If I was you I would insist on technician telling me all error codes, this could help in the future if other problems show up. Poor power output could mean poor electric connection, failing battery etc. indicated by "check hybrid system", or poor ICE output (bad gas? stuck EGR valve etc.) suggested by "check engine" light. During highway driving, computer will decide if you need more power from ICE or battery, so unless you're driving down the hill or close the throttle to let the car coast, battery charging is not given, it could as well be discharging to help ICE, especially if driving against the wind, up the hill etc. I would keep close eye on the car, but otherwise have no other advice. I don't remember reading anybody else complaining about similar issues, so don't think it is something common. Hopefully your car has typical (at least in US) 36k warranty and whatever it is, it either fixed itself or fail altogether before warranty expires, without too much inconvenience for you. Try to find longer downhill run or any place where you can safely coast at high speed, to verify for sure battery is not charging at high speed, it would be most troubling if true.

 

I thank you all for your replies, greatly appreciate your help.

Pete4, thanks. I will get the error codes from the technician and share with you all. I will also keep an eye on the car. It’s due for oil change now. The scary bit above all is the ICE not charging the traction battery at relatively high speeds. SteveHanson, could that be the result of the relatively high temperature in my area? I guess I need to better understand the workings of the traction battery and the factors that affect its performance. Any bulletin from Toyota on this will be helpful.

Thank you all.

 

When the battery temperature is high, it does slow down the charging to protect the battery. The battery makes heat when it is used, both charge and discharge operations generate heat. And ambient temperature contributes to battery temperature by setting the base temperature. The battery is in air-conditioned space -- it gets conditioned air through the duct on the rear shelf. But it takes time for the AC to cool a car that has been parked in the sun. The battery is in the last compartment to get the cooling, and it has a lot of mass. So, yes, a high ambient temperature can cause variations in behavior.

The dealer can scan the codes and run the diagnostics. If there is actually a problem, that should detect it. Otherwise, I suspect the problem might be just a mismatch between your expectations and reality. These cars hardly ever fill the battery all the way full, by design. I stopped worrying about mine a long time ago.

 

It's true that the car's battery is never fully charged all the way to the top. But I still get it charged up until the green bars comes up- that's one bar short of full charge.

Is there any link/article to back up your reasoning that the ambient temprature contributes to battery temperature? I have kept a closer look at the car's performance in the past weeks. No noticeable difference. It still takes longer time to charge the battery and there's no charging the battery at high speeds.

The technician who helped diagnose the problem with the car is out of town and cannot be reached at the moment. Thanks.

 

You shouldn't be charging the car to above 6 bars (blue bars) under normal usage unless you're braking for a prolonged time. 6 bars is the car's ideal state, and anything outside of that is sub-optimal for the long-term life of your battery. Anything wildly outside that (below 1 bar or above 8 bars) is very bad for your battery's long-term life, but the computer more or less prevents you from ever getting that far.

At 100kph, cruising smoothly, what's supposed to happen is the engine is revving high to maintain high speed, even though that same high rpm is excessive in terms of power - the engine is keeping up with the wheels, but producing more power than needed at that high rpm. To make this more efficient than a normal car, it dumps this waste energy to the battery by having the electric motor resist the gas engine slightly (this is called "Heretical Mode" on priuschat.com). This increases how much energy is in the battery, potentially getting it above 6 bars - BUT:

Before it gets from 6 bars to 7, it very briefly cuts the gas engine down to idle, and pushes with the electric motor, so your primary torque is now the electric motor instead. This drains off the excess energy accrued during the gas motor high-rpm phase, and drains the battery back down to the low end of 6 bars. The gas engine then resumes its high RPMs and the electric motor begins resisting again, repeat.

The result is that you're basically driving a normal car most of the time, except that the waste energy of the gas motor isn't just being lost - it's used to reduce gas usage, albeit in repetitive short bursts.

So - what's odd isn't that it isn't getting to 7 bars driving at high speeds, but rather, that you were regularly getting it to 7 bars before. Judging from your original post you seemed to feel 7 bars was desirable, so I suspect you were going out of your way to get to those 7 bars.

This is a common misconception of many first posts on this forum, and at this point in my mind a user interface design mistake by Toyota - the display makes it look like higher is better and many users seem to try to get those higher battery numbers, when that's actually undesirable. A more intuitive display would be one showing a battery meter that shows a "Good" label in green in the middle, "High" in red to the left, and "Low" in red to the right, with an indicator that moves between these labels. Then the user sees the goal of balanced battery charge just from glancing at the readout.

 

First of all, there is very little one can do during normal driving to charge or discharge the battery, since it is under computer control, so the statement about not charging the car above 6 bars, is a little bit of a stretch. Also there is no good or bad state of charge for the battery, again it is under computer control which keeps it, if my memory serves well, between 40% to 80% of full battery charge, which is optimal. As far as I know the gauge on the TCH display shows that 40% with one bar (empty) and 7 bars for 80% (full) and the computer won't allow, if it can, to let the battery go out of that optimal range. So properly functioning car will keep battery state of charge at proper range (40-80%) and there is no bad or good level here.
There is a question of calibration:
a) How computer knows the battery is at let's say 80% full charge
b) how is that translated into bars
So maybe the issue is of proper calibration.
As far as heat is concerned, this could be a problem: a car parked in sun could heat up all the way to 150-160F, battery has a resistance and flowing current will heat it up more and at some point the battery could fry. To avoid that there is fan to cool the battery and there is thermal protection build in, so I would check if fan is working and use AC when driving. There could be some poor electric connection that heats up pack and triggers thermal protection, which I would imagine would lower amperage input/output but there really is no easy way to test it. I really would go to the dealer and first read the codes, if there are any and also monitor the car while driving with the tester, there is a lot of info about operation of the car and it could indicate if anything is out of ordinary.

 

Thanks Peter. Your advice about getting a dealer to sit/drive the car with me is what I'll do. In the past few weeks, battery charging has deteriorated rapidly.

 

The local tech here once told me he never had to replace a traction battery under 200,000 miles. He also said, that if you have a single cell go bad, the display will notify you. I forget to ask if it's the check engine or the MFD.

 

Some observations:

1. The regenerated energy from the regenerative breaking process has been consistently lower than the normal 50Wh. It's halfway - 25Wh for some 2 months now.
There could be a problem with the charging assembly. What that is, is what we're yet to find out.

2. Temperature seems to play a role here as stated by one of you earlier on. We're approaching the rainy seasons and temperature has gradually dropped by some 5 deg C on the daily average. I noticed that when it's cool out there charging by the engine takes less time. But at other times when it's hot, battery SoC remains low for longer duration. However, regenerated energy remains poor.

But I still can drive the car around and fuel consumption is great compared to other big sedans in its class.

Technician have scheduled the car for another check next weekend when he's fully armed with the other tools to loose some parts and do a thorough.

We're just two with the TCH in my locality.

 

Mine is just the opposite. I find my traction battery charges much faster and drains slower during the warm months.

During the winter the traction battery seems slower to charge. It seems to drain down faster when in the EV mode.

You should find the regenerated energy is strongest when the traction battery is lowest at 40%. It's least when the battery nears it's 80% full charge.

in your earlier message you worry about the last bar not showing a full charge. That's the 20% of the battery that's reserved so the regenerative braking can work properly when the battery is charged at 80%. I may have mentioned it earlier. The generator will not charge the battery when your driving at 80 miles per hour or faster unless it's definitely needed.

I doubt they will find a problem with your TCH, if your check engine light is not lit with a trouble code.