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I am new to this community but have owned a 2006 HCH II since August of 2006.
I have now driven about 19K miles since I purchased the vehicle & over that time have averaged about 50 mpg over a combination of local & highway driving.

I have adopted many of the techniques described in these forums, but have a question regarding the HCH II regeneration behavior after start-up - especially in cold weather.
Since the beginning, I've noticed that not only is glide inactive until the engine warms up, but regeneration is also inactive (ie lifting off the accelerator or braking does not charge the battery).

Does anyone know the reason for this?

On a related note, I've noticed that shifting into "sport" gear during this time and lifting my foot off the accelerator will actually engage the regenerator!
I've started doing this, since my evening commute starts off at the top of a big hill and it seems a shame to map all of that potential into heat from the break pads :-)

Does this seem reasonable or is there a good reason for shutting off the regen during warmup and this work-around may be stressing some of the vehicles systems?

One last question - does anyone know a good site to find average "actual" temperatures based on month that I can use when entering my mileage data?

Hi monmouth_se, welcome to CleanMPG. My comments below:


Since the beginning, I've noticed that not only is glide inactive until the engine warms up, but regeneration is also inactive (ie lifting off the accelerator or braking does not charge the battery).

Does anyone know the reason for this?


This is absolutely normal. Here's how it all works:

When the engine temps are below 60C (140F) the brake regeneration is blocked. Electric Assist may be used to soften the engine's "cold" power curve at speeds below 40kph (25MPH).
Autostop will only work when the engine temperature reaches 70C (158F).
The optimal engine temperature range is 70C-90C (158F - 194F). When temps reach 90C (194F) the cooling fans kick in.
Battery pack module temperature is also factored in and I have described the threshold values in a previous thread. Outside air temperature, air intake temperature and CVT temperatures also play a role.What does this all mean?

It means that if you want the engine temperature to reach the optimal value ranges to enable braking regen, EV assist and autostop sooner (if at all) then you need to install and use an engine block heater.
Once you get the engine warmed up, the other challenge is to keep it that way. If you begin to glide often then the engine will cool too fast and your glides will be too short. Blocking the front grille is one way to keep the engine bay warmed up.



On a related note, I've noticed that shifting into "sport" gear during this time and lifting my foot off the accelerator will actually engage the regenerator!
I've started doing this, since my evening commute starts off at the top of a big hill and it seems a shame to map all of that potential into heat from the break pads :-)

Does this seem reasonable or is there a good reason for shutting off the regen during warmup and this work-around may be stressing some of the vehicles systems?


I only switch to "S" when the engine is still too cold and I want an upcoming deceleration to provide regeneration as part of my SoC maintenance.

The other thing you may want to do is to switch to "N" when waiting at a stop light especially when the Autostop is absent. Leaving the transmission in "D" consumes gas at twice the rate of having it in "N". Turning off the gas engine during these times is not the best as it may allow the engine to cool below its efficient range, and then we're forced to restart the warm up routine.

Some folks may recommend FAS as one way to avoid the hit of a cold engine. This is a very good approach. Personally however, I have chosen not to do so especially when the ambient temperatures are too low and the thermal and mechanical stress is high. In my view a FAS is best for milder-cold temperatures. In cooler weather the greatest challenge is keeping the engine temps as high as possible and keeping them that way while allowing the car's systems to do their best.


One last question - does anyone know a good site to find average "actual" temperatures based on month that I can use when entering my mileage data?


This has been discussed before in this forum and you may find the thread where it is referenced if you do a search. Sorry I can't remember the web site URL at the moment.


Cheers;

MSantos

MSantos,
Thank you very much for the prompt response.

I'll definitely try to find the threads you referred to for the threshold values & temperature readings. (Would you happen to know the thread name for the thresholds - I checked all of your postings and didn't see it?)

It sounds like you also use "Sport" mode for the same application I mentioned, charging the battery pack when the systems aren't at the proper temperature yet.
Any idea why the designers let the regen operate in "sport" but not in "drive" at these engine/ battery temperatures?

But, I also noticed from another posting that the battery pack doesn't fare well if getting hit with a high charge (discharge?) when cold. Hence, the light charge at very cold temps. Assuming this is the reason for not allowing the regen to operate below the temps you mentioned - I question my own wisdom of using the sport mode to bypass this restriction.

I briefly (very) considered an engine block heater, but in NJ, it seems like overkill :-) (average deep winter temps are usually above freezing).
I definitely appreciate the guidance re: using neutral at stop lights - I've occassionally been turning off the engine when I know it is going to be a while, but I like this approach much better.

Re: your comment about cooling the engine down too fast during glides in colder weather.
I try to keep the heater off until the engine warms up to temperature, but once on - does switching to recirc mode make a difference in reducing the engine cooling rate (it seems like it should)?

Thanks again for your help,
Monmouth_se

I briefly (very) considered an engine block heater, but in NJ, it seems like overkill :-) (average deep winter temps are usually above freezing).


I use an EBH all year long in Indiana. They key is to use it on a timer for ~3 hours before you're going to leave. When the weather was warmer here, my coolant would start at ~150F which meant that I would be at >160F within 1/4 mile. I'm assuming you would see similar results in an HCH2.

Monmouth_se:

The information I have for the battery packs provided by Panasonic (used in the HCH-II and Prius) appear to recommend the low temperature charge routines to begin at 0C (32F). A fast charge typically begins at roughly 10-12C (50F-55F).

This means that the BCM will manage the charging more aggressively when the module temps are too low. However, when it is too cold the system will easily bleed the charge in the form of EV assist since that will cause the battery pack to produce heat. Charging the battery pack at slower rates under cold conditions also has the side effect of producing heat as well (which is desirable).

As long as the regen pulses remain small or short the "S" regen should not be a problem. To keep them small, I use a bit or hydraulic braking especially on abrupt decelerations. Again, I only use "S" regen when the SoC is too low and the system is bent on assisting the cold engine a little too aggressively.

Once again, heat (or lack of) is a key player in getting the car back to optimal operation. That is why, I always keep the interior of the car almost comfortable for the occupant(s) since the battery pack and IPU derive their thermal conditioning directly from the passenger cabin.
What I am trying to say is that we should stay reasonably cool during the summer months and also gently use the heater during the winter. This will help keep the battery pack healthy and in good operation.

The "re-circulation" setting will only aggravate the window fogging which then has to be cleared by kicking in the defogger. Using the defogger is a high penalty approach and should be kept to an absolute minimum. I would say adding a little heat to the cabin and keeping the fan on a lower speed setting is the ideal approach, since that will help provide the IPU with the best thermal conditioning sooner in your trips. Particularly in this case, the use of a block heater has significant downstream positive effect which should not be ignored.

Like Diamondlarry said, I too use the block heater all year round, even during the scorching summer months. So installing and using a block heater is hardly overkill as long as you leave it on for the right amount of time depending on the ambient temps.


Cheers;

MSantos

Understood - thank you both for the insights.

Regards,
Monmouth_se

One last question - does anyone know a good site to find average "actual" temperatures based on month that I can use when entering my mileage data?
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Weather Underground (www.weatherunderground.com)


Punch in your zip, then choose the month history on the left side. It pulls up a month calendar with temp and other data.