Prius Prime 2021 why EV battery stops charging once empty

Welcome to Prius chat.

The car wasn't drained as you describe, but they added a feature called "Charge Mode".

To access this mode, hold when pressing the HV/EV button for a short period of time and it'll be selected. This mode only works if the battery is below 80%.

Good luck and keep us posted.

 

There is only ONE high voltage "hybrid" battery. It is much bigger than in a conventional hybrid.

In general, the "top" xx percent of the battery is used for EV operation.
When that is gone, it switches to a mode similar to a conventional hybrid and will not try to charge the EV part of the battery capacity because it is inefficient to do that much charging with the gas engine.

 

OK, so I worded it poorly.
IN NORMAL DRIVING, the car will not make a "conscious" attempt to charge the EV portion of the battery because that is not energy efficient.
Going down a LONG downhill grade is about the only circumstance where it will.......because that IS efficient.

 

not sure what you mean by lost energy. prime will keep charging the battery if there is excess energy to be had.
and why would you want to waste gas using charge mode?

 

The car will continue to charge/discharge the battery, aiming to keep the battery level stable in HV mode. When you first deplete the EV range, that means the car will try to maintain the battery at 0% EV range.

With a long hill to descend you can “trick” the car, and fill the battery up a bit. You can get the car to maintain that level by selecting EV and then HV mode.

Another option is to use the “secret” CHG mode. But keep in mind, the car is usually most efficient when just driven.

 

Energy lost? I'm seeming to remember that some drivers have refilled the EV portion of the battery, completely or near so, on some very serious descents. Think Mt Evans and Pikes Peak.

But it does seem that there may be the appearance of a gap in the display, such that for small descents, the EV range does not rise above zero. But I don't recall any indication that potential recharge energy is actually lost. It just doesn't display as some expect.

 

No energy is lost (except when in Neutral). With sufficient continuous breaking it will go above 0%. The indicator is not precise.

I would recommend against CHG mode unless you need the EV-only operation. In my testing it is less efficient than letting the car take care of itself.

 

when you brake, the energy goes into the battery. there should be a screen showing you this. the only time you can waste energy in any prius is when the battery is at the limit set by the software. for a prime, your icon would look the same as if you had just finished a wall charge, or at least 80% of that.

i look forward to @Raytheeagle explaining to the rest of us what makes sense to you
how would charge mode keep the car from wasting energy?

 

My crystal ball is foggy these days.

My understanding of Charge mode is that if the battery is below 80%, charge mode will charge the battery.

If the battery is not showing any percentage (I.e. the battery has progressed from any EV range), it does take a bit to get back on the percentage register.

Maybe that's the perception of lost energy ?

I'm sure we'll all find out together.

 

i'm not so sure...

 

Oh! I've had it all wrong then. My bad.

 

No worries Dave, we’ve all been there

 

I have owned a pp for less than 24 hours, so please, if you are gonna beat me, please use a wiffle ball bat!

I used charge mode last night on the highway.
Charge mode will use the motor generators to put charge onto the battery.
Now it will use higher rpms which translates into using more gas fuel, i.e. less efficient than standard HV mode.
Dont know true mpg, but watching vids about it says around 40 mpg.
(might need a math wizard to calc added EV range etc to see if price point gas/elec conversion evens that out)

When in HV (if there is no EV batt left) braking and such will still charge the HV batt,
there is no energy lost.
I seem to have experienced this yesterday within the first 30 minutes of driving (since I did not charge it first)
While the EV range still shows at 0 percent, it will still allow MORE use of EV operation.
I was able to use MORE gas pedal, higher speeds etc without the engine kicking on.
Was using AC also, so remember that also uses much electrons too.

This is just my experience and first initial gatherings.
Im sure many others will be able to add more in depth

 

As already said by others, there is no separate battery for hybrid and EV. It is one large traction battery of which the last bit of charge left (below 14-11% SoC to be exact) is reserved for HV use. The gas engine or regen braking can charge the traction battery above this threshold either by forcing (CHARGE Mode) engine to generate electricity or possibly by regen although it will take a quite bit of a long downhill to capture enough energy. I once charged the "empty" traction battery all the way to 100% using only regen and normal engine operation (i.e. no CHG mode). But that's just for an experiment. The cost of burning gas to charge the traction battery is higher (less efficient) than just burning gas to drive the car as a regular hybrid Prius.

 

you'vve nailed it after one day vs years of ownership by some who are still clueless

 

Where does it go? Into the battery. There is a big hysteresis (for lack of a better term) between the HV and EV states of charge in the traction battery. So, if you're going down a mountain (Pikes Peak and Mt. Evans were great examples) with a depleted EV range, it will eventually show several tenths of a mile range. I don't remember the exact number but it's well over 0.1 miles. But it takes a long descent or else some determined trickery on level roads using gas to accelerate and the stop in rapid sequence.

Rest assured, the braking energy is going into the battery exactly the same way in both HV and EV modes no matter what the SOC unless the battery is really full. Just drive it. Let it do the thinking.