Just got my Clarity Plug-In a couple days ago and I have an efficiency question

[Rajiv Vaidyanathan]

Your options are confusing to me.
If HV mode is selected with the HV button, it will operate the engine sufficiently to keep the battery at whatever charge level you started out.
<snip>
I hope I haven't made things more confusing.

Definitely not more confusing. I think you have clarified the key thing I was unsure about. I was not sure whether HV mode would "keep the battery at whatever charge level you started out" or whether it would use battery until it depleted to a preset level (e.g., 57%) before maintaining it at that level.

I assume you meant it will use minimal battery in HV mode. So, there will be battery depletion, but not too much. Because if it kept it at whatever level I started the trip, it would be either running in pure ICE mode (that doesn't sound very HV to me) or would constantly be recharging the battery as it used it (also doesn't sound very sensible).

 

[css28]

Definitely not more confusing. I think you have clarified the key thing I was unsure about. I was not sure whether HV mode would "keep the battery at whatever charge level you started out" or whether it would use battery until it depleted to a preset level (e.g., 57%) before maintaining it at that level.

I assume you meant it will use minimal battery in HV mode. So, there will be battery depletion, but not too much. Because if it kept it at whatever level I started the trip, it would be either running in pure ICE mode (that doesn't sound very HV to me) or would constantly be recharging the battery as it used it (also doesn't sound very sensible).

It will use no net battery charge--this is how hybrids that don't plug in work. On the Volt it's called Hold mode, since it holds the battery at that state of charge--taking a little for accelerating then replacing what it took.

 

[PHEV Newbie]

Definitely not more confusing. I think you have clarified the key thing I was unsure about. I was not sure whether HV mode would "keep the battery at whatever charge level you started out" or whether it would use battery until it depleted to a preset level (e.g., 57%) before maintaining it at that level.

I assume you meant it will use minimal battery in HV mode. So, there will be battery depletion, but not too much. Because if it kept it at whatever level I started the trip, it would be either running in pure ICE mode (that doesn't sound very HV to me) or would constantly be recharging the battery as it used it (also doesn't sound very sensible).

From my experience in HV mode, the computer will switch between all electric, ICE providing electricity for the traction motor, ICE charging the battery (while doing other things), and ICE directly engaging the drive wheels. It can expend quite a few miles in range and then automatically recharge so that you don't lose what you started with. With a good amount of charge in the battery, I've regularly gotten 52-55 mpg on gas alone on the highway in HV mode (going about 60 mph and no loss of net battery charge). With the battery depleted, the mileage seems to drop to 42 mpg in HV mode. I'm speculating the difference is due to the system not having the flexibility to cycle through the full range of modes it would otherwise have with a partially charged battery. My experience might be anecdotal because I usually have a significant charge when I'm in HV mode.

 

[ab13]

Since PHEVs are by nature a compromise, it may be that the EV powertrain won't be as efficient as it is in a pure BEV. But to say that the Clarity PHEV is more energy efficient at highway speeds when powered by the gas engine rather than powered by the battery pack... well, in general and in the overwhelming majority of cases, that's just not correct.

Or, to put it more simply: "Design efficiency" should not be confused with "energy efficiency".
-

This really has more to do with the series hybrid mode of EV than strict EV only mode. Since series hybrid mode can have more losses than the direct drive ICE mode due to additional components in the power path.

The other thing about direct drive mode is that it can add charge in an optimal way depending on what the fixed gear ratio was set to in the car design, since at the correct speed the ICE will drive the wheels and charge the battery at an optimal rpm. The optimal RPM is set by the load from the vehicle speed and regeneration setting of the EV drive motor that the ICE is turning. If you drive faster than the optimal design of the fixed ICE gear than the system will have to draw rather than generate battery power, or switch modes. Which is depicted in the diagrams.

 

[pdxman1]

From my experience in HV mode, the computer will switch between all electric, ICE providing electricity for the traction motor, ICE charging the battery (while doing other things), and ICE directly engaging the drive wheels. It can expend quite a few miles in range and then automatically recharge so that you don't lose what you started with. With a good amount of charge in the battery, I've regularly gotten 52-55 mpg on gas alone on the highway in HV mode (going about 60 mph and no loss of net battery charge). With the battery depleted, the mileage seems to drop to 42 mpg in HV mode. I'm speculating the difference is due to the system not having the flexibility to cycle through the full range of modes it would otherwise have with a partially charged battery. My experience might be anecdotal because I usually have a significant charge when I'm in HV mode.

A 10 mpg improvement? Neither the data nor the explanation for it sounds plausible. Where are you getting the MPG data? Over how many miles was the data collected? I think someone reported a discrepancy between mpg displayed and actual calculated mpg using actual miles traveled and actual gallons of gas i took to fill the tank.

 

[Pushmi-Pullyu]

The other thing about direct drive mode is that it can add charge in an optimal way depending on what the fixed gear ratio was set to in the car design, since at the correct speed the ICE will drive the wheels and charge the battery at an optimal rpm. The optimal RPM is set by the load from the vehicle speed and regeneration setting of the EV drive motor that the ICE is turning.

While I have no doubt that is true, what I have a great deal of difficulty believing is that the onboard ICEngine can charge the battery pack more efficiently (or at lower cost) than drawing power from the wall to charge the battery pack. I don't know if it was in this thread or another that someone claimed the Clarity PHEV was actually more energy efficient when using the ICEngine to simultaneously power the car and charge the battery pack, rather than to just power the car. But at least from the standpoint of theory and thermodynamics, that's flatly impossible. It's a claim that you can get energy or power for nothing. In short, it's a perpetual-motion claim.

I think what's actually going on here is that the Clarity PHEV's "guess-o-meter" is so unreliable that it displays numbers which indicate gains or losses in EV range which bear little or no relationship to the actual kWh gained or lost. What we really need is someone to do proper, controlled testing of the car at various speeds, and test how much kWh was actually used or gained by fully charging the car at the end of each test (and topping off the gas tank at the end of each test), and using an offboard meter to measure how many kWh the car takes to recharge it, as well as using the gas pump's reading to measure gasoline used.

If someone performs such rigorous testing and reports that indeed the ICEngine can both charge the pack and power the car more efficiently -- that is, using less gasoline per mile -- than powering the car alone, then it would be worth considering just how that might be possible. But until someone does such a proper rigorous test, I'm going to continue to assume there is an error being made somewhere. Not necessarily an error on the part of the person reporting the figures, but more likely an error in the numbers displayed by the car's instruments.
-

 

[PHEV Newbie]

A 10 mpg improvement? Neither the data nor the explanation for it sounds plausible. Where are you getting the MPG data? Over how many miles was the data collected? I think someone reported a discrepancy between mpg displayed and actual calculated mpg using actual miles traveled and actual gallons of gas i took to fill the tank.

It's pretty anecdotal. I did two 200 mile loops (other town was about 100 miles away). The average mpg (based on actual fill ups and miles used on my odometer) was over 52 mpg both trips. Granted, this road's speed limits are between 50 and 65 mph depending on the stretch and I stayed within the speed limit. Both times, I had a significant charge on the battery. The only time I drove on EV with the battery spent was a different trip on a faster highway (consistent 65 mph limit and I went 65-70). So yes, I am comparing apples to oranges but I was wondering whether a significant part of the difference could be due to the amount of charge in the battery. I threw that out there to learn if anyone else has the same experience. I should have provided more details.

 

[TomW]

Having driven my Clarity across the country and back, i have beaucoup highway experience but less city traffic experience. When traveling, charging stations are often not available so you might find yourself starting the day with very little HV battery charge. In this case one will experience a whining high rpm ICE, especially if going at high speed or up hill (somewhat unnerving i should add). This is due to the ICE needing to provide power for the car. Putting the car in HV-Charge mode will minimize this whining.

HV-Charge mode has the effect of charging the hv battery up to about 58%
HV mode has the effect of maintaining the current level of charge
HV-Off has the effect of running entirely in EV until the battery is depleted
Econ mode... Still learning about this, but it is not a unique mode. You can use it in conjunction with all the other HV modes.

 

[barnesgj]

Having driven my Clarity across the country and back, i have beaucoup highway experience but less city traffic experience. When traveling, charging stations are often not available so you might find yourself starting the day with very little HV battery charge. In this case one will experience a whining high rpm ICE, especially if going at high speed or up hill (somewhat unnerving i should add). This is due to the ICE needing to provide power for the car. Putting the car in HV-Charge mode will minimize this whining.

Does putting your car in HV mode when there is no charge left in the battery also minimize the high rpm whining? Or does there need to be some charge left in the battery?

 

[Rajiv Vaidyanathan]

So, I used the HV mode for the first time yesterday (so far have always just left it in default mode in the ECON setting and let the vehicle shift modes as needed after battery depletion). I started with 15.5 EV miles of range and it dropped to 14.6 miles after a short amount of driving in HV mode. So, it doesn't fully maintain the charge. Also, my HV range dropped very slightly more rapidly than I would expect (from 178 miles to 165 miles after about 8.5 miles of driving).

Unlike others on this forum, I have not had any issues with the EV and HV range estimates in my first 900 miles. The numbers have seemed reasonable and remained consistent with the driving I do.

 

[css28]

So, I used the HV mode for the first time yesterday (so far have always just left it in default mode in the ECON setting and let the vehicle shift modes as needed after battery depletion). I started with 15.5 EV miles of range and it dropped to 14.6 miles after a short amount of driving in HV mode. So, it doesn't fully maintain the charge. Also, my HV range dropped very slightly more rapidly than I would expect (from 178 miles to 165 miles after about 8.5 miles of driving).

Unlike others on this forum, I have not had any issues with the EV and HV range estimates in my first 900 miles. The numbers have seemed reasonable and remained consistent with the driving I do.

I noticed that David Pogue's display showed an HV range of 458 miles in his instrument panel shot: https://finance.yahoo.com/news/boug...VuOlVT&usg=AFQjCNF9nxFFq_reLrbpsBSDjBrWPWQWgg

 

[Dana Mitchell]

I'm driving mostly highway and using EV exclusively unless I know I'll run out of charge. While I can get slightly better mileage in town with EV mode it is still cheaper to pay for electricity vs gas at 40-45 mpg on the highway. 3.4 cents per mile on electric geting 45 miles on a charge or 4.9 cents per mile on gas at 2.20 gal. In reality I can get better than 45 on the battery and would be lucky to get 45 on the HV mode so it gets skewed even further.

 

[West1]

The theory I read from Honda Accord PHEV owners is to deplete the battery on long trips. Use charge mode to propel the car and charge the battery. Yes this uses more gas. However, a gas engine is more efficient under a heavy load. Yes, during this period you would have used more gas than if you had not been charging the battery. The key is to now understand that after completing a charge, the gas engine is shut off. How much fuel does a gas engine use when off? zero. So you get the next 30 miles or more on EV.

I have also read that this is how the Accord Hybrid functions in some modes. It will almost always be operating with a load on the ICE that is more than it would had been if not for the production of electric.

Of course, your route planning is key. I would not charge the battery with charge mode above what you need to arrive at destination, if i could charge overnight.

This is like the pulse and glide theory. Charge using ICE while driving. Then glide using EV. I would probably choose to charge on long down grade areas. The ICE can be very loud when charge and trying to climb or accelrate/

 

[jdonalds]

I think the general wisdom here is to use EV around town for low speed stop-and-go driving. On the highway use HV mode. Atkinson Cycle engines don't have much power off the line but are great at maintaining speed such as highway driving. Don't let the battery drain. Rather as soon as you enter the highway switch to HV mode and keep a 50% or more charge for low speed driving when you exit the highway.

 

[bobcubsfan]

I stay in EV all the time. Econ mode. If I run out of "juice" on a long drive so be it. The ICE will take over. Having said that, the ICE does kick in during the first few miles I drive. System check?

 

[dstrauss]

I tend to agree with @jdonalds based on both my Clarity and former Prius experience. The Prius engine, like the Clarity, is great at maintaining speeds, just not at getting to them. Overall, EV is much more efficient (in miles per electron) around town at lower speeds. So I switch to HV as soon as I leave the neighborhood and back to EV at my destination. If I can't recharge at the destination i use HV charge mode so can EV around town when I get home.

I've come to this conclusion because EV at freeway speeds suck the battery dry very quickly (I doubt you can get 30 miles at 70-75 mph) so it just doesn't extend range all that much on long drives (mine tend to be 300 miles one way) while I really appreciate the smoothness and quiet in around town driving in EV mode.

 

[bigbug]

It's best if you avoid "charge mode". Just wait until you get home to recharge the car. Not only is this more energy efficient, it also avoids wearing out the battery pack faster than necessary.

So far as I can see, the only good reason to use "charge mode" would be when you're driving into a zone where emissions are restricted, and you want to be sure you can operate in EV mode when inside that zone. Right now I don't think there are any such zones in the USA, but there may be in the future. I could be wrong, but so far as I know, central London is the only such zone at present. We can be sure more are coming.

I've seen some recommend switching to "charge mode" before climbing a mountain, but I don't see the advantage in this. Just use HV mode for that.

Why would charging with engine "wearing out the battery pack faster than necessary"?

 

[Pushmi-Pullyu]

Why would charging with engine "wearing out the battery pack faster than necessary"?

If you're gonna have to run the gasoline motor to produce electricity, it's better to use that electricity to power the motor directly. Using that to first charge the batteries, and then discharge the batteries to run the motor, is not only inefficient and wasteful of energy, it also cycles the batteries for no good reason, which will wear out the batteries faster than necessary.
-

 

[jdonalds]

If you're gonna have to run the gasoline motor to produce electricity, it's better to use that electricity to power the motor directly. Using that to first charge the batteries, and then discharge the batteries to run the motor, is not only inefficient and wasteful of energy, it also cycles the batteries for no good reason, which will wear out the batteries faster than necessary.
-

I don't know the answer but I'll just add that if the car is in HV mode it acts like a regular Prius in that it constantly is charging the battery and using the battery along with the ICE. So for all hybrids the batteries are going through small charge/discharge cycles all the time. It seems like using Charge mode isn't any different except that it may use a stronger charge amperage than normal HV mode. But I'd count on Honda to get that right.

 

[PHEV Newbie]

I don't know the answer but I'll just add that if the car is in HV mode it acts like a regular Prius in that it constantly is charging the battery and using the battery along with the ICE. So for all hybrids the batteries are going through small charge/discharge cycles all the time. It seems like using Charge mode isn't any different except that it may use a stronger charge amperage than normal HV mode. But I'd count on Honda to get that right.

If you watch the energy distribution screen in HV mode, often the flow of energy is from the ICE to the front wheels without charging the battery. If the white gear symbol appears, the clutch has activated to directly drive the front wheels. If the gear does not appear and nothing to going to the battery, the ICE is being used as a generator to directly power the electric motor. Presumably, it is bypassing the battery. In fact, I notice that the ICE is used as a direct generator for the traction motor or driving the wheels directly most of the time. It seems to primarily charge after range is lost (e.g., supplementing the ICE on long upgrades) and it needs to bring you back to the range when you activated HV.

To me, it makes sense to just stay in HV mode during road trips and not bother charging at charging stations. The gas mileage is really outstanding and do you really want to waste 2.5 hours at an out of the way charging station for each 40 minutes of run time (47 mile range at 70 mph)? On top of that, the cost of electricity at charging stations (if not free) tend to be very high, usually much higher per mile than the cost of gasoline.