Is there a legitimate use for charge mode in the Prime?

I'll ask again... What are the GPS co-ordinates of that stretch of hill where the car continues to pick up speed forever without any braking" ? Again, I remind Paul G that the car in question is a 2024 Prius Prime, not some other car. It's being driven in the normal D mode. And the phrase used by Paul G was "pick up speed" forever.

 

There are grades where you will pick up speed forever, even with all the engine braking the car can do—depending on your speed at the start.

For any downgrade, there will be a speed where your energy gain from gravity just equals what the engine can twirl off (somewhere around 13 kW in a gen 3, anyway), and engine braking can just manage to hold that speed steady. Start off below that speed, and there's plenty of engine braking to hold it or slow you. Right at that speed, holding steady is possible, and above it, you'll be picking up speed.

On a tame grade, not much to think about because whatever speed you're likely to drive will be below that critical speed.

On a very steep grade, you may have to choose a speed a lot slower than you'd like to drive, if you want the engine braking to be able to maintain it.

 

Maybe it never happened because someone was actually paying attention while driving. It happens. They likely applied the friction brakes, or is they were smarter, they engaged the engine brake. No one wants to overspeed down a hill.
It is there for a reason.

 

The first time I saw the Energy Monitor graph after going down a steep drop starting at different speeds I called it dynamic regen. That was a long time before I understood anything about how Prius decides which way and how much to use its breaking and / or regen. A lot of owners most likely ever notice those differences.

One difference I think most all of us could agree on regarding B mode is that it doesn't ever use friction brakes. At least not that I've ever noticed B using friction brakes.

 

This is quite sad. Paul Gregory (or his bot) typed 5 sentences without ever addressing the point that I made and that he quoted. I've traveled over 400,000 miles in 4 Toyota hybrid models throughout the west and have never experienced the "pick up speed" forever that he's complaining about.

One thing that I found disconcerting about the 2010 Camry hybrid's cruise control was that it would go into free-wheeling mode when cruise was set and the car was driving down hill. This is in direct contrast to the 2002 Prius cruise that would keep the speed steady even when going down a long, steep (6%) downhill stretch.

 

In my experience, gen 1's behavior was different. I drove a 2001, but I've never heard '02 or '03 were different.

In my 2001, cruise control worked just the way it used to work in conventional cars, where it was only a servo that pulled on the throttle cable. It could give you more go as needed when heading uphill, but didn't have any way to give you less go when heading down. Of course it wasn't a servo pulling on anything, just some logic in the HV ECU, but it was as if they had just copied the cruise control logic from their other cars and pasted it into the new ECU.

So in my gen 1, I did combine cruise with B mode, so it would do a better job of holding my speed on the downhills. In D mode in gen 1, it would tend to pick up speed.

So when I replaced my gen 1 with gen 3, when I first discovered the gen 3 cancels cruise if shifted to B so you can't use them together, my reaction was unprintable.

But as soon as I had observed the gen 3 cruise control using engine braking on its own in D mode to keep my speed on downhills, I stopped cussing and realized they'd made it more convenient. I no longer had to shift to B to get downhill speed holding with cruise, because they had just made it how the cruise control now normally behaves.

 

I believe that the general evolution of cruise control in general. Now they might apply the brakes if need be.

 

I don't know what had happened to this thread asking for a legit use of Charge mode, but I'll throw my 2c in.

The Charge mode is mainly for an emergency use of V2L in case of loss of power grid in natural disasters like an earthquake, which is a real concern in Japan. It can also be used for all the other good reasons that people have come up in this thread like having little bit of battery available for EV driving, at a camping site, etc. In all, it is an inefficient use of gas in any way you cut it, but now you know why it is in the car.

Pardon my intrusion if the above was already public knowledge. You can resume your fights over B mode now.

 

Coming back to the topic: have anyone some OBD App to ascertain how many kWhs are produced by a given amount of fuel, and charging speed, when the car is standing still in Charge Mode?

I want to make that test for two reasons:

- This condition is totally equivalent to an EREV, i'm having a discussion about it with friends.

- Not living in US or country where gas and electricity are cheap as hell (relative to EU), but in EU where the price of electricity for pay per use public chargers is 0,77$/kWh, i do suspect that could be even be cheaper using gas to generate electricity when you're not at home.

 

I guess Hybrid Assistant could be useful here. I'm assuming the car will just be parked. Get the data with and without Charge mode and see how much more Charge mode added to the fuel used.

 

I'm in contact with the 2 creators of Hybrid Assistant: one doesn't want work anymore on it for new cars, the other wants a car for few hours to cut short the development time. The latter is in France and i'm in Italy and the french users didn't answered the call... hence for the time being forget HA for Prius gen. 5...

About your comment: if the car is parked, without Charge mode the engine will not start, impossible comparison. If the car is moving, it's very tricky making the comparison, the charging power varies wildly and so the efficiency of the recharge. The static condition is a quite interesting start.
Here someone already attempted the comparison of FE with and without Charge mode in motion, but no coherent o complete data came out.

 

Don't need a charge mode for emergency power use. With an installed inverter(factory or not), the car runs off the battery. The charge gets low, it automatically turns on the engine to charge up the battery until nearly full, and then turns it off. That is how the hybrid has worked since before Toyota released a plug in. The plug in may only bring the battery to the high charge for hybrid mode on its own, but manually using charge mode isn't going to result in less gas burned compared to just letting the car handle things on its own.

Furthermore, Japan already has another V2L system in place for powering a house in emergencies that works with CHAdeMO equipped plug ins and even fuel cell cars. It is a 'power station' that is a home charger that allows the electricity to flow to the house. I think it came out during the first LEAF, and was available for the PiP.

Charge mode is one of those things users think they need and demand, but is really of limited use; like EV mode on a no plug hybrid. When coming to a destination without a charger, and knowing the next trip could be done within EV range, it might be worth burning the gas in Charge mode vs on a warm up cycle, and the drawbacks on the engine from a short trip. Though with that thinking ahead, you could just put the car in hybrid mode to save EV range instead.

 

Oy boy, you think you don't need a charge mode just because the engine will automatically turn on to recharge as needed? The charge mode gives you the power to choose when and where to charge the traction battery by how much, isn't it wonderful? Think of it this way, in a hot summer night in Japan after an earthquake and the power grid is toast, you need the V2L from your Prius to run your A/C unit in a makeshift camp. Wouldn't you rather have the car on the Charge Mode to charge up the battery during the day at your convenience so that you won't have to put up with the engine turning on and off intermittently during the night to jostle you out of sleep?

 

Back to the original purpose of this thread (Not the use of the "B" mode), but a legitimate reason for using the CHG mode.

If there's room to charge, it's like a pseudo-maintenance mode. When you can't remember the chicken dance to put the car in maintenance mode, and you've got room to charge the HV battery, and you want the ICE engine to run - to circulate engine coolant, or oil, or something like that.

 

It doesn't seem like rocket science to me. Jump-starting is one of the simplest of operations. We jump-started something nearly every day when I was growing up on a farm. It doesn't take much concentration to remember to hook "-" to "-" and "+" to "+." Besides, hooking it up wrong is something you won't repeat, because it can result in a shower of sparks.