Energy flow between gas engine and battery in Kia Sorento PHEV
Justin Hart's picture

Kia Sorento Plug-in Hybrid Drive Modes Continue to Mystify

I am getting closer to an answer. However, I am still a bit puzzled by the way the 2022 Kia Sorento PHEV decides which mode, hybrid (HEV) or electric (EV), to operate in when I have placed the vehicle into the Auto mode.

Today I performed a new test, as described in a previous article. I drove a roughly 23 mile loop (22.3 miles) twice, once in Auto mode (which leaves it up to the vehicle to decide whether hybrid or electric propulsion is optimal), and once manually selecting between the two. I did this after my first test yielded surprising results; the vehicle stayed in electric mode when I figured it would switch to hybrid. After my second test, I am surprised yet again though this time I feel like I have gotten closer to understanding exactly how the Kira Sorento PHEV “thinks”.

Here’s what happened: On the first loop, in Auto mode as soon as I pulled out of my garage, I started on my route to the freeway (.7 miles from my house). At the crest of a steep hill halfway to the freeway, there’s a stop sign. When I was pulling away from the stop sign, the gas engine suddenly fired up. I looked down at the instrument cluster to check and the car said I was still in EV mode and Auto was showing (and the battery was fully charged!). There was no illuminated “HEV” light to be seen. What was going on?

I coasted downhill most of the rest of the way to the freeway. The gas engine kept running (even though I was coasting). This was totally unexpected, and I wondered why it happened. I think it is probably because I mashed the accelerator down a little too hard on that steep hill at the stop sign. Once the gas engine comes on, it may not shut down right away if the engine block is cold and it was since I hadn’t started the engine before. This makes sense as it would protect the engine from lots of short duration operation, which can wear it out faster.

I came to another stop sign just before the freeway, and then the engine turned off. I glided on electric power onto the onramp, which heads down a long hill, and mashed the accelerator to get to 60 mph before the end of the onramp, which is about a quarter mile down the road. Doing this turned the gas engine back on and that is when I may have distinguished an important part of the Sorento’s decision making logic. Technically, I am guessing, but I noticed when the tachometer needle (right side) touched the second peg in the “Power” band, that is when the gas motor woke up. Below is the point on the tach I am referring to and I think, but will have to test another day, that regardless of which mode the Sorento is in (even in EV mode), when it hits this mark the gas engine comes on:

2nd peg in Power band of tachometer

On with my first loop! The Sorento switched into hybrid mode just before I merged onto the freeway. Traffic was slower today with lots of rubber banding. There were multiple sections on the freeway where 30-40 mph was as fast as I could go. After about 4 miles, it opened up, but the vehicle remained in HEV mode throughout. Also, I noticed that the gas engine warmed up very quickly (via the temperature gauge). Only 8 minutes into the trip and it was already close to optimal temp (1/4 of that in EV mode). I assume that, by design, the gas engine will quickly reach optimal temperature.

The loop included about 11 miles of freeway driving and I hit speeds of up to 75 mph, briefly. I then exited to a 2 lane 40-50 mph highway that goes between two small mountains. There was no traffic to speak of on these roads, so I drove the speed limit or a couple clicks over the rest of the way home. What surprised me here, just as it had as I started out, the gas engine remained on almost the entire way, even when coasting! I could get it to go to sleep sometimes by coasting for a tenth of a mile or so and then very gently pressing on the accelerator, but once the tach got about 1/3 of the way through the “Eco” zone, the gas engine came back on. It felt like the Sorento PHEV was taunting me. You think you’re smarter than me? I’ll show you! Regardless, even though the first loop, in Auto mode, was done mostly in HEV mode, I still got pretty good gas mileage:

Kia Sorento PHEV instrument cluster showing fuel economy

48.4 miles per gallon, in a 6 seat SUV/family hauler is nothing to sneeze at. But still, I felt like the Auto mode had let me down. I knew there had to be a way to do better.

Loop 2 was actually done several hours later, just as it was getting dark a little after 4pm in Seattle, these days. The temperature outside was still in the upper 50’s (61 when I did the first loop), in December, in Seattle. The world is turning upside down I tell you! It feels like September out there. I intentionally kept the PHEV in EV mode until about 4 miles into the test in order to better simulate how I would use it on a longer trip. I want to use up enough of the battery at the start so that I can fully capture braking and coasting regeneration; if the battery is full when I go into hybrid mode, I’ll miss some or a lot of that “free” electricity.

At 4 miles I switch to HEV mode and drive the next 7+ miles on the freeway at speeds between 60-75 mph. When I exit the freeway and come to a stop at the end of the offramp, I switch back to EV mode. Traffic is much heavier here this time through the loop and it takes about an extra 10 minutes to finish the drive. My 9 year old daughter is really going to enjoy this. That’s not sarcasm by the way. She is in the middle row behind me, with nothing to play with or occupy her mind besides the “chill” house music on the XM radio station I tuned in to. “Turn up the radio please!” she says, and proceeds to call out her kitten’s name to the steady beat of the music. Note, she is doing this because the kitten’s name is Chili, and she thinks that’s the name of the radio station. See, traffic isn’t always such a bad thing.

Not surprisingly, the Sorento stays in EV mode the rest of the way home. I am being careful not to punch the accelerator, and the vehicle has adequate power to make it up hills without need of gas assist as long as you aren’t laying into the pedal too hard. I get home, and sure enough, I am smarter than my Kia Sorento PHEV, this time:

Kia Sorento PHEV instrument cluster showing better fuel economy

151 mpg, with a kid in the back seat and the headlights on and the house music thumping, is much better than 48.4 mpg. So, not that I have definitively figured out how the algorithm in the Kia Sorento PHEV works in Auto mode, I have gotten closer. Hey Kia, would you be open to providing us with more specific information on how your PHEVs decide when to be in HEV or EV modes?

Until we might hear from Kia, additional tests may have to prove things out and I am planning my first real road trip for more testing, after I can get a shattered window replaced on my Sorento (thanks criminals!). Here’s how I think it works though: There is a speed at which the gas motor will come on and I believe it is around 75 mph (I read this online, but haven’t tested it yet, technically). There is also an accelerator position or tachometer peg at which point one can also force the gas engine to come on (see my first photo, above). This sounds familiar. I read in a European Kia PHEV user forum that someone had heard from Kia Italy, regarding the Kia Exceed PHEV, that speed and accelerator position are two factors. If that is true for the Sorento, that means there are also road conditions that might encourage the Kia PHEVs to turn on the gas motor (something else I will have to test the first time I take it offroad or in the snow I guess). We’ll have to keep testing for now. Please leave any feedback or your own testing results below in the comment section.

Justin Hart has owned and driven electric vehicles for over 14 years, including a first generation Nissan LEAF, second generation Chevy Volt, Tesla model 3, an electric bicycle and most recently a Kia Sorento PHEV. He is also an avid SUP rider, poet, photographer and wine lover. He enjoys taking long EV and PHEV road trips to beautiful and serene places with the people he loves. Follow Justin on Twitter for daily KIA EV news coverage.

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I actually work for KIA here in North Carolina and we have a customer experiencing the same issue. I'm going to have my Service Manager look into this tomorrow and hope to have more information.
I would be very interested to hear what your Service Manager says. But, just to be clear, are you referring to my “issue” with figuring out the algorithm or behavior of the Sorento PHEV in Auto mode, or my smashed out rear passenger window? The window is my only real issue (not that it’s an issue with the vehicle... just a very long wait for parts... going on 3 months now). The behavior of the car is just interesting and a topic that I know many other owners/prospective owners are curious about. :)
I too have a 2022 sorento phev and trying to figure out the algorithm. I wish there was a way to adjust how aggressively it used the battery in HEV mode. I don't have a charger at home and when I charge in town by the time I get home the battery is nearly depleted. Interested to see what you find out.
Me too! I will certainly be experimenting to see if I can’t manually control how much it uses HEV mode when there is sufficient charge in the battery to still drive in EV mode. If I were in your scenario I might try putting the car in EV mode to start, then switch it to HEV mode after getting on the highway/the fastest section of my drive home, and then switching back to EV mode when exiting the faster section or highway. But if that’s most of your route, maybe that won’t make a difference.
I have a 2022 sorenti preview and want to know when I take my trip to the mountains next week what is the best mode to go in. I drive 45 miles to work everyday and having charging stations where I work. So ev mode is way best for this. I guess I want to know how do I know what modes to use?
Hi Glenn! Will you have a full load of people and or cargo? Are you towing anything? Assuming you are not already taxing the vehicle with a full load, you might be fine just keeping it in EV mode as you do for your commutes. Of course going up a mountain will drain the battery faster, and not knowing how far you’re driving before you get to the upward part of your mountain drive I would suggest the following: 1. don’t use up all of your battery charge first, you might need it for a boost if the mountain passes are steep or long. Maybe keep at least half your EV range “in reserve”. 2. Regardless, if the pass is very steep or long and you need more power to maintain speed, put it in Sport mode. This will be less fuel efficient, but there is no way around that, going uphill is always less efficient. It depends on whether you need extra power or not though. If the mountain pass isn’t too steep or long, you may not need the Sport mode. If you have 4 adults in the car with you plus a load of stuff, you may want the Sport mode regardless. It’s your friend when you want more power... and note when the gas engine is producing more power than it needs, some of that will go back into the battery for “storage” too. :) Good luck and travel safe!
I would use automatic mode for your mountain trip. I drove from Idaho to Colorado through a fair amount of mountains and it did great. Went 700 miles and still had a fair amount of battery left over so I used ev mode for the last 20 miles.
Hi Glenn. I went over few longer trips recently (far behind the battery range) and to mountains with fully loaded car as well. There is this one - poorly described in manual feature - AUTO mode. From the observations I had, in this mode car is using battery more than in the HEV mode, but definitely not all the possible time as in EV mode. Somehow it calculates the driving conditions and switches into EV mode only when it can have biggest impact on overall driving efficiency (or at least so far I believe so). With this mode it could easily happen, you will have 80% battery even after 100 miles, based on the road type and driving style. Maybe give it a try and when you are getting closer to your destination and there is still some juice in the battery, switch it then to EV to get maximum from the battery range (we don't want to come to destination with battery still charged, do we?). Once the battery reaches some level (in my case it varies between 12%-20% based on the conditions) it is then automatically keeping car in HEV mode, maintaining some battery level so you have always available power from both engines when you need it. Even when climbing the mountains with fully loaded car in my case, battery level never doped below 9% - of course, I had family in car and roads were snowy, so it was rather calm drive than sporty one. Maybe if I push on gas more, electric motor would drain battery even more. If you will find some closer details how AUTO mode works, let us know please.
I have the 2022 Sorento Plug in Hybrid. Love it, but one issue. I keep it in ECO and EV mode. When I leave the house with it 100% charged, why does the motor ever kick on? Since I drive only 5-10 miles a day, and I charge it to 100% each night, not sure why I am going through any gas at all???
I hear you! I am used to the Volt which runs everything on electric when it is in Normal mode (which it is always in by default until battery is used up). But with many PHEVs, and the Sorento too, there are certain conditions that make the gas engine turn on. Understanding these is what all my tests are about! What we know for certain re: the Sorento PHEV: if you turn on the heat to any temp other than “Lo” (which is just the vent) the gas engine will come on to provide heat to the cabin. If you press too hard on the accelerator (push the “tach” needle past the second hatch mark in the “Power” band on the right side tach or gauge) that will force gas engine on (and so far in my tests it turns back off soon after “backing off” the accelerator enough to get out of the Power band). Also, there are other conditions that force or keep the gas engine on (that I haven’t figured out yet). But basically, if you want to keep the Sorento in EV mode you have to 1. Keep it in EV mode, 2. not accelerate too hard, and 3. keep the heat off. If you know you are going farther than 32 miles, you might want to turn on the HEV mode as soon as you get to the highway or the fastest section of your trip. Good luck and let me know if youbhave questions!
you summarized it pretty nice. From my knowledge with Sorento PHEV so far, this are the reasons bringing gas engine on even if in EV mode: 1) anytime when there is higher demand on power, than the electric engine could provide (trying to keep the right side meter below POWER section can prevent this) 2) when you are trying to heat your interior, Sorento gets the heat from gas engine (some other PHEV's use electric heat pump instead), so turns it on to heat up. In this case, you can see EV sign still displayed green. that's because you are really powered by ev motor at this time and the gas engine is just iddling and recharging battery, rather than passing some power to your wheels - you can prevent this by not using heating. 3)I think this one wasn't mentioned - whenever there is outside temperature below 15C/59F, sorento heats up it's gas engine, just to make sure it is ready to operate in perfect condition if you suddenly floor the gas pedal and full power output would be needed as combination of electric and gas engine. Once the engine reaches desired temperature, it will again stop it and repeat all process based on the engine temperature if needed. If you are in EV mode, the heating of engine works the same way as in Nr.2 - it just recharges battery. One more point - when the gas engine is on to heat up (for whatever reason) I can see the gas consumption varies based on how much electricity I need for the electric motor. It looks like gas engine at this point doesn't only charge battery, but partially works like generator trying to supplement all electric energy to your electric motor. Finally - AUTO mode - this is mystery for me as well :-) I thought it could somehow work with maps, when you set destination in your car nav. However, I come to my destination (about 120 miles) like with 79% of battery which was definitely not the most economic route and so this hypothesis is proven as a false one :-)
Thank you Jan! And I suspected there was a temperature where the Sorento PHEV might force the gas engine on, but I figured it would be higher than 59F... I will have to test when I get home (it is below freezing most of the time this week so I should get a chance, soon). I didn’t notice the engine coming on when the temperatures were in the mid 40’s F, but that might have been due to the way I was testing it (with earlier drives in HEV mode). I sure wish Kia would just explain the conditions where the gas engine will turn on in the manual. Oh well, I guess it is also fun to try and figure it out through testing, too. :) Thanks again!!
You are right Justin, the temperature of forced engine start is somewhere below the one I believed could be a trigger point. Didn't find the break-point yet (if there is any?), so far had a chance only to test about 39F (some unusually warm winter here this year), all the trick was to keep air conditioning system completely off and I was able to drive in pure EV. Actually, I'm pretty happy to know this, now I'm able to do short city commutes in pure EV with 0 gas consumption. As for short distances I'm wearing my jacket on, heated seats and steering wheel does the comfort for me without heating through combustion engine. I noticed that with air system completely OFF, there is still some fresh air coming into car, so I didn't have any issues with humidity inside cabin or lack of oxygen. I would say this is good news helping us to stay more efficient during the winter as well. For sure - on longer journey comfort could be preferred and simple turning the air control system on, will start the engine when needed.
I am doing the same Jan! And it is good news for us because it means we can drive on electricity more often in our Sorento PHEVs. I was planning to take longer road trip tomorrow and write about how far the Sorento PHEV can go on a full charge + a full tank of fuel, but the recent weather around Seattle has turned out to be a problem. There is flooding that has closed part of our route. In fact Seattle is more or less cut off, by road, in all directions except from the north (Canadians can rescue us!). I might have to write about something else... maybe I’ll write about this problem in the context of climate change as a reminder about how important it is for us to all do what we can to address the problem (by driving more efficient vehicles, as a start). Hmmm....
Jan, as an update I have been able to test my Sorento PHEV temperatures below freezing (as cold as 30F) and was able to drive in EV mode without the gas engine turning on. I intend to test further because I do expect there is a temperature where it forces the gas engine to come on. Now, my vehicle is stored inside a garage, and it may be 10 degrees warmer inside the garage than outside, so it is possible the battery was still well above freezing temps, but I would think that the Sorento “decides” when to turn on the engine based on exterior temperature as measure by its thermometer, not the battery pack temperature (but maybe that isn’t true).
Hi Justin, I was able to reproduce EV only ride in freezing conditions as well. My car was parked outside, so at the starting point all components were on outside temperature (29F) and all went well.
This is good to hear! I haven’t yet figured out hwo cold it has to be to force the Sorento PHEV to turn its engine on… I wonder if it is in the teens…
All these experiments / tests you're doing are fascinating and interesting. I've got a new KIA Sorento PHEV Trim 4 (UK Model - equivalent of SX-Prestige) about a week ago and still figuring out the best mileage options for motorway driving. Your tests and results are extremely useful, so, thank you! A quick question: Between your first loop / test and your second loop / test, I can see that the mpg for that loop increased considerably (from 48.4 mpg to 151 mpg) which is excellent. Why did the overall trip mpg reduce from 245 mpg to 235 mpg? Just curious.
Suresh, That’s a great question! I believe the answer to why the overall mpg was reduced after the second test was because the second test also used some petrol. Of course, petrol/gasoline will always result in lower mpg than using only electricity. The second trip used less petrol, but still used some, so the overall, cumulative mpg still got “worse” after the second test. If I had made the entire second test trip on electricity, it should have increased the mpg, slightly. This has been my experience and observation so far anyway. Cheers!