Can anyone explain this behavior?

[aschulz261]

Earlier today, while stopped in line at a drive thru with the AC on, the ICE started due to a low SOC. In order to keep the car from "creeping", I put it in Neutral. As I did that, I noticed the arrows around the battery icon went from charging (up arrow) to discharging (down arrow. I thought that was strange, so I put it back in gear and the arrows showed that it was charging again. After doing this a few times and the arrows changing from charging to discharging based on if it was in gear or in Neutral, I figured it was just weird programming in the software, until I noticed there was a change in tone in the ICE each time the arrows changed. The rpms weren't changing but the sound was. I guess that was a difference in load on the ICE.

 

I'm guessing it doesn't charge in neutral because the load on the engine is "unacceptable" somehow, but, then why leave the engine running? I'm puzzled. Does anyone have an explanation for this?

[GrySql]

From the below examples I would say that when the gearshift is in Neutral that the ICE has no charging load. The HVB would be in the discharge mode.

 

From the Shop Manual regarding the eCVT:

Neutral

With the range selector in N:

• no power flows through the transmission.

• the output shaft is disengaged from the drive wheels.

 

and this:

'When the transmission range is in the neutral position, the electric motor does not provide power to or hold the final drive and the final drive can spin freely.'

[aschulz261]

The examples you give from the shop manual are exactly what you would expect from a transmission in neutral. I just find the fact that there is no charging load while in neutral to be weird. The ICE can handle the load in Park, and I would expect the load to be the same in neutral.

 

Does this mean that it is possible to COMPLETELY discharge the HVB with the AC on if left in neutral?

 

I can't think of any other instance where the ICE is running and the HVB is discharging and I can't understand WHY you wouldn't be charging the HVB in this scenario.

[GrySql]

The HVAC system is electric and runs off the HVB.

As far as I know, the Battery Control Module's sensors monitor the HVB's SOC and when the lower SOC threshold is reached it will begin charging the HVB, regardless of the eCVT's Neutral position.

At that point the ICE will come under load because the DC/DC Inverter is in use and you should see the 'up arrow'.

[aschulz261]

The reason the ICE was running was because of the low SOC. It had been in EV mode, and when the ICE started is when I put it in neutral.

[Easy Rider]

 

 

I'm guessing it doesn't charge in neutral because the load on the engine is "unacceptable" somehow, but, then why leave the engine running? I'm puzzled. Does anyone have an explanation for this?

I think some further testing is needed.

 

With mine in PARK, it cycles the engine on as needed to maintain a minimum SOC and runs everything off the battery as much as possible; and cycles the engine OFF when the SOC goes up enough.

 

I would expect a similar function when in N......but haven't really tried that.

 

I would think that ICE running but battery not charging is (as long as the ICE is warmed up) NOT something that should happen.

[md13ffhguy]

On the other hand, it's rarely necessary to be in Neutral, so why worry? Just leave it in Drive and keep your foot on the brake, or put it in Park, if you're going to be stopped for an extended time.

 

I used to want logical/rational explanations for everything, but I'm starting to realize that often times it doesn't matter. I just accept and move on! YMMV. ;)

[SteveB_TX]

Just accept that hybrids are inherently weird, and you will live a much happier, stress-free life! :)

[lolder]

The examples you give from the shop manual are exactly what you would expect from a transmission in neutral. I just find the fact that there is no charging load while in neutral to be weird. The ICE can handle the load in Park, and I would expect the load to be the same in neutral.

 

Does this mean that it is possible to COMPLETELY discharge the HVB with the AC on if left in neutral?

 

I can't think of any other instance where the ICE is running and the HVB is discharging and I can't understand WHY you wouldn't be charging the HVB in this scenario.

Per regulations, all cars must have a "neutral" where the car is incapable of being propelled by it's power train. In these cars it is done by removing all torque from the generator which controls the eCVT. In "N" you can discharge the HVB to an emergency shutoff level lower than what is normal. It is still enough to start the ICE. There is only one good reason to ever leave it in "N" and that is when you go through a rolling car wash. Turn the AC off first. Tell the attendants to not turn the car off and leave it in "N". Tell them if they turn it off and put it in "N" it will not start until they put it in "P". They usually hop in while it's rolling out the wash and try to start it in "N". If they don't speak your language, you're out of luck. Turn the AC off in case. I printed up an instruction sign and keep it in the "glove" box.

[darrelld]

Did you look at the hybrid screen and check the energy flow status.

[GrySql]

In these cars it is done by removing all torque from the generator which controls the eCVT. In "N" you can discharge the HVB to an emergency shutoff level lower than what is normal. It is still enough to start the ICE.

Will the car shut down at this point? Then, if you put it in Park, it can be restarted and with the eCVT generator engaged it will begin to charge the HVB?

I noticed a phrase in the eCVT manual that says:

Under certain conditions the SOBDMC will command the generator/starter to produce electricity for the electric motor and to charge the batteries.

That would not happen with the car in Neutral I guess because the eCVT is disengaged.

Edited September 29, 2014 by GrySql

[acdii]

When in Neutral, the clutch disengages, so in a sense the entire genset is disconnected. When in park the park pawl(if it even uses one), prevents any motion from the genset to be transmitted to the drive wheels, so the generator can charge the HVB. Just leave it in gear, you arent wasting anything by doing so.

[aschulz261]

Just to clarify, this is not a situation I am stressed, concerned, or even slightly worried about. It was just something I noticed and said "huh, that's weird". Then the thought came to mind about completely discharging the HVB because of it. It is most certainly not a situation that comes up very often, for sure.

 

Looking at ACDII's post above, I wonder if it is a way to ensure that there is no way power can be directed through the powertrain. Still wonder what is done with the HVB charge level.

[lolder]

Will the car shut down at this point? Then, if you put it in Park, it can be restarted and with the eCVT generator engaged it will begin to charge the HVB?

I noticed a phrase in the eCVT manual that says:

Under certain conditions the SOBDMC will command the generator/starter to produce electricity for the electric motor and to charge the batteries.

That would not happen with the car in Neutral I guess because the eCVT is disengaged.

I don't believe there is a clutch in these eCVTs. The eCVT is "engaged" all the time but the ICE can't transmit any power to the wheels unless torque is put on the "generator" which is inhibited by the computer in "N". If the ICE is running and you select "N", it will continue to run. The DC to DC converter is still on so the 12 vdc is being charged by the HVB. It runs longer that the 30 -60 sec first start checks and may run until the HVB relay opens at the emergency shut off level and the 12 v subsequently dies. You would then have to jump the 12 v to start. There will be enough energy in the HVB to start the ICE with the "generator" and the HVB will recharge normally in a few minutes. The 12 v will take a lot longer. In the 2010-12 FFHs, The ICE will not start in "N" except in one case. if you are coasting downhill in EV and "N", if you exceed the 47 mph maximum EV, the "generator" will motorize or start the ICE to keep the generator RPM below limits. Look at these demos.

 

Check the "Driving mode" box and select the function. This is a Gen I Prius but most of the eCVTs are similar with different numbers.

 

http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html?Language=en?Country=US

 

Here's another one.

 

http://www.eahart.com/prius/psd/

Edited September 29, 2014 by lolder

[hybridbear]

You can tell that the electric motors are not disengaged when using Torque Pro. The car seems to report the friction losses when in neutral.