the revving mode is running the generator for electricity, it revs up so much as it is capable of producing maybe 50 kw in that mode.

If you want to avoid speculating, put up the graph they show in the manual page above that shows where the energy is coming from, it is easy to see where it is getting power from, after some studying of it. It happened to my wife earlier, and I suspect it was from the buffer being low, but it could be a bug too.

 

And here I thought I had read a review that stated the Clarity has no transmission, as there is a direct coupling from the electric motor to the wheels. The gas engine runs the generator that provides the power to the electric motor when the battery is depleted.

The more I read here the more I’m confused.

 

The Clarity PHEV doesn't have a traditional shiftable transmission like an automatic, dual clutch, or manual. It uses a planetary gear set with two motor/generators and an internal combustion engine. Depending on how they load the motors or lock the planetary they can make variable gear ratios (CVT but nothing like belt driven CVT in modern cars).

Many reviewers don't really understand these transmissions, but to me they are the best for parallel hybrids. They allow series operation to make primarily EV with large motors, or parallel for efficiency. The cost is an additional motor/generator.

Some companies like hyundai use their dual clutch automatic, it only needs 1 motor, but has some drawbacks in how it operates and motor size limitations. Both have shown they can be efficient though.

 

What confused me in the review I had read, was that writer specifically mentioned that there wasn’t even a CVT.

My Sonata PHEV had a more traditional transmission and you could feel the shifting.

Now in a car like the Tesla, there would apparently be no need for a transmission with its direct coupling only setup.

 

That is wrong, it does have a CVT, although that leads to confusion with gas car belt CVTs that are totally different. Toyota markets theirs as eCVT.

Yes, Tesla and any BEV are usually single gear reduction. Basically just motor, pinion, and a gear to get to the ratio they want. Very simple. They can use transmissions, but generally don't need to.

 

This makes sense to me. It appears there's still a lot of misinformation out there.

 

Here is a part of a Press release from Honda on December 17th. It looks like the Clarity PHEV does not have a transmission.

Elegantly Efficient Powertrain
The Clarity Plug-In Hybrid utilizes Honda's innovative two-motor hybrid technology, which consists of (1) an ultra-efficient 1.5-liter DOHC i-VTEC® Atkinson-cycle in-line 4-cylinder engine coupled to a starter/generator motor; (2) an ultra-quiet 181-horsepower AC synchronous traction motor; and (3) a 17-kilowatt hour (kWh), 168-cell lithium-ion battery pack.

The Clarity Plug-In Hybrid runs primarily on its electric motor, using its Atkinson-cycle engine and starter/generator motor to generate electricity that is either supplied directly to the traction motor or used to recharge the 17 kWh lithium-ion battery pack. An electric-servo brake system is deployed for regenerative braking, further improving efficiency by using the energy from deceleration and braking to generate additional electricity. It all adds up to an all-electric 110 MPGe (miles per gallon equivalent) combined (city & highway)1 EPA rating.

The Clarity Plug-In operates in three different driving modes, depending on the driving situation, and is able to shift instantly, automatically and seamlessly from one mode to another to optimize overall efficiency:

EV Drive
In EV Drive mode, the Clarity operates like an all-electric vehicle – the engine is off and is decoupled from the drivetrain to reduce friction. Motive power comes from the 181-horsepower traction motor, which draws electricity from the lithium-ion battery pack.

Hybrid Drive
In Hybrid Drive mode, the Clarity functions as a series hybrid. Like EV Drive mode, motive power comes from the electric traction motor. The coupled gasoline engine and generator motor produce electricity, which is sent directly to the traction motor or to the battery pack, depending on the driving situation and the battery's state of charge.

Engine Drive
In Engine Drive mode, which is typically engaged when cruising at medium to high speeds, the Clarity funtions as a parallel hybrid. A lock-up clutch connects the engine (always linked to the generator motor) and the traction motor to send power directly from the engine to the front wheels. Unlike most competing hybrid and plug-in hybrid vehicles, the Clarity does not use a conventional transmission which saves weight and minimizes complexity while improving efficiency.

 

"Conventional" transmission means a shiftable one. It still has a transmission, it is just very different than your typical one.

 

This statement doesn't sound like there is anything other than a lock-up clutch between the engine and the traction motor.
"A lock-up clutch connects the engine (always linked to the generator motor) and the traction motor to send power directly from the engine to the front wheels."

 

Please read number 2. Take conventional transmission to mean Manual, Auto, Dual Clutch automated manual. The Clarity uses a CVT transmission consisting of a planetary gear set, 2 electric motors, etc.

trans·mis·sion
tranzˈmiSHən,transˈmiSHən/
noun

1. 1.
   the action or process of transmitting something or the state of being transmitted.
   "the transmission of the HIV virus"
   synonyms: spread, transferral, communication, conveyance; More
   
   • 
     
     
2. 2.
   the mechanism by which power is transmitted from an engine to the wheels of a motor vehicle

 

PS, it sounds like the Volt, the lockup clutch in the Volt locks the engine directly to the wheels through the planetary set. Based on how the engine behaves I don't know how they would do it differently. A planetary setup is very simple and is how you blend power from multiple sources since you have 3 input or output points you can use to mix power.

The reason I say this is if you watch how the engine works in the clarity it is always at fixed RPM points, it doesn't rev through the range smoothly. This is how CVT's behave, they shift the gearing so the engine can run at a fixed (and efficient) RPM.

The Volt can clutch the gas engine in and out as necessary as there is a clutch between it and one of the traction motors and between the traction motor and the planetary gears. This means the engine can turn the generator only and run in series, or it can link the motor to the drive gears to power the wheels directly. The Clarity sounds and behaves much like the Volt, and having both, I can say they are similar.

Their statement about "Most" hybrids seems completely wrong, as the Prius also has a similar transmission. Many hybrids do have conventional transmissions though, like Hyundai/Kia, etc. Remember, press releases are marketing info.

 

PS, there is a maintenance item for changing transmission fluid in the transmission.

 

I was driving this evening and had this happen to me, too. It was cold, the battery had just recently depleted, and I was driving at slower speeds, like in a parking lot and side roads before reaching the highway. When I got up to highway speeds it seemed to settle down. But it was embarrassingly loud for a while. I had just picked up a person who had never been in the car before but they didn't say anything like, "Hey, is your car ok? It sounds like it isn't running right.", which is what I probably would have said if it was me.

 

Sounds like what the Volt does when it runs out of charge and goes to hybrid mode. The engine whines for 30 sec and then shuts off.

 

Honda America and Honda Canada has youtube videos posted on the modes.

 

The car is smart. It knows it needs to operate the ICE engine for x minutes to complete the warm up period and then get ready to shut off.