Gen 4 ICE change when travelling down hills

[johalareewi]

23 hours ago, QuantumFireball said:

That does happen, but I'm talking about a situation when you're going downhill with zero throttle.

I am talking about afterwards when you get to the bottom of the hill and the brakes are off.  The hybrid system wants to get the HV Battery SOC down below the upper limit.

23 hours ago, QuantumFireball said:

MG1 is nearly always spinning when the ICE is running, sometimes backwards :) But the wheels are primarily rotating the ICE in this situation.

I meant to say MG1 uses electricity from the HV Battery to spin the ICE when you are stationary.  It does this to get the HV Battery SOC back down below the upper limit.

 

[PeteB]

40 minutes ago, johalareewi said:

I am talking about afterwards when you get to the bottom of the hill and the brakes are off.  The hybrid system wants to get the HV battery SOC down below the upper limit...

I remember first experiencing this on a 2002 Gen 1 Prius during a holiday touring Scotland in 2005.  The Gen 1 had no EV button (introduced in 2004 Gen 2 model) and a crude HV Battery gauge with just four bars - it normally only read ½ or ¾, and very,very rarely ¼.

On some of the steep hills & mountains in Scotland, I experienced a maxed out HV Battery for the first time in 3 years and over 60,000 miles.  There was no difficulty managing the speed with the brakes, but B mode made it easier.  As Alan says, when levelling out it became like an EV for a few miles, accelerating briskly up to nearly 60 mph without bringing in the engine until the SoC dropped.  Normally, with very gentle footwork, one could get up to 42 mph (indicated) on electric alone (on level or downward inclines) if the HV Battery had sufficient charge.

For those that don't know, the HV battery gauge only shows a window of the SoC (State of Charge) that Toyota's software engineers allow the car to use - empty would really leave about 40%, and maxed out is about 80% full.  The car tries hard to manage things within that so that there always enough to aid brisk acceleration and room to receive 'free' energy when slowing down or running the engine for heat or whatever.

We early adopters faced uncertainty as to the longevity of the HV battery (especially as they were rumoured to cost £5,000 + fitting to replace in the early days), but this careful management was the key to very convincing battery life (in most cases) where phones and laptops didn't have such a reputation.

[YarisHybrid2016]

Not to forget also the Battery chemistry involved - NiMH with a long operating life, vs. Li-Ion which loses capacity at a rate of approximately 20% per annum under ideal conditions regardless of what you do (tip: if you want to store a Li-Ion Battery for a long time - charge it to 80% then throw it in the freezer - be sure to bag it first).

Quote

For those that don't know, the HV battery gauge only shows a window of the SoC (State of Charge) that Toyota's software engineers allow the car to use - empty would really leave about 40%, and maxed out is about 80% full.

Now *that* is interesting. I was under the impression empty on the synoptic = 20% charged, and full = 80% charged; this range being the optimum charge states for a long Battery life under high-cycle conditions.

[nellsey]

 

I have maxed out the Battery twice in my short ownership but have not noticed any difference in operation.

This was after fairly lengthy runs downhill but I did not have to stop. I will stop next time and see what happens.

The MK4 is far harder to max out the HV Battery

 

 

 

 

 

 

 

[Joseph D]

17 hours ago, nellsey said:

I have maxed out the battery twice in my short ownership but have not noticed any difference in operation.

Having the 8th bar illuminated does not mean it is maxed out.  It does take a while on the 8th bar to max out. The fact you notice no difference, more than likely means you were not maxed out. You will know it when you truly fill that last bar completely.

17 hours ago, nellsey said:

The MK4 is far harder to max out the HV battery

No doubt.

[QuantumFireball]

On 2017-6-2 at 11:32 PM, YarisHybrid2016 said:

...Li-Ion which loses capacity at a rate of approximately 20% per annum under ideal conditions regardless of what you do...

Maybe with crappy poorly-managed 3-6 cell batteries in laptops, not in cars ;)

My Prius Plug-in has certainly not lost 80% capacity after four years. It's probably more like 5-10%. Early 2011 Leafs can be around 25% loss after 6 years, and the capacity loss on the much more durable 2nd generation Leaf batteries (introduced in 2013) has been negligible so far.

[MEP's Yaris GS]

On 2 June 2017 at 11:32 PM, YarisHybrid2016 said:

Not to forget also the battery chemistry involved - NiMH with a long operating life, vs. Li-Ion which loses capacity at a rate of approximately 20% per annum under ideal conditions regardless of what you do (tip: if you want to store a Li-Ion battery for a long time - charge it to 80% then throw it in the freezer - be sure to bag it first).

Now *that* is interesting. I was under the impression empty on the synoptic = 20% charged, and full = 80% charged; this range being the optimum charge states for a long battery life under high-cycle conditions.

Li-Ion EV batteries are best stored at around 30% SOC if left for long periods of time.

I can also say that there has been no noticeable degrade to the traction Battery in my PiP, which is at 65k miles and probably 4 years old now (taking into account manufacture and shipping time) based on use and scan gauge checks. Modern Li-Ion batteries are a lot better than the older laptop ones, which often degraded due to sitting fully charged at above ideal temperatures.

[YarisHybrid2016]

Hmm. My information was based upon Battery chemistry and the irreversible chemical breakdown of the materials.

As far as I understood cars, they have batteries far in excess of the capacity required in order to allow for this degradation, so while the practical effects of this deterioration may not be noticed for the projected life of the battery/vehicle, it is still occurring.

[MEP's Yaris GS]

While it does happen, and I don't deny that, its certain a lot slower than you seem to originally have suggested. It also appears to be more age related than use related - shown by the state of some Nissan Leaf Li-Ion units.

[kithmo]

Maybe because the HV Battery meter on the Prius doesn't represent the full range of SOC, we don't see the effective degradation of the Battery until it gets within the range of the meter. So effectively we don't see anything until the Battery has degraded to 80%, or even less as we don't normally see a full meter. EVs however probably show the full charge range on the meter so we see the degradation on the meter. Not sure on Plug-in hybrids whether the SOC full range is shown on the meter or not, but a loss of EV range will probably be the indicator when the battery is degrading. 

[MEP's Yaris GS]

I'm using a scan gauge and real world range.

[QuantumFireball]

On 2017-6-7 at 10:31 PM, kithmo said:

Maybe because the HV battery meter on the Prius doesn't represent the full range of SOC, we don't see the effective degradation of the battery until it gets within the range of the meter. So effectively we don't see anything until the battery has degraded to 80%, or even less as we don't normally see a full meter. EVs however probably show the full charge range on the meter so we see the degradation on the meter. Not sure on Plug-in hybrids whether the SOC full range is shown on the meter or not, but a loss of EV range will probably be the indicator when the battery is degrading. 

The SOC does not necessarily reflect loss in capacity. You could for example (in extreme case) lose 50% capacity of the Battery, but still charge to 100% SOC - it's just this 100% is not the same as 100% when new. Of course with a hybrid/EV it will never let you charge to 100%.

On the first gen Prius Plug-in, the usable SOC for EV mode operation is around 23%-85% (i.e. "full" EV charge on the MFD is only 85% SOC), below that it operates as a normal Prius but won't go below around 18-20% (I forget exactly). Not letting the SOC go too high or too low helps a lot with durability. BEVs do similar - the actual usable capacity of a 30 kWh Nissan Leaf for example is only around 28 kWh.

Also, having hundreds of cells in a hybrid/EV Battery compared to <10 in typical consumer electronics (phone, laptop, etc.) makes a massive difference in adding redundancy and durability.

[PeteB]

4 minutes ago, QuantumFireball said:

...Not letting the SOC go too high or too low helps a lot with durability. BEVs do similar...

A Tesla will only charge to 80% when plugged in unless the user goes into a menu and tells it to go to 100% for the next charge, for example in preparation for a long journey.  After a single max charge it reverts to 80% until the menu item is selected again.  This is claimed to be for protection of the battery's life.

I suspect this is within a 'window' of usable charge like the Prius, so 100% on the gauge is probably not 100% in reality.

[YarisHybrid2016]

For Li-Ion they are limited by time (so PiP, Leaf, Tesla, etc..) as much as usage (charge cycles).

NiMH are a little different - they don't lose as much capacity due to age as much as through use (charge cycles), though the charge state when placed in storage does have an effect on life.

Generally speaking, batteries in cars won't suffer through storage as they are used often. You would need to store a vehicle for 6 months or more for storage to affect the Battery life. This is not the same as aging effects however.

[thecaretaker]

Well, my Prius still does it.

I tried switching to EV mode but it says EV not available (despite having all Battery lights lit up). I tried changing driving modes and it still continues to do it. Tried switching to 'B' and back to D a few times, no difference.

I had a passenger with me last week (an IT tech guy) and he thought it was very strange behaviour. The engine revs are higher than just normal charge mode. That day, even turning off and turning on didn't fix it. But I did switch really quickly while sitting at the lights.

I can't think of a way to video it to show anybody safely.

It works perfectly correctly 99% of the time. I'll just have to change my route so that I don't spend so long going downhill with the foot break pressed.

[Joseph D]

12 hours ago, thecaretaker said:

I can't think of a way to video it to show anybody safely.

Take a friend with you for the ride and get them to video it. I'd be very interested in seeing the video.

[johalareewi]

If you have a bluetooth OBDC adaptor and an android phone or tablet, you can download the (free) hybrid assistant app which can log what is going on as you drive (and display it on the screen).  You can then use the (free) hybrid reporter app to analyse the recorded data. Their website says the gen4 prius is supported.

[birdseye]

I've just got back from a trip to North Wales and experienced this problem after a long downhill run where  I used engine braking and the Battery showed full and thereafter it refused to show the little EV light for another 20 miles or so of twisty roads inc long stretches of straight level road where normally it would intermittently switch to EV unless needing to accelerate. Why would the cars computer not use this to run off the Battery access ?  The same  occurred coming back today after a long downhill run where I was in a convoy behind a wary driver and had to keep tapping the brakes  and again it ran for miles before it would  show the EV light.  Car did not appear to have put itself in B mode because i know it will prevents free wheeling

  I switched my usual dashboard view to the one showing  the side of the car and the arrows showing whether the Battery was charging or running the car and it showed still charging even though the battery showed full. A long uphill pull finally dropped a line from the battery and thereafter it ran as normal all the way home.

[thecaretaker]

On ‎24‎/‎06‎/‎2017 at 4:31 PM, birdseye said:

I've just got back from a trip to North Wales and experienced this problem after a long downhill run where  I used engine braking and the battery showed full and thereafter it refused to show the little EV light for another 20 miles or so of twisty roads inc long stretches of straight level road where normally it would intermittently switch to EV unless needing to accelerate. Why would the cars computer not use this to run off the battery access ?  The same  occurred coming back today after a long downhill run where I was in a convoy behind a wary driver and had to keep tapping the brakes  and again it ran for miles before it would  show the EV light.  Car did not appear to have put itself in B mode because i know it will prevents free wheeling

  I switched my usual dashboard view to the one showing  the side of the car and the arrows showing whether the battery was charging or running the car and it showed still charging even though the battery showed full. A long uphill pull finally dropped a line from the battery and thereafter it ran as normal all the way home.

Thanks for your post, it's not just me then. Yes, I can confirm, a long uphill pull seems to get it back working normally.

I usually come back from Ashford on my own when this happens, so when I get a chance, I'll get somebody to film it doing what it does.

[birdseye]

1 hour ago, thecaretaker said:

Thanks for your post, it's not just me then. Yes, I can confirm, a long uphill pull seems to get it back working normally.

I usually come back from Ashford on my own when this happens, so when I get a chance, I'll get somebody to film it doing what it does.

I think it's only actually done that about 3 times since I got the car in November, next time it does it and I have the opportunity to pull off the main road I'll press the EV mode button and see if it refuses to do it

[thecaretaker]

When this happens, pressing the EV button you get the message "EV mode not available" despite having a full Battery.

[PeteB]

I find EV is rejected even after has just gone into 7 bars, from braking for the roundabout as I turn into my village.  After 30 sec or so on 'natural' EV it becomes available again.

I understand one of the criteria for allowing EV mode or not is Battery temperature, so maybe this is one of the reasons.

[danowat]

I don't know if the following is relevant, or even factually correct, but it maybe......

On a facebook group I saw some discussion about the hybrid system, the Battery gauge on the dash isn't a true representation of the Battery level, the lowest level is 60% full and the highest 80% full, the usable range of the hybrid Battery is between 60% and 80% (for longevity reasons), so maybe the system 'trips out' at 80% to keep the system within usable limits? (no EV use, no charge) until the battery safely discharges to usable levels?

[PeteB]

Full on the gauge is about 80% in reality, and empty on the gauge would be about 40%.

I've never seen less than 1 bar on the gauge, but on Gen 1 and 3 I have seen all bars lit, and experienced the HV Battery 'maxing out'.  

I've yet to see 8 bars or max charge on my Gen 4 (17,000 miles so far) as I've not visited any hills serious enough to do that.  It easily lights the 7th bar after braking from high speed though.