Stan,

On the Prius, the SOC display only shows states between 20% and 80%. This is actually better as the divisions each equal 10%. So, when you are at two bars, you are really at 40%, not 20%.

I would think this is the case on the Camry as well because as the state of charge goes down, so does the volts per cell. After that, you have to increase current in order to compensate for the decreasing voltage. The system is set up to prevent over-current situations by starting the ICE and the charge cycle.

I am taking a huge leap on this, but I am guessing this is also why there is 2.5 - 3 gallons left when the light comes on. People have run the Prius out of fuel and still had enough electric juice to go 2 or 3 miles at 30 MPH to get gas. I would absolutely not try that in the Camry. It is less aerodynamic, and heavier. Once the state of charge starts to drop you could very easily reach a point where the thermal system, or the low-voltage disconnect, engage to keep the battery from damage. I do not know if those will reset automatically or not.

 

Bigsk8r — The Camry's SOC display has 8 bars, but they represent a range of only from about 40% to about 80% of the NiMH battery's total charge capacity, as I understand it. This is all that Toyota will allow one to use, for increased battery reliability and longevity. This is similar in principle, if not in absolute numbers, to what the Prius does. What I was saying is that each of the 8 bars displayed represents 12.5% of the USABLE battery charge, and as such, the SOC reading error could therefore be as much as +/-6.25% of the USABLE charge. Sorry for any confusion.

Stan

P.S. I have added information to my post #70, 5th paragraph, about the ICE rpm change that I find accompanies its "gear change" during warmup.

 

Further information:
One other point that's interesting to note: When coasting at speeds above 60 km/h (~40 mph), the FE gauge reads precisely 0 L/100 km (60 mpg) and the ICE symbol is not present on the Multi-Information Display (I have a non-NAV), but nevertheless the ICE IS still ticking over at ~900-1000 rpm and consuming fuel. According to my ScanGaugeII, it is consuming fuel at the not-insignificant rate of ~1 L/h (~0.26 galUS/h). The only time the ICE is truly "off" is when the FE gauge reads in the blue "EV" area. I wonder why Toyota doesn't display the fact that it's still using fuel? (I guess they also don't show the ICE symbol when the vehicle is stationary with its ICE running, but the FE gauge DOES show fuel being used in this case.) Is the more elaborate display in the NAV TCH better in this regard?

Stan

 

No not really.

I have notice times that the ICE is running, and the arrow does not show it doing anything. I wonder if that is just fuel being thrown out the window or if it is charging the battery.

 

That is kind of odd. If you were able to coast for 65km in that scenerio (about 65KM per L) that is still about 1.5L/100km. I have seen both situations when coasting where the needle is dead on 0L/100km or gently floating at 1 or 2L per 100KM. I had always assumed that "0" meant no fuel and ICE was spinning to protect the generator and the other meant just a tiny bit of fuel to idle the ICE.

Since the US model gauge bottoms out at 60mpg or 3.9L/100km this might only be witnessed on the Canadian model.

 

ag4ever — At higher speeds I think they have to keep the ICE running to prevent MG1 from over-revving. Its power output is probably not being wasted, as it's fed into the power-split device and goes to MG1 (and hence the NiMH battery). At lower speeds they may keep the ICE ticking over so that it's available without any start-up hesitation whenever it might be needed. Again, its power output is presumably not being wasted, but I can't say for sure. The annoying thing is that if I'm coasting at say 100 km/h, and the ICE is ticking over and using fuel at the measured rate of 1 L/h, then it's contributing 1 L/100 km to my FE, but the FE gauge shows precisely ZERO (metric version!). [The FE display can easily show usage as low as 1 L/100 km on its scale, and at other times it DOES show such low readings, but not under these conditions. I wonder why?]

Stan

 

Correction — In my Post #70 I said that I'd only noticed the "gear change" effect during the initial warm-up cycle. This is incorrect. Taking more careful note, I find that it DOES occur even after warm-up is complete. I don't have a handle on the precise circumstances. I STILL believe, however, that this is NOT an indication of poor FE in certain speed ranges. I find consistently that this effect occurs when driving AT A CONSTANT SPEED up a slight incline. I suspect that it happens even on the flat, but it would then be less noticeable, since the ICE load and rpm would be lower when it happens, and the changes would therefore be smaller. I believe that it's a change being made to the TCH's power distribution strategy. Since it does NOT require a change in the vehicle's speed, it CANNOT represent the vehicle moving from a speed at which the FE is low to one where the FE is higher.

Stan

 

I notice it a bunch, and have chalked it up to a "full" battery where the computer feels it is advantagous to give the car a boost with the MGs to chew down some battery.

 

ag4ever — I think you're on the right track. The TCH seems to change its strategy when this happens. Perhaps it was until then busy using some ICE power to charge its batteries, and has now switched over to a more normal ICE load, allowing more use of the NiMH battery for power boosting, and requiring reduced ICE power output. Because that's what seems to be happening — the ICE's rpm, % load, and fuel consumption all drop substantially when this "gear shift" occurs.

Stan

 

I've been monitoring the "gear change" effect these past few days, and I find that it occurs at all constant speeds between AT LEAST 50 km/h (~31 mph) and 75 km/h (~47 mph). I'm SURE that it's NOT an indication of lower FE in this speed range, since when it occurs I'm still in that same range — it's not triggered by speeding up or slowing down. At those times when it's felt most clearly, I've noticed that the "battery assist" arrow has also just come on at the same instant. Sometimes my TCH actually goes BACK AND FORTH between these two modes (poor FE and good FE), at least in the very cold weather we've been having here recently.

By the way, when the ICE is "off" but being spun by MG1 (to prevent the latter from over-revving), the thermodynamics tells us that the intake air is actually being COOLED by passage through the engine because the expansion stroke is longer than the effective compression stroke in these engines! So the ICE acts as a refrigerator under these conditions! Its exhaust air is actually cooling the catalytic converters down!

Stan