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Discussion Starter · #1 · (Edited)
I know many of you here will wonder what the Clarity PHEV does for engine heating. The owner's manual says nothing of course other than the car won't start if battery drops to -22 F (similar to Volt).

We had a huge drop in temperature just in time for Christmas, and yesterday morning was around 6 F and the high went up to 12 F (according to car). The engine didn't start at all. However, my wife had it start the engine on her one night at 8 F and another at 4 F.

Once started, the engine will cycle occasionally like the Volt does. The only in car indication of this event is the "EV" text on the dash goes away and the power diagram will show the engine providing power to the motors and/or battery. I need to get my OBDII scanner hooked up to it to see if I can see conditions that cause it to cycle, but I haven't gotten that far yet. However, I think I can say that in general it won't run coming from an attached but unheated garage unless the temperature is somewhat below 10 F.

More interesting to me is I think the car might have a heat pump, as the heater is blowing warm air about 50 feet from the house, with no preconditioning. The electric heater in the clarity seems better to me than the 2012 Volt. The Clarity will get sweaty and uncomfortably warm even when exterior temp is less than 10 F (but especially around 20 or 30F), with no engine help. Just like the Volt, range is reduced, but I don't think as dramatically as my Volt. When I had ERDTT disabled in the Volt I would get 15 mile range if I sat around at all with the heater on.

It is easy to drive the car without starting the engine even in very cold, but a quick stab of the go pedal will almost always start the engine, especially if speeds are higher (like 55 mph plus). Again, you watch the tach like needle around the outside of the speedo and if it passes the end of the blue the engine will start.

So to reiterate, the range seems less impacted than my Volt in the cold (at least slightly, still heavily impacted), and the electric heater seems more effective. The car does have ERDTT, that kicks in at somewhere under 10F, not entirely certain on conditions since it ran for my wife at 8F, but not for me at 6F. So far my range is around 25 to 35 in the winter, with a lot of "idling" (heater drawing power but not going anywhere). I haven't driven it cold soaked yet, which will be a good indicator of heater performance. I also need to test without sitting around with my Son doing Pokemon raids wasting battery charge ;)
 

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Does the manual saying anything about ERDTT?

My Bolt's heater also kicks in fast and hot. Rather than a "hair dryer" resistance heater, it uses a Eberspaecher heater similar to tankless hot-water heaters. The electrically warmed coolant circulates through a heater core just like the ones in every combustion-powered car. But it heats up way, way faster.
 

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Discussion Starter · #3 ·
No, unfortunately. Nor about heater system design (resistance vs heat pump).

If anyone is looking for the manual, Honda has it on their site:
http://ev.owners.honda.com/Clarity/ModelInfo/PlugInOwnersManual?pageMenu=PlugIn

I think since they advertise it as a hybrid EV instead of a range extended EV they are less concerned with advertising why the engine is running, and instead just state that the engine can run sometimes. My hunch is when it needs to do a fuel or engine maintenance mode it will just run the engine more and not advertise, but not positive either since I haven't seen one yet ;)
 

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Would be interesting to know more about how Honda handles this. I suspect you're right that since it's sold as a "hybrid", full electric performance is less of an issue.
 

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Discussion Starter · #5 ·
My Bolt's heater also kicks in fast and hot. Rather than a "hair dryer" resistance heater, it uses a Eberspaecher heater similar to tankless hot-water heaters. The electrically warmed coolant circulates through a heater core just like the ones in every combustion-powered car. But it heats up way, way faster.
Interesting, so noticeably faster than the Volt (Gen 1)? The Volt isn't bad, but still takes a couple minutes.
 

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Interesting, so noticeably faster than the Volt (Gen 1)? The Volt isn't bad, but still takes a couple minutes.
Way faster than my 2011 Volt. The Bolt is cranking out heat within a few hundred feet of leaving the garage. And we'd still be shivering in our ICE vehicles way past that point.
 

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Discussion Starter · #7 ·
Way faster than my 2011 Volt. The Bolt is cranking out heat within a few hundred feet of leaving the garage.
Okay, so that is likely similar to what this Clarity is using then as well.

However, I did just find this buried on the Honda page, could be a copy paste error from Clarity EV though, as this is a feature they might want to advertise:
How do I maximize my range when driving the Clarity Plug-in Hybrid?
The Clarity Plug-in Hybrid features energy-smart climate control technologies, an efficient Heat Pump, eco mode, and multiple levels of regeneration to help maximize your driving range.
It is buried at FAQ at bottom of page under Driving Range.
https://automobiles.honda.com/clarity-plug-in-hybrid#maximize-range
 

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...The car does have ERDTT, that kicks in at somewhere under 10F, not entirely certain on conditions since it ran for my wife at 8F, but not for me at 6F...
Thanks for the information.

Is it possible you wife may have pushed the go pedal passed the detent which is why it came on, instead of due to the cold temperature? Just wondering how easy it is to exceed the threshold if you are not watching it like a hawk.
 

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Discussion Starter · #9 ·
Updated my review with some cold weather impressions. ERDTT mode is definitely very different than the Volt and appears it might be based on battery temp, with maybe an absolute switchover from temps less than 0F.

ERDTT mode on the Clarity is more like driving in hybrid mode. It will still use the battery, but run the engine continuously as well. This makes it a little less annoying than the Volt that switches back and forth, but also might run the gas engine more. I think the overall fuel usage will be similar, although I appreciate that the Clarity runs at a higher temperature. I don't really like that the Volt doesn't warm up fully in ERDTT and essentially uses the mode only for waste heat.

https://carswithplugs.wordpress.com...-part-2-impressions-and-cold-weather-driving/
 
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