Hybrid Mode

so after 22 posts, no one knows the answer to o/p's question?

i can only comment on pip, hv mode preserves most of the wall charge, but not all.

 

Well I guess there's an easy way to find out. If there is EV range available switch into HV mode and watch the energy monitor for flow to and from the battery. If the system considers it all one big basket of available charge then as long as you have EV range you should only see power flowing from the battery, and only see power flowing to the battery during regen. Once HV mode has used up all of the EV range then not much later you would start to see charging coming from ICE as it will then be keeping the battery within the minimums needed for HV mode.

Probably a little easier to see on the 11.6 inch screen whether the charging is coming from ICE or regen because the 11.6 inch diagram is a little more clear, but it does show it on the 7 inch screen also.

 

In HV mode, the system is in "state of charge preservation" mode. If you are in EV mode and push the HV button, the system will run the engine to maintain that specific state of charge at the moment you entered HV mode. If you are in EV mode and it gets down to a certain level, the system forces you into HV mode, and maintains the charge at that (minimal) level. Still HV mode, just a different set point. If you climb a long hill and drain the battery far enough, you are forced to HV mode. As you go down the hill, the state of charge will increase until EV mode is available. If you stay in HV mode until you get to the bottom of the hill, the additional charge will then be consumed until you get back to whatever the "set point" is when you last entered HV mode. Halfway down the hill, you can hit EV and then HV, and put the set point to whatever the state of charge is at that instant, and when the hill is past, that is what charge level will be maintained by the engine. I have done this many times. (Really annoys the spouse.) So the size of the "HV portion" can be whatever you want.The system just enforces a lower bound.

Concerning the idea of "HV" portion of the battery, pre-production versions of the first generation Plug-In indeed did have separate HV and EV batteries. The EV battery could only be recharged by plugging it; no regeneration for it. The HV battery was just the battery from a normal Prius. But by the time the Plug-In went to production in 2012, they had transitioned to a single traction battery, with "HV" and "EV" portions being a fiction created by the software. But descriptions of the two-battery setup linger on the Internet, and people come across them, not realizing they are describing an early prototype.

 

That's a half-truth. The car won't let the battery drain beyond a certain voltage at which severe damage might occur (which depends on battery size and chemistry), but it can be drained to the point where it will not be used, at all, to propel the car. I have done it multiple times in my 2004 climbing the Rocky Mountains. Battery drained, pedal on the floor, no power from the battery at all. This condition is sustained until the conditions allow power to flow from the engine or wheels to the battery and recharge it.

That's true, but it's generation, not motoring that's required to transmit torque from the ICE to the wheels. Therefore, no battery power is required. MG1 generates power, that power is pumped to MG2, no current flows to or from the battery.

I have not been able to drain the battery in the Prime. The control system is better and the engine is more powerful. However, it's likely possible.

 

So it would seem that "portion" or "partition" is a valid way to describe things, at least in a general way. However I can see the drawback of explaining it that way is that even if someone understands that it's just one traction battery, some people might still get the wrong impression that there are separate physical areas of the traction battery where the two different "charges" are stored. Unless they understand the concept of hard drive logical partitions which not everyone does.

So probably simple is best, summed up in one sentence which is the system preserves your current EV range when you switch to HV mode. Probably for most people that is a good enough explanation, at least when they are first learning about it. For those who want to know more I think your detailed explanation using set points is clear.

With the type of driving that you do if you haven't been able to drain the battery then I would say for most people it's not going to happen. However I suppose when the car is say ten years old and the traction battery is slightly degraded, combined with driving during the winter, that might create a few more scenarios that people could run into.

 

Simple answer: HV mode will drain down the remaining % of the traction battery depending how you control or modulate the EV operation in the HV mode; and also the amount of brake regen from the driving condition.

If you use the traditional method to induce EV operations by letting the accelerator off entirely, and then push the accelerator below the ICE threshold, this driving will slowly drain the remaining power from the traction battery.

For example, I have 60% battery left (you can change the dash to display remaining %). Then I use HV mode, but induce the EV operations on a long stretch of flat road with no lights........then the traction battery will slowly deplete 59%, 58%, etc. But if you have some long brake regen, then it will go back up 59%, 60%.