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Anybody else noticed this: ????

It was extremely cold this morning when I left for work (car was reporting -29 C), and aside from everything being stiff, I noticed that I had virtually no regen braking for a good portion of my commute, i.e. the car offered very little braking on the initial portion of the brake pedal travel and I could tell from my scanguage that the battery was not being recharged much, even by the engine. Eventually everything came back to normal, after about 25 km of driving (and I assume after the battery warmed up some).

I'm assuming that it's normal behavior, as in something to do with protecting the battery, but that explains the dismal FE number that we get in the cold.

I'm just interested in hearing if anyone else has witnessed the same?

Yves
 

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Anybody else noticed this: ????

It was extremely cold this morning when I left for work (car was reporting -29 C), and aside from everything being stiff, I noticed that I had virtually no regen braking for a good portion of my commute, i.e. the car offered very little braking on the initial portion of the brake pedal travel and I could tell from my scanguage that the battery was not being recharged much, even by the engine. Eventually everything came back to normal, after about 25 km of driving (and I assume after the battery warmed up some).

I'm assuming that it's normal behavior, as in something to do with protecting the battery, but that explains the dismal FE number that we get in the cold.

I'm just interested in hearing if anyone else has witnessed the same?

Yves
I drive in cold weather, and I have not noticed it. Will try and watch for it. You can normally tell how much regeneration there is by watching the ECO gauge. When it goes negative it is charging the battery. It makes no sense that the battery would not be charged. What I have noticed is that the ICE loads up when it is cold and you are stopped at a red light. The only way of loading up the ICE above normal idle is to have it charge the battery.
 

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I drive in cold weather, and I have not noticed it. Will try and watch for it. You can normally tell how much regeneration there is by watching the ECO gauge. When it goes negative it is charging the battery. It makes no sense that the battery would not be charged. What I have noticed is that the ICE loads up when it is cold and you are stopped at a red light. The only way of loading up the ICE above normal idle is to have it charge the battery.
Well, that's kind of my point: the ECO gauge needle was dipping in the negative, but not much charging or braking was happening.... also, I started my commute with a battery at 52%; it went down to around 50% and stayed there for the first 20 km or so... with lots of braking involved during that time. Also, the engine never shut down the whole time, and it never charged the battery enough to bring the charge state up to its normal 60%.
Things got back to normal as soon as the inside of the car got warm, hence my comment about some kind of temperature limit for charging.

Yves
 

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I parked the car in my heated garage last night (10°C) and I saw the outside temp gauge reporting -27°C a few minutes later while driving to work. That allowed me to get good EV and regen considering the temperature (with minimal heater use when stopped). Finished at 6.8l/100km after 40km (tank so far 7.0l/100km in car display). I did drive the car when parked outside down to -22°C and didn't notice any loss of charging or regen braking. Maybe it wasn't cold enough then.

The cold weather and frequent snow falls (and lots and lots of bumper to bumper driving) is definitely taking a toll on the fuel consumption.

Yves, I haven't transferred my Scangauge into the Camry yet (used to have in it my Civic Hybrid). Are you using the Gen3 Prius XGauge codes to read all those nice parameters? During the Xmas holidays, I have to find the time to install the ScanGauge in the Camry... Where did you install it? I can't see any good spot except maybe on top of the steering wheel stalk.
 

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I agree with YvesJ and wonder if it is indeed detrimental to traction battery life to pump a lot of charging current through an extremely cold battery. This is just a supposition on my part -- I really have no idea if it is the case in reality, but it would be instructive to find out. I've always wondered about how temperature extremes affect the traction battery's life.
 

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The other night we drove off to go to town. I did have the block heater turned on for near 3 hours earlier due to the upper 20's temperature. I started the car after removing the extension cord. First I looked at he Scan Gauge to see the water temp was only up to 80 degrees. Most times it's around 105 or 110F degrees when it's a little warmer outside.

I drove out the 200 foot driveway stopping at our mail box out on the road were we live. The engine kept running while stopped. Once about 500 feet down the road the engine auto shut off and went into the EV mode. I looked at the scan gauge coolant temp again as it read 103 degrees. I had never seen it go into EV around that low of outside temp.

I remember the '07 TCH I had owned earlier, the EV would not come on till the temp was up around 130 or so degrees, best I can remember.

I have noticed using the block heater on this '12 TCH the engine does heat up somewhat quicker than when I had the '07 TCH which also had a block heater. Could be when it's really cold outside the ECU keeps the water pump shut off to prevent bringing in the ice cold radiator water till the engine has warmed up maybe to 150 to 160 degrees. Seeing it hit 179 degrees after driving 3 or so miles on the main highway sure looked good. I do turn the heater on low fan once I see it's up around 130 deg. I go to 2 graphs on the fan once the engine is in the 170 deg range to fully heat the cabin.

I read about the '12 having some exhaust method to help heat the coolant, but I forgot how that works.
 

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I parked the car in my heated garage last night (10°C) and I saw the outside temp gauge reporting -27°C a few minutes later while driving to work. That allowed me to get good EV and regen considering the temperature (with minimal heater use when stopped). Finished at 6.8l/100km after 40km (tank so far 7.0l/100km in car display). I did drive the car when parked outside down to -22°C and didn't notice any loss of charging or regen braking. Maybe it wasn't cold enough then.

The cold weather and frequent snow falls (and lots and lots of bumper to bumper driving) is definitely taking a toll on the fuel consumption.

Yves, I haven't transferred my Scangauge into the Camry yet (used to have in it my Civic Hybrid). Are you using the Gen3 Prius XGauge codes to read all those nice parameters? During the Xmas holidays, I have to find the time to install the ScanGauge in the Camry... Where did you install it? I can't see any good spot except maybe on top of the steering wheel stalk.
Unfortunately, my car sleeps outside... I got something like 8.7 yesterday, but as I said, with no regen and the engine constantly on, what can you do? When the temp is around -10C, I can usually manage a 7.2 - 7.3.

The only special scanguage code that I'm using is for the battery SOC parameter, and yes it's from that list for the Prius. I had to do it twice as my scanguage reset itself to its defaults while doing the programming. Mine is on the steering wheel stalk, which is pretty much the only good spot for it.

Yves
 

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Got a 5.5l/100km this morning after parking the car in the garage and driving in -13C weather. Best I got in a long time now.

The cold weather probably affects how the traction battery gets used and recharged. I know it certainly did in my previous Civic Hybrid. On very cold days, the engine would first start from the normal 12V starter and there was practically no charging, no regen, no assist and no auto-stop until the car warmed up (and not just the ICE).
 

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dborn,

You asked mounting location of Scan Guage.I mounted mine on steering stock. It has a curve to it, and I used some left-over small round 3M Dual Lok tabs I had left over from my motorcycling days(used to mount headlight protector).

I put one on each side of the bottom of SG and it raised it up just enough to clear the curve in the steering wheel stock.

It has been in place 6 months and is a good location.
I programmed in many gauges, including RPM, Battery temp, battery SOC, coolant temp, charging rate, instant mpg, tank mpg, fuel trim and a few others.

In this cold weather, I've been watching coolant temp. and it is interesting to see how much it cools when in EV mode.
 

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Yeah, that sounds like it's the best place to mount the SG (by the way, what's the name of that "box" just ahead of the steering wheel? stalk? stock? other? sorry english isn't my first language).

In my Civic, the temps went down from 90C (normal operating) to 67C with the heater on and engine in "auto stop" mode, when the engine would start back up. It didn't take that long to lose 23C!
 

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Well, that's kind of my point: the ECO gauge needle was dipping in the negative, but not much charging or braking was happening.... also, I started my commute with a battery at 52%; it went down to around 50% and stayed there for the first 20 km or so... with lots of braking involved during that time. Also, the engine never shut down the whole time, and it never charged the battery enough to bring the charge state up to its normal 60%.
Things got back to normal as soon as the inside of the car got warm, hence my comment about some kind of temperature limit for charging.
The ECO gauge going negative is a measure of the charging current. The only place current can go when you are braking is into the battery. When accelerating it can divert the current to drive the wheels, but obviously not when braking.
 

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The ECO gauge going negative is a measure of the charging current. The only place current can go when you are braking is into the battery. When accelerating it can divert the current to drive the wheels, but obviously not when braking.
Obviously, whatever charging current (if any) didn't get to the battery in this case, so we're back to square one. I just found this link that confirms my experience: cold batteries cannot accept much charge, and Tesla turns off its regen braking completely while the battery is getting warmed up:

http://m.technologyreview.com/news/522496/electric-vehicles-out-in-the-cold/

I'm sure that Toyota has a bypass load in place for when the battery cannot accept a charge.

Let it be known that the TCH has some form of battery protection that disables regen braking when the battery is somewhere below -25C. For garaged cars, that's likely not an issue.

Yves
 

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Obviously, whatever charging current (if any) didn't get to the battery in this case, so we're back to square one. I just found this link that confirms my experience: cold batteries cannot accept much charge, and Tesla turns off its regen braking completely while the battery is getting warmed up:

http://m.technologyreview.com/news/522496/electric-vehicles-out-in-the-cold/

I'm sure that Toyota has a bypass load in place for when the battery cannot accept a charge.

Let it be known that the TCH has some form of battery protection that disables regen braking when the battery is somewhere below -25C. For garaged cars, that's likely not an issue.
I have never heard of any system that bypasses the battery at cold temperatures on the TCH. Tesla uses LiIon batteries, while Toyota uses NiMH. It would be unnecessary in any case as all they would have to do is disable the generation and rely on the disk brakes only for braking.

High temperature is a problem for NiMH batteries and that is why Toyota provides a cooling system for the battery.

The Scangauge is an interesting tool, but I would not bet my house on the accuracy of all the readings. I've seen some Scangauge readings posted which make absolutely no sense.
 

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I have never heard of any system that bypasses the battery at cold temperatures on the TCH. Tesla uses LiIon batteries, while Toyota uses NiMH. It would be unnecessary in any case as all they would have to do is disable the generation and rely on the disk brakes only for braking.

High temperature is a problem for NiMH batteries and that is why Toyota provides a cooling system for the battery.

The Scangauge is an interesting tool, but I would not bet my house on the accuracy of all the readings. I've seen some Scangauge readings posted which make absolutely no sense.
You're right, I've been hallucinating all along; it must have been the cold weather.

Thank you for your input.

Yves
 

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Here's an interesting article on charge rate vs. temp of the various battery chemistries:

http://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

Of course, there is no guarantee that Toyota ascribes to or abides by these precautions. However, one thing that is clear to me: Regardless of how injurious it may be to the traction battery, it has to be employed to start the ICE, at least once, regardless of its temperature at the time.
 

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I have never heard of any system that bypasses the battery at cold temperatures on the TCH. Tesla uses LiIon batteries, while Toyota uses NiMH. It would be unnecessary in any case as all they would have to do is disable the generation and rely on the disk brakes only for braking.
Not pretending to be an expert here because I'm not, but...

Is it so far fetched an idea that perhaps when it's really cold, that most of the regen braking is turned off and most of the braking is done with the friction brakes? That seems to corroborate what Yves was saying in his original post. I guess you still want to see some usage from the battery (charge and discharge) to help warm it up and not just rely on the cabin heat to get to the battery but you'd want to stay away from massive usage like when the ECO gauge is pegged at the bottom (or the top). I would think that it's not necessarily that the ECO gauge reflects actual amps to/from the battery.

After rereading all this, I think we're all agreeing that there is less regen braking when the battery's cold. Wether we want to call it "bypass" or simply relying more on friction, less on regen (I'm guessing that's probably what Yves meant...)
 

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Not pretending to be an expert here because I'm not, but...

Is it so far fetched an idea that perhaps when it's really cold, that most of the regen braking is turned off and most of the braking is done with the friction brakes? That seems to corroborate what Yves was saying in his original post. I guess you still want to see some usage from the battery (charge and discharge) to help warm it up and not just rely on the cabin heat to get to the battery but you'd want to stay away from massive usage like when the ECO gauge is pegged at the bottom (or the top). I would think that it's not necessarily that the ECO gauge reflects actual amps to/from the battery.

After rereading all this, I think we're all agreeing that there is less regen braking when the battery's cold. Wether we want to call it "bypass" or simply relying more on friction, less on regen (I'm guessing that's probably what Yves meant...)
Here is a link to a 2002 Report on the Thermal Management of a Prius Battery. The report is critical of Toyota not providing any heating or thermal management of the battery at low temperatures. On this Prius it appears all that is done is shutting off the cooling fan. They suggest that Toyota could improve warmup of the battery by using cabin air. This in turn suggests Toyota depends on current flow through the battery to warm it up. It is possible they limit that current flow, but they clearly need charging and load current flow. It would seem like a good idea if they are doing that to use any surplus current in resistance heaters around the battery to help warm it up. No indication they are doing that. It may be something easier said than done, as their main problem is keeping the battery cool, not warm, and any blanket type heater would be a hindrance to cooling. It almost would have to be an in line (cooling) air duct heater. One thing is sure is that Toyota would only as a last resort turn off regeneration, as that is what makes a hybrid a hybrid with good fuel economy.

However this report is over 10 years old and perhaps Toyota is doing more now. No idea, as I have not seen any credible report on the thermal management of the current TCH battery.

On the ECO gauge, if negative movement is not due to current flow, what else could they be using for indication? We are half way through our second winter with our 2012 TCH and I have not noticed reduced regeneration in winter. So we are not "all" saying that. Perhaps it is just because I have not noticed it, and as I indicated earlier I will try and watch more carefully. It is -18C here today and we hit -30C or so a couple of weeks ago, so there should be opportunities to see what it does.
 

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Here's an interesting article on charge rate vs. temp of the various battery chemistries:

http://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

Of course, there is no guarantee that Toyota ascribes to or abides by these precautions. However, one thing that is clear to me: Regardless of how injurious it may be to the traction battery, it has to be employed to start the ICE, at least once, regardless of its temperature at the time.
Yes, the battery will see full starting current, and I recall reports that it can start down to -40C (-40F).
 
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