HV mode usage of EV battery portion

2) coming downhill will continue to fill the battery, but it won't reserve it for ev mode. if you keep driving hv, it will eventually use it.

1) something near the sliver, but idk exactly

 

The answer is yes and no, depending on who you ask. There are some reports that HV mode in PRIME utilizes the bigger buffer of the traction battery than regular Gen4 Prius and results in better mpg under strictly HV mode. I myself did experiment and did not find that to be the case. Whether I have a full traction battery or 50% or --% (i.e. 0%) SoC, for my driving condition, it did not make any difference in mpg or use of traction battery SoC under strictly HV mode. I reported my result in other thread, but I don't have a quick link. If and when I find it, I will post it here.

Answer to this question is unequivocally it will continues to charge the battery until the full capacity. I just did that experiment as well. Provided you have a long enough hill or a long enough drive to regen energy, depleted EV range "--" SoC can be replenished all the way to full WITHOUT using CHG mode.
Read this thread: Battery Charging After Depletion? | Page 2 | PriusChat

 

I think if the SoC is replenished by a long hill regen, it can be reserved for future EV mode use. I may have to toggle the HV/EV switch to lock in the SoC at the time it is fully replenished. But I don't think regen replenished SoC is any different from CHG mode replenished SoC or for that matter wall charge replenished SoC. I know as a fact that under strictly HV mode, the car does keep the SoC very much steady with a minimal loss. For example, when I am heading to a city on a long trip, I usually try to keep the SoC for the destination. Starting with 100% SoC on the dash, driving strictly in HV mode for 300+ miles, I can finish the HV mode portion of the trip with 95% or more SoC left before switching to the EV mode in the city.

 

i know it will keep a wall charge, and charge mode charge. i haven't read of anyone refilling on a long downhill and experimenting with hv and ev. you could be right, the pip won't keep it unless you regen in ev mode.

 

It's not a long hill, and it's not a full charge, and not all the regen are strictly under HV mode, but "trickle" charged SoC using regen only from depleted EV range on my PRIME two days ago is still at 14%. I can keep this SoC for EV mode drive next week for sure.
Battery Charging After Depletion? | Page 2 | PriusChat

 

That was what I thought. But on my recent experiment, EV to HV after EV range depletion and on HV regen to replenish EV range SoC, after 3% SoC appeared on the dash, it did not default back to EV mode. It stayed HV mode until I manually switched to EV mode. @CharlesH reported this phenomenon.

I will have to try again with a long down hill next week.

 

Sure you have. You just forgot. Well, I'm pretty sure you did. I charged mine to 98% coming down a mountain in Colorado. Both the PiP and the Prime will lock in the charge level when you regen in either mode and then toggle the EV/HV ending up in HV. In other words, if you're in HV going down a big mountain, both cars will regen all the way down or until the battery is full or overheated. When you level out, put it in EV and then back to HV. That'll be the new level of charge it will maintain. If you're in EV coming down, just put it in HV and it'll hold that SOC. I did it in the Smokies with the PiP and the Rockies with the Prime. I've also done it a little at a time on flat roads using the same technique after braking for stop lights just as an experiment.

 

Yes, that is what @jerrymildred is saying and I think he is correct on this as I stated in my comment above him. I will test if the toggling is necessary to keep the SoC or not. I will regen "--%" in EV SoC in HV mode next week on a hill near me that will give back ~30% of SoC on it's descent.

 

we don't have any hills around here, so i must not have paid attention to that one

 

You are correct. Regenerating in HV going down a mountain that puts 10 miles back in your battery is treated by the car exactly the same as regenerating a half mile of charge stopping at a traffic light on a 50 mph highway. If you don't lock it in by putting the car into HV (EV and then HV is you were already in HV -- it HAS to go INTO HV to set the new level), then the car will use that excess charge to improve gas mileage while returning the battery to its previous level.

 

A short trip like that is not very good indicator of the true mpg, but one explanation is that even if you switched to HV mode immediately after you started the car, the car probably used the traction battery to propel the car during warm-up cycle. During the warm-up, the engine is on, but most of energy used for propelling the car comes from the traction battery. Did you check your traction battery SoC after the 7 mile trip? I bet it wasn't at the 53%.

 

It is possible that PRIME uses some stored EV portion of SoC on initial warm-up and beyond. That may contribute to the reported better than regular Gen4 Prius mpg in HV mode. I myself have not seen any of my HV only drive to show extremely high mpg over the longer drive (~40miles). In any case, mpg displayed on PRIME for such a short trip is very inaccurate for sure. For longer trips of more than 30miles, the dash mpg is usually close to what I see on the Hybrid Assistance App from via OBDII reading.

 

It's been my observation that it does eat into the SOC quite a bit during warmup. If your trip is done before it pays all that back, you can get some pretty astonishing MPG numbers. Once it's warmed up, when driving at 50 mph or so, it'll still put itself in EV and take from the EV range for about 2-3% SOC and then pay it back by running the ICE. The more cycles of that it goes through, the less effect on trip mpg it'll have. So it's negligible on a 150-mile trip but significant on a 10-mile trip.