Does the rear motor provide regen braking

Yes... If you do a google search you will find our discussion on that subject... Basically stopping a car's forward momentum puts the majority of all the load on the front brakes with a very small amount of load on the rear brakes. Thus, braking via the rear motor will provide regen but such a little amount that people wonder if its working. It's working, just not that much.

 

huh, i didn't realize all the regen was not happening inside the e-cvt anymore

 

Never really was. The traction motor does the braking, and it connects to the drive train just past the transaxle. IIRC, it connects to the ring gear.

 

MG2 still deserves credit as part of "the e-cvt", though. It plays an indispensable role in how power going in at the engine end arrives at the final-drive end.

It absolutely deserves credit as part of "the transaxle", which includes everything from the input shaft to the differential.

Whether MG2 connects to the ring gear directly or through a reduction stage depends on the Prius generation.

 

I've always thought of transmissions and differentials as separate components. The transmission manipulates the engine output, and the output from it goes into the differential to divert the propelling force between the two drive wheels. I now see that a transaxle is the transmission and the differential, usually of FWD cars.

eCVT to me is the transmission section alone. MG1 is part of it has its main job is to simulate those variable gear ratios. MG2 is mounted in the transaxle case, but it is only applying motive or braking force. It could have been mounted outside the case, like the engine, and still do its job. Replace the MG2 with a resistor bank, and the eCVT could still perform its transmission duties. That would just be a really inefficient way of doing a transmission for an ICE car.

Since everything is stuffed in one case, transmission, eCVT, and transaxle can easily end up used interchangeably.

 

It sure would: your thought experiment produces a very different, and disqualifyingly inefficient, not-really-transmission.

Replace MG2 with an open circuit, and you have no transmission at all. No sink for power generated by MG1, therefore MG1 freewheels and no power goes through.

Replace MG2 with a resistor bank, and now at least there is a way for MG1 to do its job—but the electrical power MG1 generates while doing that is flat-out wasted, and that's a substantial fraction of the power that went in, gone.

A 'transmission' is generally taken to be something that gives you the same power out that went in(*), at possibly a different combination of RPM and torque. Replace the resistor bank with a real MG2, and now you've got a 'transmission', as both the mechanical and electrical power paths rejoin at the output, giving you the same power out that went in(*), making it a genuine transmission. Without MG2 included in the picture, it isn't.

(*) save for small practical losses

 

Interesting! What more does my Prime do for regenerative braking? It has 3 different settings (intensity) for regenerative braking. Not sure I see a difference in battery range. Very noticeable difference in driving tho.

 

Not sure where that thread went? I'm unable to locate it... But the discussion happened in this Gen5 forum last Spring.

 

General questions here are usually loaded and regen questions are loaded even more often.
It might be better to first understand exactly what the motor on the back wheel is used for. Than it's a bit easier to understand if it adds and how much it might add to the overall regen.

The answer might also be different for the EV 4X, Plugin and Regular Prius. One thing for sure is that's it's not an easy question to answer on any level, much less a general one.

 

It's likely those settings just alter some curves programmed into the ECU for how much regen to apply according to your pedal position, to suit your personal preference, rather than making any technical change in how the regen is done. The gen 3 offered normal, power, and eco driving modes, same kind of deal.

 

Ill say this... if anyone is interested, I've developed an obd2 dongle with an sdcard slot that's used for logging your vehicles data without the need for a phone or tablet... I need people who are interested in stepping outside the box and willing to log their vehicle data.

You see, after installing upgraded brakes on my PHEV, the rate at which energies are stored while braking significantly increased.

 

The Tactrix Openport 2.0 also has a card slot and can do the same thing.

 

yah, but have you attempted to use one to log data to the sd card yet?

not to say that device isn't one of the fastest to communicate with techstream that I've used, it just doesn't do what I need it to... a way to pull from canbus the data my rear motor controller needs to power it self and I had to make my own obd2 board.

now.. i need to spend some time to see if one of these 433MHZ receivers/transmitters can read the TPMS sensors that work with these cars while attached to this board. i was able to read the techstream data in pass through mode but... i haven't figured out techstream working through Bluetooth or wifi. wouldn't it be nice to retrieve techstream dtc info through a nice web GUI or have a pdf report auto-emailed to you when MIL is illuminated?

 

The answer is probably no.

In Prius/Prius Prime, the limiting factor in regenerative braking is the battery C-rate (charging rate, 1C = 0–100% in 1 hr), not the electric-motor power in kW. The C-rate is probably limited to about 7C to preserve the battery life. For a 1-kWh (Gen 4 or Gen 5) Prius battery, this would be 7 kW, and for a 9-kWh Gen 4 Prius Prime battery, it would be 63 kW. Nevertheless, I doubt Gen 4 Prius Prime is capable of more regenerative braking than Gen 4 Prius (similarly for Gen 5). Moreover, Prius Prime does not come in AWD.

 

yeah but I've made a conversion kit so they can be AWD...

 

So…thus….thusly might there be any advantage to selecting level 1, 2, or 3 for the regenerative braking option on my new Prime? Should I bother to even switch it on?

 

As far as I can tell, that only makes a difference in the B mode of the shift lever. All it does seems to be to change the point where you would have to apply the brake pedal in the B mode to further slow down. It does not seem to alter the maximum available regenerative power. In that sense, it is the analogue of the eco/normal/power modes on the accelerator pedal. It does not really change any vehicle function but modifies the pedal feeling—that is when you need to switch from one-pedal to two-pedal driving in this case. You can have the exact same regenerative braking using different levels as long as you switch from one- to two-pedal driving appropriately in the lower levels.

For higher fuel efficiency and longer BEV range, it is usually recommended to avoid the B mode. The B mode is mainly for the convenience of one-pedal driving. Use the brakes gently when slowing down so that the friction brakes are not activated, and you will never need the B mode but achieve higher fuel efficiency and longer BEV range than in the B mode.

 

One of the Predictive Efficient Drive functions provides a kind of light automatic B mode - it learns where you tend to decelerate and then automatically increases the no-pedal drag each time you approach that spot, in some sort of attempt to make you come to a smoother stop, rather than braking later.

Effect is pretty subtle though - I don't think I've seen it's as heavy as level 1 of B. Does seem to be somewhat variable - possibly looking at how fast you're going and your location, rather than a simple on/off.