Prius Prime: detail about Charge-Mode

I don't think you're missing anything. People are just looking for a use for Charge Mode on the Prime. Just because it's there doesn't mean it's useful much of the time.

 

My only experience with a regular Gen 4 is with a trim 2 with NiMH battery. Li-ion might be different. My wife's 2017 trim 2 kind of tries to do what the Prime does. But it's not NEARLY as eager to jump into EV as the Prime, it doesn't go anything like as far in EV when it does that, and it jumps back out of EV with very little push on the accelerator. The models with Li-ion batteries might be more robust in this regard; perhaps someone with that battery in a regular Prius can tell us. But even they don't have the battery capacity to mimic the Prime's behavior at low to medium speed in HV mode.

 

When not in Charge Mode, and especially after Charge Mode kicks off due to hitting 80%, driving the car in HV mode at the mid-eco throttle line (at what speed doesn't seem to matter much if at all) tends to add another 0.3 miles or so of EV range within a minute or two. Then it stops and HV mode maintains approximately that as the top end of its target range, very rarely going above it except via regen. Once up the 0.3 miles above where Charge Mode stopped, you can click twice to go to EV and back to HV. Then it will set about adding another 0.3 if you again put the throttle to where it most enjoys charging. So, you can slowly pump it back up to 100% if you have a real need to, though I'd discourage routinely doing so. It's a lot of work, and it probably doesn't charge you up any faster than something like an L1 or L2 charger, exactly as Toyota intended to limit you to doing.

You can even pump it beyond 100% that way on level ground, it just won't display it. But you can figure it out by just continuing your pattern to add another 0.3 miles another 2 or 3 times. You can confirm this by driving in EV mode and going the expected distance before the EV range starts dropping. Not a trick to be used routinely, but a good one to know if you're not going to be charging, and want another way to slowly get to 100% without plugging in, when approaching some big need for driving in EV.

 

an fyi for those interesed in verifing for themselves.
I just did 9 miles using CHG mode at 65 mph and got 10% added to EV from ---- on the MID. I'd done a 50 mile trip a month or two ago and it took all 50 miles at 75 mph to go from really low, 1 or 2% to 80% so I wasn't surprised at the 10% I got for 9 miles at 65 mph.

I took back roads on my way back at 50, 45, 40, 35 and 30 mph for 12 miles and filled the rest of the way to 80%.
ambient temp was 45 F and raining lightly. I also used heat directed at foot and windshield at 72 F which still gave me 4 square on the MID's HVAC score.

Since my 12 v is getting questionable at most every stop I'd shut off wipers, HVAC and go back inot EV mode to shut the ICE down and use a bit of EV to get going again.
Final MPG for the 12 miles was 30.3 but I had a long steep uphill where I should have turned off CHG mode for that climb, if I was thinking ahead at the time.

ie edit: last few times I've used charge mode from Low or no EV miles available it's taken about 1/2 hour to get to 80% no matter what speed the car is going.

 

The HVAC score might as well be a random number generator. It doesn't even change if the AC is on or not in the summer.

As long as the car is in Ready mode, the DC-DC converter should power all the 12V accessories from the traction battery. It doesn't matter if the ICE is on or not, nor what speed you're going. Even if you have no EV range it works as part of HV mode.

It seems to charge at 12 kW, so that's about right. It sounds like it's taking a little longer on the highway. I haven't tested it, but maybe it slows down the charging if the engine load is already high.

 

I like this writeup because it gives more clues to how the car works. Seems you've noticed - in the scenario above and possibly / probably other scenarios - when the Prime likes to regen / recharge most often.
Just another variable to keep in mind when trying to understand Primes big picture. Tanks OptimalPrime ie: OP OptPri OpP OlPe ??

 

I recently did a Charge Mode test while idling. While sitting stationary in Park, in EV mode, I let the EV Range drop from a few tenths of a mile I had left over from a trip, to 0 EV range and showing just dashes. Then I put it into Charge Mode and sat there while it slowly added back EV range. I did not touch the gas pedal. 88 minutes later, it switched itself out of Charge Mode upon hitting 80%.

So, Charge Mode charges at about 3.5kW while idling in Park, if 0-100% is considered to be a 6.6kWh charge.

I'll review my video of that experiment to determine the exact gas consumption, which can be easily calculated because I didn't reset the trip mpg meter after taking a trip that burned under a gallon. I think the answer is around 0.7 gallons, but will update this thread with the exact answer when I get around to reviewing the video and perhaps posting a sped-up version on YouTube for posterity. I probably ought to do 88 minutes of forced idling in HV Mode with 0 EV range (or better yet some constant range such as 2.0 miles, for better accuracy in case HV decides to charge/discharge), under identical weather conditions, to know how much gas went to idling the ICE, and how much incremental gas was used to do the charging. Surely the idling overhead is a killer compared to engaging Charge Mode while driving, where the idling overhead is already "prepaid". Not to mention that it lasts for only 1/3 as long, if the half hour number is accurate.

 

88 minutes seems like a long time to let the engine idle.

 

It was a long time to sit there taking video of the EV range going up by 1/10 of a mile every 20 seconds or so, that's for sure. Like watching the grass grow. But as far as worrying about idling hurting the car, I have no concerns about that. As long as the radiator fan doesn't die, I'd have no problem with idling any Prius in perfect shape, for any amount of time.

Admittedly, what I was doing was more strain on the car than just idling, as it was pumping about 3.5kW into the battery the whole time. That's about 5hp worth of electricity, probably taking 6hp of engine output above what just idling with no load uses. I think it was burning just under 0.5 gallons per hour. I'm guessing that would normally propel the car 40mph on level ground, getting 80mpg. So idling in charge mode, stresses the car the same as driving 40mph on level ground without getting the benefit of 40mph air coming in through the grille. Probably not as bad as sitting idling in a conventional car with the AC drawing a good load on the engine.

I should do it again and monitor oil temp, coolant temp, ICE rpm variations, etc.

I know of a woman who left her Gen 4 Prius in Ready mode for several months, 24/7. She was running the climate control for her pit bull while on a "Prius Camping" road trip. I hope she turned it off when refueling, and to check the oil, but she sort of implied that she had not. She'd leave it running all day, even while out walking with the dog, while the dog was in the car and she was grocery shopping, while sleeping in the car, etc.

 

That is kind of inline with what I can see when I'm charging at a L2 station. If the EV range has just reported -- then I will need 2:00 hours to fully recharge ( according to my car ). In reality , it will recharge around 98 min at 3.5kWh and then during the last 20 min or so it will slow down to get a full charge. In total around 6kw ( more or less depending on the temperature ).

 

Great info. Thanks!

Though I've charged using L2 hundreds of times, I never paid much attention to anything but how long it took to finish.
That was usually right around how long it said it would take.

 

Very interesting and encouraging information, considering that I want to use my Prius Prime as a power source during emergency power outages. The 120W “cigarette lighter” taps are OK for recharging cell phones and computers. But for larger power needs, I want to tap the traction battery reserve. I plan to access that via a 1500W inverter attached to the 12V battery. I knew I could recharge the traction battery using my generator; but based on your information, I now know it can also be recharged using the ICE. Much nicer! Thanks.

 

The first few times I looked at the graph, I didn't really notice the charge slope at the end. Not sure what that was about with me.
I did notice the first time looking at the graph the 2 times the charge shut off and the 5 other times it slowed substantially.
Very nice detail while charging. thanks

 

Regular Gen 4 does it too, but the Prime is more eager to go to EV ... at least compared to my wife's Trim 2 with the NiMH battery. The Lithium based Gen 4 might be different more like the Prime but I don't know.

 

It took a bit for this question to bubble to the top of my brain. Having experience with both the Prime and the 4 Touring, do you have a comparison about how eager each is to shut off the ICE when at slow to moderate speed?

 

I've noticed that. It makes it way easier to get extra miles per gallon. (or km per liter as the case may be )

 

I use it for a modified pulse and glide technique to squeeze extra mileage. I build up speed slowly with the ICE and then let off the gas far enough to go back to EV mode. Then I push the gas right up to the line where it will usually switch back to HV. Even on moderately uphill sections it greatly increases the "glide" time between HV pulses.