2020 Prime / Charge Mode

Discussion in 'Prime Main Forum (2017-Current)' started by JJWax, Feb 10, 2020.

  1. JJWax

    JJWax Junior Member

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    Hi all, can you give me a primer on why it isn't (or perhaps is) a good idea to constantly use Charge Mode to charge up the electric battery with the gas engine, then use EV Mode until it depletes, then charge up again using Charge Mode? I missed that day in HS science class that would have explained why this isn't a quasi- perpetual energy machine. :)

    The only other pause I have is that my new Prius Prime seems to have a burning rubber smell when I use Charge Mode.
     
  2. Rob43

    Rob43 Senior Member

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    In almost every scenario (I personally know of none), it's simply not as efficient.



    Rob43
     
  3. john1701a

    john1701a Prius Guru

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    On vacation when there's no where to plug in, having electricity available for short trips is overall more efficient than a warm-up cycle. It's easier on the emission system too.

    It's a nice perk to be able to warm/cool the cabin with electricity remotely then too.
     
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  4. Sarge

    Sarge Active Member

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    I think the short answer here is any time there is energy conversion (I.e gas to electricity) there is energy loss involved, so if you compare the gas required to drive a set distance in hybrid mode vs running charge mode for a period of time then EV to run out the charge for the same distance, it will likely take a bit more energy using Charge due to the conversion losses. In theory anyway. Unfortunately, there is no free lunch.

    As mentioned above, it seems the Prime use case (pun fully intended) for Charge mode is to rebuild some charge when you know you will be in a situation where it will be needed (stop & go traffic), or upcoming short trip following your next destination when you know you won’t be able to charge and avoid an inefficient warm up when stopped or barely moving, etc.

    IMO, anytime you know you will charge at your destination you should run the battery down completely, but if you know you will not have a chance to charge, running a bit of charge mode to build up a bit of range so you can pre-condition the cabin or at least get to a cruising range section of your next trip (for warm up while rolling) may be optimal. But not a big deal if you don’t think of it, Prime is still a super-efficient vehicle regardless. ;)
     
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  5. XCAPE LA

    XCAPE LA New Member

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    I also had the burning rubber smell after using charge mode in the first couple of days. I haven’t had that happen since (but I do rarely use the charge mode).
     
  6. 3PriusMike

    3PriusMike Prius owner since 2000, Tesla M3 2018

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    I don't think there is anything that is a quasi-perpetual energy machine. Energy conversions are either following the laws of thermodynamics or they aren't (and are impossible).

    Using charge mode takes X amount of energy from gasoline and loses about 60% to heat and takes the renaming 40% and converts some of it to electrical energy (maybe 80-90% if not moving). Later, when you chose to, you take that electrical energy from the battery (maybe 90% efficient) and you convert that to the motor to turn the wheels (maybe 90%). All numbers are examples.

    Since you end up with far less than X amount of energy turning the wheels you can rest easy that no laws are being broken and the thermodynamic police won't be making an arrest.

    Depending on how you drive, the distances involved, ICE warm up cycles, the weather, use of HVAC etc it might be more efficient to use charge mode or might be more efficient to just use gas. Both involve lots of energy losses.

    Mike
     
  7. JJWax

    JJWax Junior Member

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    Thanks all for the thermodynamics lessons! The basic question for me is what lengths I’m ultimately willing to go to have semi-regular EV mode driving, given that I park on the street (so no plug at home) and my company is delayed in getting their promised charging stations set up at my parking garage at work, so I’m not able to charge regularly.

    For me it’s not just a question of pure efficiency, i.e. I’m willing to expend a little more gas in order to get semi-regular 20 mile intervals of pure EV driving. I find the Prime to be a wholly different car (and much better driving experience) in EV mode vs. any other.
     
  8. Rob43

    Rob43 Senior Member

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    Ask your company to install a simple 240 volt outlet (NEMA 14-50R or 6-50R) within the next month, then use your Toyota OE EVSE unit with an adapter for 240v charging.

    This will cost them very little and cost you virtually nothing, but your charging rewards will be incredible.


    Rob43
     
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  9. FuelMiser

    FuelMiser Senior Member

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    Sounds to me like you've made up your mind. Perhaps you were trying to find if using Charge Mode would "hurt" the car in some way and thus should not be used on a regular basis, but it seems the only penalty is the extra gas use. I have never driven a Prime, but I've seen several comments on how different the Prime is in EV vs HV modes, especially when switching from EV into HV mode with a "cold" engine. I can't imagine the HV experience in a Prime could be so much different from the HV experience (the only experience) in a Hatchback. So, that must mean that the EV experience is quite spectacular in the Prime!
     
  10. NSXT

    NSXT Member

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    It is amazing! Book a time with a Toyota dealership and find out (EV + Power Mode + full throttle = Blast off) :D
     
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  11. jerrymildred

    jerrymildred Senior Member

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    That might be a bit of an exaggeration, but it is very nice. However, imho, not nice enough to warrant spending extra gas to enjoy it. Around town, my Prime spends about half it's time with the engine off even in HV mode. In a sense, it uses one or two mile long bursts of charge mode all by itself when driving under about 60 mph.
     
  12. drash

    drash Senior Member

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    It’s no different from the regular Hybrid mode where the engine constantly cycles between recharging what it used when being helped by the battery. It’s just on a bigger scale. The only bad things about the Charge Mode is it doesn’t allow the engine to shut off or use assist from the battery like normal Hybrid Mode and it’s a very manual process. If you are on a highway, no big deal. Mathematically it’s probably very similar to just using Hybrid Mode all the time because the Prime is a beast in efficiency but more fun because in EV Mode you get to use both motors. I guess it puts a new meaning to “self-charging” hybrid.


    Unsupervised!
     
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  13. PT Guy

    PT Guy Active Member

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    "my company is delayed in getting their promised charging stations set up at my parking garage at work,"
    Is there a standard 120 volt receptacle in that parking garage that they'll allow you to charge at? 5 hours for a full charge @ 120 volts, so you'll get the full charge in less than a work day.
     
  14. jfschultz

    jfschultz Active Member

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    Back in November I was working on using up the nice full tank of E10 the dealer "gave" me. Charge mode helped and got me an "amazing" 25 MPG!
     
  15. Trollbait

    Trollbait It's a D&D thing

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    Maybe if you had stretches of highway driving that were long enough to charge the battery, and then switched to slower streets the range of the EV mode.

    If your commute has a stint of higher speed cruising, you could get enough charge for the next start up to reduce the warm up penalty.
     
  16. jerrymildred

    jerrymildred Senior Member

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    I tried that on the interstate on our vacation last May. Mostly 70-72 mph. It did not improve average mpg compared to just plain hybrid mode. It looked like it was actually slightly worse, but not much.

    Due to thermal losses, you're better off, on a trip, just leaving some charge in it for your destination rather than using it all up a highway speed and then recharging it with gas. I got much better overall results that way.
     
  17. smyles

    smyles Active Member

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    Someone on youtube did the real life test, and as expected the charging mode was the least efficient (iirc - it's been awhile).
     
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  18. Toyo_Tom

    Toyo_Tom New Member

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    If you run just in "normal" HV mode, the car will still do limited charging when it is able to (normally when cruising on highway without significant uphill slope). You can monitor this on your screen if you want, and see where your power is coming from and where it is going. If you are not able to plug in regularly, I recommend switching to HV mode immediately when you enter highway driving and back to EV mode when you are in low speed or stop-and-go driving. As long as you get a fair amount of highway cruising as part of your driving, the car should be able to maintain your battery level fairly well under these circumstances. Generally, I would avoid HV charging mode unless you are depleting the battery significantly and need charge for a long stretch of stop-and-go driving. Aside from the conversion loss mentioned before, the engine (by design) isn't really up to the task of handling all the power-providing duties except during times of limited acceleration and probably won't give you very satisfying response.
     
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  19. yaun

    yaun Member

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    My understanding is that the only time it makes sense to use charge mode is if you are planning to use the battery for something other than driving and have no way to charge it up. An example would be if you are on a road trip and want to car camp and need a full battery to run your AC for the night.

    Since the efficiency of the engine is lower at low RPM and not entirely linear, there may be theoretical edge cases where this outweighs the energy conversion losses of charge mode, and thus you could gain MPG by using charge mode at highway RPMs and then use the energy at low RPMs. But it's doubtful that it's possible to make efficient use of this in the real world. If there would be an easy rule to follow, Toyota would have already included it into the hybrid system logic to get even better MPGs.
     
  20. Old Bear

    Old Bear Senior Member

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    While you might use this strategy solely for the pleasure of driving in electric mode, it is inherently inefficient because you're burning gasoline to run an engine to drive a generator to charge a battery to run a motor to power your car. At each step of that multiple conversion process, inefficiencies are introduced and some of the energy contained in the gasoline is lost as heat. As Scotty used to say on Star Trek, "You cannot change the laws of physics."

    So, other than for the fun of it, why have charge mode at all?

    The answer to that questions lies in public policy being adopted by many cities and communities around the world to limit access to zero-emission vehicles during certain periods or entirely.

    See this article: Cities eye zero-emission futures - CSMonitor.com

    So, let's say you have to drive 30 miles from home into a zero-emission central city downtown where you can park in a garage and re-charge your car for your return home. Your Prime will have little problem driving 25 miles in electric mode, but it will then cut over to gasoline just as you are entering the city center. The local traffic warden then proceeds to issue you a hefty fine for violating local air quality regulations.

    However, if you drive your Prime in charge mode so that you have a sufficiently charged battery as you enter the city center, you can then operate as a true zero-emission vehicle to get to your garage -- or even to drive around the city in electric mode until you depart from the zero-emission zone and change to HV mode on your way home.

    In other words, there may be occasions when you have to run in EV mode and the ability to keep your traction battery near full charge will be important.

    Confession: I've been known to run in charge mode on the way to visit friends who live 35 miles away so that I could let them have the fun experience of getting to drive my Prime in EV mode. After all, what good is having a very cool toy if you can't show it off to your friends? :)
     
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