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Discussion Starter #1
The simplest way to drive the PHEV is to just charge the battery, go as far as you can in all-electric mode, and then start running the ICE and burning gas for the duration of the trip. I’ve been wondering if there might be a better way.

When you know that you’re going to exceed the electric range, it seems like it might make sense to drive in hybrid mode sooner rather than later, and save some of the electric range for certain kinds of driving.

On a recent 84 mile trip, one of the latter legs of the trip went up a mountain highway that requires the car to climb approximately 2000 feet over a distance of a little more than 12 miles. The previous time I drove this trip, I had zero electric range before I started the ascent, and during the last two or three miles of the climb, the ICE seemed to be struggling to maintain 70 MPH and the transmission wandered in and out of lower gears several times. But on the most recent occasion, I drove the first eight miles of my trip in electric mode, and then put the car in hybrid mode. About 40 miles later when I started the steep ascent, the gauge showed an electric range of 18 miles. I kept the car in hybrid mode for the entire ascent and it seemed to perform much better this time, even though I had about 70 pounds more weight in the car. At the top of the mountain, the electric range had dropped to 11 miles, suggesting that the electric motor had been assisting the ICE during the long climb.

After the road leveled out, I put the car back in EV mode and something surprising happened: I drove the remaining 17 miles of my trip in EV mode, and when I reached my destination, the gauge was reporting that I still had four miles of EV range. Not really sure what the explanation is for that, because I had expected the juice to run out six miles before I arrived. Just before I put the car back in EV mode, the fuel economy was somewhere around 47 MPG and when I reached my destination it had climbed to 60.0 MPG, so I’m pretty confident that the ICE didn’t start again on that last leg of the trip.

Some of the strategies I’m contemplating for future trips: save the battery for climbing; use some of the battery at the outset so that it will have room to receive charge from regenerative braking later in the trip; if you expect to be in stop and go traffic, try to either save the battery for that portion, or else try to ensure that the ICE is warmed up when you are doing that kind of driving.

Wondering what other strategies people might have come up with?
 

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The battery is always contributing torque on climbs, no matter the mode, until it drops below some number, perhaps 15 or 20%. That is one of only two ways to get my HEV battery display to drop significantly (the other being flat roads at sub 20 mph).

Yes, if there is a mountain pass to go over, an excellent strategy is to try to get the battery to "zero" at the top, and recharge going downhill. I effectively did just that on a 15 mile scenic drive, half uphill, and half downhill - steep grades and 25 mph. Battery was almost empty at the top, and completely full at the bottom (first and only time the battery display topped out).
 

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Discussion Starter #3
My PHEV only picked up two miles of electric range coming down that same mountain highway the next day (in HEV mode). My experience is that the EV range goes to zero when the PHEV's battery's SOC is 20%. The first time I did this trip (when I had zero miles before I started the climb, so probably 18% to 20% SOC), I didn't think to check the SOC at the top, but I checked it after I had driven another 17 miles in HEV mode and at that point, it was only 6%. My guess is that on that first trip, I reached a point somewhere before I got to the top, where the battery stopped contributing and the ICE had to do it all.
 

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Part of the reason why hybrids do so much better in city driving is that wind pressure of speed is no longer consuming so much power. Consider a mountain pass that you drive over and down at 70 mph. Not so many hills (almost none) that you can go down at 70 mph and gain a lot of SOC. That is because you are pushing through a lot of air pressure at that speed consuming power.

Something to consider when conserving range is more important than time spent driving. The slower you go in any vehicle, the better the efficiency. No bottom limit on pure EV mode, they are more efficient at 10 mph than 20 mph. ICE driving appears to reach a sweet spot around 37 mph constant (ignoring pulse and glide techniques) - meeting an optimal relationship between thermal efficiency, gear ratio, and wind resistance.

One interesting point from my previous example is that my estimated range at the end of that scenic drive was exactly the same as the beginning (plus I gained SOC). Not possible of course (can't drive 15 miles without some real hit on range), but it demonstrates the possibilities of low speed driving. By the way, I came down that hill on cruise control at 25 mph, ICE never came on - 100% regen maintaining speed.
 

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I'm just now getting used to my 2020 PHEV. I've only taken 2 trips that were sufficient to exhaust EV mode. Using my new OBD2 scanner in conjunction with the Torque Pro app, I have graphed the highway section on one of those trips with AC on and cruise set to 70 MPH. The distance variable is continuous and smooth, but the Fuel rate in gal/hr needed some smoothing. Each fuel rate data point graphed, represents a 9 second average with data collected at 1 second intervals. The discontinuities are caused by engine shutting down during which fuel rate goes to zero and MPG calculation incurs divide by zero error. As seen, the MPG averaged around 40 MPG. This seems low to me. Any comments?
HybridMPG.PNG
 

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Thoughts

1. Keep in mind reported range = soc x mpkwh.
Increased reported range (e.g. after descending a hill) can be due to recent increases in mpkwh not soc.

2. Air friction losses at 70mph are double those at 50mph (70^2/50^2). So only 40mpg at 70mph is normal. EPA highway ratings do not assume a steady 70mph.
 

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2. Air friction losses at 70mph are double those at 50mph (70^2/50^2). So only 40mpg at 70mph is normal. EPA highway ratings do not assume a steady 70mph.
Thanks. Yes, I suspected that air friction was the major culprit for lower than hoped for mpg result. I wonder what speed EPA uses in their highway calculation? I'm thinking that next time I exhaust EV, I should run the car around my community ring road at constant 25 mph. That should give me much better result for comparison.
 

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Thanks. Yes, I suspected that air friction was the major culprit for lower than hoped for mpg result. I wonder what speed EPA uses in their highway calculation? I'm thinking that next time I exhaust EV, I should run the car around my community ring road at constant 25 mph. That should give me much better result for comparison.
The EPA test has a max speed of ~60mph and an average of around 50.

Here's a post from a while back about the max EV range for the plug-in. You're correct that 25mph is pretty much the sweet spot.

P.S. try changing your route selection. The Niro can get up to ≈50 miles/81 km on a charge at 24 MPH/40KPH steady state, (I tried that on a track) so if you pick routes that stay closer to that speed, you can get further. 47.4 miles is my record on public roads staying in 25 and 30 mph zones with AC, Radio, and seats OFF, and driving such that my driving style was 98% Eco under the driving style tab in the supervision cluster menu.
 
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Discussion Starter #9 (Edited)
... As seen, the MPG averaged around 40 MPG. This seems low to me. Any comments?
I usually drive highway around 70. I typically get better than 50 MPG on a long trip (I get about 54 if I recall). Sure, I've got something like 26 "free" miles from the battery, but when the trip is several hundred miles, that doesn't make a big difference. I got a little better mileage before I dropped my tire pressure from the mid 40s to the pressure called for by the manufacturer (dealer delivered it with mid-40s tire pressure - apparently that is common). So have you checked your tire pressure? If it's below spec, that would definitely hurt your MPG.

The other thing that I'm probably doing differently from you is that on a long road trip, I only let the EV range run down to about 18 miles, and then I toggle into HEV mode. I make a point to use up that last 18 miles when I'm about 18 miles from home. Keeping charge in the battery helps with hill climbing for sure. I suspect it might also help with stop and go, passing, etc. The Niro will "borrow" from the battery when it needs to in order to meet driving demand, and then pay it back later when it can easily do so. So even if you toggle into HEV mode with an 18 mile range, you might see the range temporarily drop to something like 12 miles (if you're climbing a mountain) and then go back to 18 miles (shortly after you stop climbing). The thing is: the target range that the car tries to maintain gets reset every time you power off the car. So if you stop for gas and you want to keep the 18 mile range, you need to remember to toggle back into HEV mode when you start away from the pumps.
 

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I only let the EV range run down to about 18 miles, and then I toggle into HEV mode.
Thanks. My two trips in which I exhausted EV mode had local traffic at both ends with highway driving in between for the majority of the trip. Maybe if I saved EV for just the local portion where EV does really well, that would make sense.
 

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I too will save charge when I have long distances to travel. A trip to my parents is about 120 miles round trip. I use Hybrid or Sport mode for all the freeway portions going, then switch to EV in town. Coming home, I do the same, except I'll switch over to EV when I know I have enough range left to get to my house. My displayed MPG (which is always a touch high) for the entire trip is usually in the low 60s. I've also made a 250-300 mile trip across the Cascades and back, using the same method. Again, the trip MPG is in the low 60s. So having the PHEV option can make a noticeable difference even on extended travel. And since the majority of my driving is within EV range (especially during the current situation), I'm going a couple of months and only using 1/4 tank of gas. And won't even use that much except the ICE is needed for heat.
 

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...I'm going a couple of months and only using 1/4 tank of gas.
I went a year and two days, just recently filled my tank on Aug 27 - previous fill up was on Aug 25 2019. It was kind of a "perfect storm" in my case: Thanksgiving and Christmas trips didn't happen last year, and then COVID came along and put a damper on any summer fun travel that I might have otherwise done. I was getting a bit nervous about having old gas in the tank for that long - probably not a good thing, even with a semi-sealed tank. But I was also getting nervous about having only a 100 mile range, here in Southern California, in fire season. So when the opportunity came up for an 80 mile trip back in August, I refilled the tank. Nice to see my estimated range back up over 600 miles.

Fuelly reports that my MPG for that previous tank of gas was 193.5 MPG. We all know that this statistic is misleading, because everyone pays for electricity. But in my case, I have solar panels that generate an annual surplus of electricity, and the local utility pays me less than 3 cents per kWh for the surplus (in other words, almost nothing). So to me, it's almost like my electricity to charge the Niro is "free" because the solar panel cost is a fixed overhead that I can't control and I get almost no compensation for the surplus.
 

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Yeah, I drive just enough that some gas gets used. My commute (when I actually go to the office, that is) is 30 miles round trip, with no charging possible at work. And it's often cool enough that heat is needed. I don't think I'd go a whole year without topping the tank off, as the gas is going to get stale and potentially form varnish on various fuel system parts. At least add some sort of fuel additive to help delay any varnish formation.
 

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Discussion Starter #15
As I'm sure you know, older cars had gas tanks that could vent to the atmosphere in order to deal with thermal expansion and contraction. Modern cars have evaporative emissions controls to prevent spewing out gas fumes. So the tank is sort of sealed. But I don't believe that it's 100% sealed and that nothing leaks out (or in). Even if it was designed to be 100% sealed, that's only the design, not the implementation. The owner's manual suggests that you might have to wait for some number of seconds when you go to open the fuel filler door (presumably because it's doing something to reduce pressure or vacuum before you open the gas cap). I don't know what exactly it might do to equalize pressure, aside from venting to the atmosphere, but regardless - I've never had to wait for more than two seconds before the door opened, and that includes refueling in the middle of a long road trip. For these reasons, I don't consider the tank to be 100% sealed. If you have information to the contrary, I'd be happy to see it.
 

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It is 100% sealed for all practical purposes. Easy enough to Google it, all modern cars have this as far as I know.

OK, 100% is not technically accurate for several reasons. Obviously the injector, evaporative system, both of which are pretty darned closed. Also, seems to me I've read that gas can escape from a fully sealed system. Which is part of the reason gas station tanks are double walled. Likewise, seems I've seen gas cans that sit for a while crunkle a bit inward.
 
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