Can using CHG Mode be more efficient?

Now that you mention it, I seem to recall reading something like that a week or two ago.
Sorry, it just sounded to me, the way I read it, that the proof was from one experiment, and not 2 or several. And not too many nasty variables involved while sitting in P stationary and in CHG mode.
I'm sure you're aware how much emphasis I attribute to those variables.

Anyways, I've made a few more CHG mode runs of 130 miles round trip. I tried and failed to get 2 CHG mode cycles in one trip by about 20% SOC at the end of the trip. I had 60% SOC at the end of the 65 miles. I'd run CHG mode from the beginning of the return trip, than EV mode using all available EV range, than switched back into CHG mode for the remainder of the return trip. I haven't pulled the data yet, so I'll post when I review it more closely.

 

It's possible that CHG mode might get more efficient as more history data gets compiled. We'll have to see what happens as CHG mode gets used by others more often than once or twice a year, like I've done in the past. Probably not so much idling though, especially if that kind of test is done more frequently. Like if camping in the Prime. Warm up cycle, up steep enough hills also trashes efficiency in CHG mode, even more so than in pure HV or HV + EV range per trip / session.

edit: before I forget, there is also the issue of how clean the regeneration is. (refering the toyota recommending a steady pace for best efficiency. It's easy enough to see how charge mode varies it's charge level on hilly terrain when using DrPrius. Using CHG mode on rolling hills can increase what DrPrius shows for pack module internal resistance. Than using Level One plugin charging can reduce the internal resistance per module. As it's a much steadier slower (cleaner) charge.

 

I think we're hobbled by what appears to be the car's charging limit of 3.3kW. It seems as though the electricity generated in CHG mode is fed through the same system, so we can't generate more.

I can say with dead certainty, however, that regenerative braking is not subject to that limit. Interesting.

 

I've played some more on the same trip as I've had a few days where weather allows no HVAC use at all..... On my trip CHG mode costs 12MPG. Thats at roughly 77-80MPH (per Prius, though Waze/GPS says thats 75-77MPH). I can still get better overall MPG by 1-4MPG (overall trip of 66 miles) by running CHG mode to get some miles back before arrival at my destination, then kicking back to EV mode and arriving with little or no EV charge left. I'll keep playing, but probably not able to get as scientific as ya'll. I do have paid for torque app and a bluetooth adapter if someone could tell me what values to data log I'm happy to do so. Won't stop this commute any time soon, however it's getting COLD here so heater use is going to start to be a thing....

 

Aren't CHG mode and Regenerative Braking both supplying charge to the Traction Pack by using either or both MG1 and MG2?
https://en.wikipedia.org/wiki/Hybrid_Synergy_Drive
scrool down 3 or so page screens for this item.

MG1 and MG2

MG1 (Primary motor-generator): A motor to start the ICE and a generator to generate electrical power for MG2 and to recharge the high voltage traction battery, and, through a DC-to-DC converter, to recharge the 12 volt auxiliary battery. By regulating the amount of electrical power generated (by varying MG1's mechanical torque and speed), MG1 effectively controls the transaxle's continuously variable transmission.

MG2 (Secondary motor-generator): Drives the wheels and regenerates power for the HV battery energy storage while braking the vehicle. MG2 drives the wheels with electrical power generated by the engine-driven MG1 and/or the HVB. During regenerative braking, MG2 acts as a generator, converting kinetic energy into electrical energy, storing this electrical energy in the battery.

I don't know about any of you all, but to me that is about as clear as mud when trying to understand what's actually going on when the Prime is in CHG mode.

 

As far as I know. I can tell you that it's easy to generate 60+% SOC in 20 minutes going down a steep grade. That's a charge rate of ~11kW.

As with all things, the Prius design is a set of trade-offs. I suspect that the decision was made the CHG mode, being under the control of Toyota's engineers, would not exceed the 3.3kW charge rate for battery preservation. Regen is a different beast. If the car is to have regen at all, the amount of power generated will vary depending on a number of factors outside of Toyota's control. They can bleed some excess power off by spinning the ICE, but only so much. I think there's a saturation point and there's nowhere else for the excess power to go but into the battery.

 

I don't understand. CHG mode only ever gets 3.3kW charge rate? And going down a steep decline in EV mode can produce 11kW regenerative charge rate? Why can't CHG mode also produce 11kW's up to the 80% SOC cutoff mark, when EV mode regeneration can produce 11kW regen up to %100 SOC?
Do my questions make sense?

 

Toyota probably doesn't want the increased battery degradation that comes with the higher charge rate. For regen I don't think there's a lot they can do to avoid it.

 

My thought is CHG mode may be throttled under certain conditions, where as regen under EV might not be. Going down long hills might be one instance when regen is EV mode might be more efficient / produce more kW out than CHG mode under the same conditions.
Whatever is actually happening, half the time it's really difficult to pin down exactly what it's up to.​

 

I still have a hunch CHG mode is just a fixed amount of throttle added to the engine - warm-up mode that just runs until SOC is 80%. Everything else would operate normally. Next time I drive up a steep hill with gas I will try CHG mode to see if the higher RPM causes faster charging.

 

I hate having to go up steep hills I'll even take a longer trip if I can find a route that is less steep than another. it's one of my hypermiling OCD issues, I guess. I don't follow the hows and whys, but that doesn't make your ideas any less valid than mine or anyone elses. Specially since we have at very least, different temperature range and topography.

 

Interesting! I don’t have the numbers in front of me, but I posed them here several years ago. IIRC, my test was more in the 75MPH range, and charge mode did not come out on top, so to speak. It sounds like, at lower speeds, it might be a different story.

I concluded that the only two cases where charge mode really makes sense are:
— I would get home from a road trip with too much gas in the tank (point being that my day-to-day driving around town is almost entirely EV, road trips are rare, and if I leave too much gas in the tank, it’ll get pretty stale.
— I unfortunately hit a stoplight during the warm-up cycle, but for some obnoxious reason, the computer doesn’t direct the energy of the warmup to recharge.

 

I stumbled upon another use for CHG mode a week ago.
I had no EV range left, so I couldn't switch modes into EV, obviously.
I was at the top of a 50' foot in 1/4 mile hill at about 40 mph.
Just over the top of the hill I held the EV/HV button for 5 seconds to switch into CHG mode.
and coasted down the hill which was steep enough to hold the 40 mph speed all the way down the hill.
There was a Red Light at the bottom of the hill I had to stop for. While waiting for the green light, I went to switch off CHG mode and found I had enough EV range (about 5/10 of a mile), so I was able to switch back into EV mode. A couple more hills and switching from EV to HV to EV again and I was back with a decent about of EV in reserve.
Same can probably be done just switching from HV to EV etc. But CHG mode on a steep enough, long enough hill, makes short work of building up EV range when there was none to work with before switching it on. As always, YMMV

 

I found charge mode to be beneficial to my side-gig. As I am delivering orders and flying around town, my EV mode enables quick maneuvering and acceleration from stoplights. But it doesn't last that long before depletion. When I accept an order that requires some distance, I kick it into Charge Mode and it's surprising how quickly it recovers to 80%, and I'm good to go around town again.

 

I verified that charge mode is indeed faster under driving conditions. It seemed to go as high as a 7 kW charge rate. However, even though I ran charge mode and depleted the EV for the rest of the trip, my overall mileage was worse than driving that stretch in pure HV mode.