Using HV Charge

[sniwallof]

I think where HV charge may show a hit to economics would be the following example:
1) Run in EV mode until ICE starts (2 bars on battery for most of us)
2) Fill the tank with gas and record odometer reading
3) Leave gas station and put car in HV Charge mode
4) Drive until battery is back to about 50% charge
5) Put car back in EV mode and drive until ICE starts (2 bars on battery)
6) Refill tank, record gallons gas burned and calculate miles driven from previous fillup - Calculate mileage as Miles driven/Gasoline burned

It might be best to add changes in elevation? So, maybe do that same test in both directions? Then maybe a bunch of times? So, it's a LOT of work unless it happens to match someone's normal daily travels, someone who is also willing to the extra work on a regular basis, which is probably a lot less fun than it sounds.

The few test runs I did surprised me, coming from lore in the Volt forum on such matters, I thought by definition that using the gas generator as part of an energy cost driving routine would be terribly inefficient and relatively high cost. The data I got was barely above anecdotal, but surprisingly good, still some loss by the extra conversion, but no where near as lossy as I expected.

Beyond just playing by pushing buttons (sometimes unnecessarily, which I enjoy way too much), I think the only time I've somewhat seriously used hv charge is when I left the rest stop on the thruway and forgot to push hv. That seems to be a common thread problem [hello HONDA if you are listening ], not sure what the fix is beyond @insightman 's sticky reminder. Maybe there could be a way to change the default to start in hv for highway trips, but then you have to remember to set it back to EV. Or, above 60 mph for more than 5 minutes Siri, Alexa, (or equivalent), could come on and say, "You seem to be driving on a highway, would you like to save your EV miles for around town, and switch to hv now?"

 

[Ray B]

I think where HV charge may show a hit to economics would be the following example:
1) Run in EV mode until ICE starts (2 bars on battery for most of us)
2) Fill the tank with gas and record odometer reading
3) Leave gas station and put car in HV Charge mode
4) Drive until battery is back to about 50% charge
5) Put car back in EV mode and drive until ICE starts (2 bars on battery)
6) Refill tank, record gallons gas burned and calculate miles driven from previous fillup - Calculate mileage as Miles driven/Gasoline burned

Good plan. I would add that it would be advisable to have an ODB II reading of the SoC% as "0 EV" with two bars on the battery gauge can be anywhere from 10 - 15% SoC. If you start the test and end at the same SoC%, the result will be a little more accurate.

 

[Ray B]

I will add that my charging/driving routine is built around the concept of being gentle on the EV battery to make it last as close to forever as I can. So I tend not to charge to 100%, and I also tend to not let the EV drop to 0. Of course, I do have both 100% charge and 0 EV happen from time to time, but only on rare occasions. So when I have a lot of errands and I know the level will drop to 0 EV without intervention I am now reverting to HV CHARGE to get me by with enough EV miles. Of course, I could just run in HV mode, but when stopping and restarting the car I usually forget to re-engage the HV until it is too late and I hit 0 EV. Also it is no secret that each restart resets the EV SoC% setpoint in HV mode, so it becomes kind of inevitable to avoid 0 EV at times.

It is not an anxiety, but just what I have convinced myself is a 'best practice' to use the battery in the middle of its range and thus artificially increasing the buffer at the top and bottom ends. The HV CHARGE helps me to to keep it in this happy range.

 

[Dan Albrich]

=Maybe there could be a way to change the default to start in hv for highway trips

My take is simple. Have the car automatically go back to its last mode, whatever that was. So if HV was engaged last drive, then HV is still engaged. And yes, still simple to change modes. This would allow folks on a long trip to select HV, and leave HV. Then when home turn off HV, and leave it off.

I dislike that it resets to "HV-off" every time I start.

 

[2002]

My take is simple. Have the car automatically go back to its last mode, whatever that was. So if HV was engaged last drive, then HV is still engaged. And yes, still simple to change modes. This would allow folks on a long trip to select HV, and leave HV. Then when home turn off HV, and leave it off.

I dislike that it resets to "HV-off" every time I start.

Probably the only time it might make sense for it to automatically revert to EV is after charging. But if you manually place it in HV mode you are telling the system that you want to maintain the current SOC, until instructed otherwise. If you then stop somewhere and shut off the car, but you don't charge, why would it assume that you no longer want to maintain SOC?

 

[insightman]

Probably the only time it might make sense for it to automatically revert to EV is after charging. But if you manually place it in HV mode you are telling the system that you want to maintain the current SOC, until instructed otherwise. If you then stop somewhere and shut off the car, but you don't charge, why would it assume that you no longer want to maintain SOC?

I expect the automatic reversion to non-HV has something to do with maximizing the Clarity's EPA gas-mileage rating.

 

[Hoon]

I expect the automatic reversion to non-HV has something to do with maximizing the Clarity's EPA gas-mileage rating.

That’s what I’m thinking too. My MINI 2015 Hardtop was also always set to go back to mid mode (from three choices). Later I read there is a way to change the parameters stored in the ecu to allow keeping the memory of last used mode along with other settings. Being a Mini, most people used that to stick it in Sport mode all the time. I wish Honda had something like E-SYS in BMWs.

 

[Ray B]

I tried a HV Charge MPG test this evening but it didn't work as well as planned.

Full fuel tank
SoC at Start of test = 18%
Roads travelled = local roads at 30 - 40 mph (probably 35 mph average; red lights, stop signs, light/moderate traffic)
HV charge for 10.5 miles (added 18.1 miles of estimated EV range).
SoC at HV Charge finish = 43% (25% added)
Total miles to return to 18% = 27.0 (10.5 on HV charge + 16.5 on ECON/EV)
Gas required to fill up = 0.389 Gallons

MPG = 27.0 / 0.389 = 69.4 mpg

I didn't have the time or inclination for a longer test, but anyway, to go from 0 EV (~12% SoC) to 58% would probably use < 1 gallon, so it may be tough to get a valid result depending on the nature of the gas station pump; I tried to fill at the exact same pump both times but it was occupied on the refill so I used the same pump but the nozzle on the other side of it.

So the test would probably need to be repeated with a longer spread in the range in order to get some more gas drained, but I think it will still have a lot of variability this way. The logical approach would be to keep HV charging over and over until the tank is depleted and just total up the miles at the end of it and refill the 7 gallons. I'm not sure I have enough curiosity to follow through with it.

 

[David Towle]

Yeah tough to get a good number from that small an amount of gas. That's a lot of miles EV range added per mile of HV Charge, probably ideal conditions for doing it. I hope you do have the curiosity to do it for something near a full tank!

 

[David Towle]

I did a comparison test of 2 different methods of driving without plugging in, and relying on HV Charge, making sure I always had enough electric range to run local multiple 1-2 mile errands in EV mode (and I never push the pedal far enough to turn the engine on while doing these). Both test involve full tanks, more than 6 gallons. I started and ended each test with 10 miles of range so no corrections to measured miles were needed. Both these tests involved 90%+ highway driving.The 2 methods and their results are as follows:

1. Alternating between HV Charge and EV. Starting with 10 miles range, I would run HV Charge until it shut off, then go to EV mode to use up what I generated. I made sure each time I got off the highway I had the full 35 miles or so EV Charge would allow, and also did recharge on longer off-highway errands on local roads. I did this because I assumed HV Charge would be more efficient at lower speeds where the car would not have gone into gear mode anyway due to low speed. Method 1 never allows gear mode to be invoked. Using this method I got 46 mpg.

2. The second test was what I assumed would be more efficient. I again used EV for local errands, used HV Charge on longer off-highway runs, and on the highway used mainly HV mode except when I knew I would want to use EV when I got off the highway (so I would use HV Charge then). So of course a lot of the highway HV miles were in gear mode. With this method I got 49 mpg.

These test show to me that HV Charge is quite efficient no matter how you use it, so don't shy away from it if you need it to keep up the charge. An advantage of both of these is the engine does not cycle on and off as much as it does in HV mode. However method 1 would probably be useless in the winter due to excessive times with no engine heat available. I think the primary difference between the MPG of the two tests is the availability of gear mode in method 2.

Sorry I don't have any OBD outputs to fully illustrate what I did, that's beyond my capability.

 

[Landshark]

What if you started HV+ with 0EV, set Trip B to 0 and run until the battery is at 58%? Or HV+ shuts off. Then looked at the Trip B data?

That should give an idea of mpg while in HV+.

 

[Ray B]

I did a comparison test of 2 different methods of driving without plugging in, and relying on HV Charge, making sure I always had enough electric range to run local multiple 1-2 mile errands in EV mode (and I never push the pedal far enough to turn the engine on while doing these). Both test involve full tanks, more than 6 gallons. I started and ended each test with 10 miles of range so no corrections to measured miles were needed. Both these tests involved 90%+ highway driving.The 2 methods and their results are as follows:

1. Alternating between HV Charge and EV. Starting with 10 miles range, I would run HV Charge until it shut off, then go to EV mode to use up what I generated. I made sure each time I got off the highway I had the full 35 miles or so EV Charge would allow, and also did recharge on longer off-highway errands on local roads. I did this because I assumed HV Charge would be more efficient at lower speeds where the car would not have gone into gear mode anyway due to low speed. Method 1 never allows gear mode to be invoked. Using this method I got 46 mpg.

2. The second test was what I assumed would be more efficient. I again used EV for local errands, used HV Charge on longer off-highway runs, and on the highway used mainly HV mode except when I knew I would want to use EV when I got off the highway (so I would use HV Charge then). So of course a lot of the highway HV miles were in gear mode. With this method I got 49 mpg.

These test show to me that HV Charge is quite efficient no matter how you use it, so don't shy away from it if you need it to keep up the charge. An advantage of both of these is the engine does not cycle on and off as much as it does in HV mode. However method 1 would probably be useless in the winter due to excessive times with no engine heat available. I think the primary difference between the MPG of the two tests is the availability of gear mode in method 2.

Sorry I don't have any OBD outputs to fully illustrate what I did, that's beyond my capability.

I used a similar approach to your method #1 for the past 8 days on mostly suburban roads (10% highway) and got 47.9 mpg using HV charge (258.4 miles / 5.4 gallons). Started and ended at the same battery SoC.

 

[David Towle]

I used a similar approach to your method #1 for the past 8 days on mostly suburban roads (10% highway) and got 47.9 mpg using HV charge (258.4 miles / 5.4 gallons). Started and ended at the same battery SoC.

Good info, the mpg is exactly what I would expect since you were at slower more efficient speeds where gear mode does not come into play anyway. I just did another 90% highway tank with method 2 and got 49 again.

Coming up on my one year anniversary with the car with over 22,000 miles. One reason I'm driving so much is I don't feel guilty about wasting fuel when the mpg is so good.

 

[Landshark]

FWIW: The manual does not recommend using HV+ in city or stop and go traffic. Sustained highway speeds are the preferred method.

I have done only one experiment with HV+. This was in the middle of a long drive. After depleting the batteries to 0.0 EV range and then driving in HV mode for a few hundred miles, HV+ was deployed. It ran for approximately 1/2 hour and brought the battery level up to ~50%, at which point it was turned off. Speed was steady at ~75mph. At the time I was unaware that the SOC is restricted to 58% using HV+. Otherwise I would have just let it run to 58%.

MPG for that segment was ~25. The total MPG for the 700 mile trip was ~40, including the 25mpg segment.

By my calculations, on HV+:
1/2 hour at 75mph covered 37.5 miles.
37.5 miles at 25mpg consumed 1.5 gallons.

Without using HV+,
37.5 miles at 40mpg consumed .94 gallons.

An additional .56 gallons was consumed to restore ~25 miles of EV range, compared to driving in HV mode.

On the surface the amount of fuel used to gain EV range appears to be a wash. I actually found this to be a surprise and will have to do further testing to convince myself that it is accurate.

Is it cost effective? That will depend on fuel and electricity prices for each driver. Or a willingness to burn fossil fuel to save money rather then go green at greater cost. Currently in So Cal, gas is above $4/gal, so it would cost over $2 in gas to get 25 miles of EV range using HV+. For less than $2 I can fully charge and have been getting 50-60 miles on EV.

Another item to consider is that HV+ is a direct DC-DC charge. It may not be exactly the same as Chademo/Level 3 charging, but my understanding is that it is similar. There is some discussion that this method of charging could shorten the life expectancy of Lithium batteries. This may be why Honda limits SOC to 58%. It also prevents a driver from being able to use the full capacity of the battery.

 

[David Towle]

I'll have to look up what the manual says about country road driving 30-50 mph that's where I've been doing a lot of my charging. Not using method 1 anymore, just getting enough charge so I can use the car in EV for local errands.

I've also found it to be almost a wash, it is a pretty efficient system.

My economics are very different, $3.30 for 15 kw vs $2.40 for a gallon of gas. And as I mentioned earlier I'm trying to not make my solar system look undersized in case we decide to sell the house.

I agree with you about battery life, this system charges the battery very fast under some conditions. I will throw in a regular full wall charge once in awhile.

 

[Dan Albrich]

I've used HV charge a lot. No problems. To its credit, HV charge works even going over tons of small up and down hills, and including through mountain passes. The car does everything just fine. When you're really cranking up a mountain, even with HV charge enabled, the EV range will not increase. Or if it does, it will increase very little. But when you reach a plateau or even a brief down-hill or flat region, you'll see it start increasing the stored charge until 58%. It does build charge slowly in my experience.

On long trips I don't worry at all about gas mileage, and I never plugin to charging on a trip. I do not ask my family (most of whom have zero clue about electric or partially electric vehicles) to let me plugin. So I go 100% gas, and if need be hit HV charge if my EV range is depleted. I do, as noted here, still get great gas mileage. So yes, in part HV charge is what has allowed me to do multi-thousand mile trips with no hassle, and no need to plug in.

In my brain, I know a full-charge might cost my family member about $1.60 if I need a full charge (The locations I visit have 11 cent KWH). I would not hesitate to ask a family member for $2 or less for help on a trip, but folks who are not savvy simply do not know what you might be asking. They have no way to quantify it, and if their house is old and electrical systems not up to snuff, you don't want to worry them by potentially throwing a breaker even for 110v charge. Anyway, I simply don't ever need to ask, and that's just the way I like it. The car manages itself, and even if I forget to press HV and need a charge, I can do so while driving down the highway.

Also - I now have SB 18-097, but the only super horrible experience I ever had with this car was charging at a very remote (Crater Lake NP, Oregon) EVSE. I simply *never* need to charge away from home and now absolutely refuse to do so. That problem really made an impression on me. Charging away from home, for me, is way not worth it. I average 40 or more MPG which is way better than my last car. Anyway, I feel no need to try and do better than that while away from home.

 

[Geor99]

I agree that in theory using charge mode followed by EV to use the built up charge should be less efficient than just using regular HV. But we have heard anecdotally on this thread and other threads that it is apparently not that much less efficient. The tests we hear about are always very limited, in many cases just based on one test run, and sometimes the tests claim that HV charge is equal to, or as claimed in a couple of other threads even more efficient than regular HV. Of course it's easy to dismiss limited test results, but I think they are useful in providing at least preliminary data, even factoring in the uncertainty of the limited tests they do point to charge mode as being at least in the same ballpark as regular HV and not wildly inefficient as we have sometimes assumed.

This is different than what I have read about Prius Prime where people do report charge mode as being noticeably less efficient. But Prius Prime has a more elaborate "real" CVT system and some clever gearing which allows the gas engine to directly power the wheels at pretty much any speed. So with Prius Prime using the gas engine to generate electricity is almost always going to be less efficient than directly powering the wheels.

Clarity on the other hand went with a much simpler and presumably lighter weight transmission where the gas engine only has one gear available to directly drive the wheels, and so it is only used at certain speeds and power demands. Most of the time the Clarity gas engine is powering the wheels through the electric generator. Not as efficient as direct drive but I am guessing that they decided that the tradeoff is worth the cost and weight savings of having a full transmission. Especially since for in town driving people will be using a lot of plug-in EV, and on highway trips the steady speeds will make gear mode available much of the time.

So what we are left with for the most part is just losses from storing and retrieving electricity using the battery, compared to using the electricity immediately to drive the wheels. Presumably above 58% charging becomes less efficient which is why HV mode is restricted to SOC below that range. But in the range where it is allowed the losses are presumably minor.

More elaborate and accurate tests would factor in gear mode, i.e. test runs at speeds that in HV use gear mode a lot, then do the identical test run using a combination of HV charge and EV.

But I think based on the limited data that we have so far, charge mode is probably only slightly less efficient than regular HV, however not enough to worry about if wanting to use it for aesthetic reasons, like reducing engine noise on a hill climb, or wanting to have EV range available at your destination, especially when you forget to place a sticky note on the dash reminding you to turn on HV when you leave the rest stop.

What is Gear mode?

 

[Landshark]

What is Gear mode?

That’s when the gas engine is directly driving the front wheels. Typically when the engine is running it is powering a generator that provides electricity to the motors.

 

[MPower]

If you have the info screen up on the tablet you can see a teeny tiny gear icon at the intersection of the battery, ICE, and wheels power flows when you are in gear mode.

 

[jdonalds]

If you have the info screen up on the tablet you can see a teeny tiny gear icon at the intersection of the battery, ICE, and wheels power flows when you are in gear mode.