tigger19687
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Re: Solutions for windshield fogging in cold weather?

Wed Jan 20, 2016 11:43 am

Passed by a Tesla this morning, 19 degrees out but have no idea about humidity .... I looked over to see the driver but I couldn't ................ his window was all fogged up !!

HAHAHAHHAHA Guess it isn't just us, or he is a hot guy ;)

The 'i' was clear. Course I was driving with the heat on the windshield on medium blower. It used up my battery badly so I normally don't do that.

I do NOT have a remote for the car..
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PV1
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Re: Solutions for windshield fogging in cold weather?

Wed Jan 20, 2016 12:21 pm

FrostyCanada wrote:That's impressive ... What do you do to stay warm (especially your feet)?

Winter coat and Thinsulate gloves. I preheat the car for 30 minutes, so it is usually warm enough to last the 10 miles to work. My shoes are surprisingly decent at keeping in the heat. I'm still cold when I get to work, but I figure that going from a heated house to a heated office building, I can bear 20 minutes of cold. Willingly driving without heat unless necessary helps curb the shock when driving longer distances where the decision between a cold ride and a cold walk is mandatory ;) . That behavior has also prompted endless jokes about not taking the i-MiEV because "it doesn't have heat" :roll: . You take your first 60-mile trip to the city on the third day you own the car and a precedent is set :lol: :roll: .

Heated seat is a must.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015
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jray3
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Re: Solutions for windshield fogging in cold weather?

Thu Jan 21, 2016 2:15 pm

Aerowhatt wrote:
jray3 wrote:Though I can't imagine many places with lower humidity than ABQ. ;-p

Normally I would agree with you. But ... No offense meant, but good advice should not be undermined by flip, out of context, remarks.
Aerowhatt


Sorry to be flippant Aero. I spent Christmas skiing north of you in Durango. It felt like my parched amphibian skin would split open, but the chapped lips have finally healed.

I'm not a refrigeration engineer, but here's a psychrometric chart that'll get us pretty close.
http://www.coolerado.com/pdfs/Psychrmtrcs/5000Psychrmtrc11x17.pdf

Since mountains are in our mix, I picked 5000' altitude and saturated air at 50 degrees F (both wet bulb and dry bulb), for an enthalpy of 22.
To achieve comfort and defogging, if we want to hit 69 degrees dry bulb and 50% relative humidity, that's an enthalpy of 27, delta of 5 btu/lb of air and a wet bulb of 58 degrees, smack dab in the middle of the winter comfort zone.

However, if we first cool the air from 50 to 40 degrees dry bulb, that's an enthalpy of 16, delta 6 (down from 22). Assigning a conservative performance coefficient of only 1.5 to the ac compressor brings our change in enthalpy down to 4 btu/lb. (Automotive HVAC COP from http://docs.lib.purdue.edu/cgi/viewcont ... text=iracc)
Then raise the dehumidified air to 69 degrees and it brings the enthalpy to 17 with a relative humidity of less than 10%. So the net change in enthalpy is 4+1=5 btu per pound of air for ac then heat, making very dry air that will dry the windshield quickly.

Moral of the story: moderate heating alone will suffice for defogging, but using the air conditioner will dry things out more quickly for no more energy.

At 98 cubic feet of interior volume, the iMiEV contains under 7.3 lbs of air, so a full turnover of the cabin would take 36.5 btu in the above example. On the bright side, we could "condition the cabin" 27 times for one kWh (excluding fan consumption and mechanical losses).

Using an ASHRAE average ventilation rate of 10 cfm per person, our little four-seater should get 40 cubic feet per minute of fresh air to keep the occupants fresh. i haven't found flow figures for our blower yet....
2012 i-SE "MR BEAN" 110,300 miles
2016 KIA SOUL EV, 90 kW, 27 kWh, 34k miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh

kiev
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Re: Solutions for windshield fogging in cold weather?

Thu Jan 21, 2016 2:43 pm

tigger19687 wrote:...
I do NOT have a remote for the car..


wonder if you can track down the previous owner and see if they have it sitting around.

or, go to ready mode with the ignition key while still plugged in/charging with the EVSE and turn on the defroster/heater--will this work similar to what the remote does?
----------------
edit: well i went and tried this and it doesn't seem to work--for one thing it won't go to ready mode, although it does go to 'ON' and the blower fan will operate, but i'm not sure that the water heater was actually heating. Need to do a longer duration test of this...
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jsantala
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Re: Solutions for windshield fogging in cold weather?

Fri Jan 22, 2016 12:25 am

No, it doesn't run the electric heater while charging, unless you have the remote to turn it on. With the french versions there is no remote, so we're stuck with no heat during charging. Unless one has a fuel heater installed, since it will still blow air thru the heat exchanger and the fuel heater has it's own water pump (at least mine does).

Sadly my fuel heater's fuel pump crapped out right now that we have toasty -25˚C mornings on end.
kWsaki.com / EVs: Nissan Leaf 2012, Citroën Xsara 1997 (conv. 81V & 8" Series DC) and Kawasaki GPX750R 1987 (conv. 87V & ME1003 PMDC) / Used to have a Citroën C-Zero 2011

Aerowhatt
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Re: Solutions for windshield fogging in cold weather?

Fri Jan 22, 2016 4:27 pm

jray3 wrote:Sorry to be flippant Aero. I spent Christmas skiing north of you in Durango. It felt like my parched amphibian skin would split open, but the chapped lips have finally healed.


One of my favorite haunts used to be Purgatory Ski area. Much more fitting name than it's current Durango Mountain moniker IMO.

I'm not a refrigeration engineer either. Just a Physics major (the science of engineering). I'm fairly certain that no one here cares about the humidity discussion in detailed scientific terms. They just want repeatable good results. Just a couple of points then my end of it rests.

1. The tables and graphs are apples and oranges compared with the systems working in our cars. Many factors, but just a couple for examples.

1. The AC coil in a vehicle is very small which leads to reintroduction of significant amounts of moisture to the airflow condensed on it as air recirculation continues.

2. Occupants add significant humidity to the mix breathing etc.

3. Refrigeration units suffer considerable stress when operating in a very cold environment (it's not what they are optimized for).

That said, something PV1 said got me wondering about how the system actually works. It does indeed have a damper that is actuated by the temperature selection. They thought it prudent to have the air flow bypass the heating coil when in the selector is in cool (down of the green dot). However in any mode the airflow still passes through the AC coil. So it's, filter first, then AC coil and then heating coil only if the selector is in heat mode.

With the heat on, one can use the AC to precondition the air before it gets heated. Mistu was pretty smart about how this whole system works. When making a selection all you are doing is telling the software what you want, or think you want. Then it decides what settings to actually implement to deliver the perceived desired result. I was able to find a couple of combinations that result in less than optimal adjustments by the software. But overall it is a very good and comprehensive system. Bottom line, if you simply can't get adequate results with defogging windows with the NON AC strategies, given previously by me and others, then just turn the dial to the defrost only mode. (Full right on the airflow selector) The system will turn on the AC in a limited way, for you.

Does it use more or less power to defrost with or without AC? That is a question that can only be answered for a specific set of conditions. Under most of them it will use more. There are also cases where it would use less. So do what works for you and get it off the full defrost setting as soon as conditions allow.

Canion fans can track all three usages, side by side, to see how things are working out AC/heater/summary(which of course includes all usage).

Interesting side note:
When you adjust the temperature controls in an ICE you adjust how much fresh cool outside air and how much is heated by the relatively stable temperature of the heater coil. Cooler settings more outside air less hot air and vice versa.

The 'i' controls the hot air temperature by controlling the water temperature (not by mixing hot and cold air). The very logistics of the system insures that an ICE will defog somewhat more easily than the 'i' will.

Aerowhatt
(July) 2014 cool silver ES, acquired new 4/2015 (40.9ah at ~34K miles)
(Aug) 2014 Labrador Black Pearl ES, acquired new 3/2016 (39.7ah at ~20k miles)

jray3
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Re: Solutions for windshield fogging in cold weather?

Fri Jan 22, 2016 5:34 pm

Aerowhatt wrote:.... how the system actually works. It does indeed have a damper that is actuated by the temperature selection. They thought it prudent to have the air flow bypass the heating coil when in the selector is in cool (down of the green dot). However in any mode the airflow still passes through the AC coil. So it's, filter first, then AC coil and then heating coil only if the selector is in heat mode. .....
The 'i' controls the hot air temperature by controlling the water temperature (not by mixing hot and cold air). The very logistics of the system insures that an ICE will defog somewhat more easily than the 'i' will.

Aerowhatt


Thanks A.- it's a good discovery that the system is routed and controlled differently than most ICE hvac, and that manual control could be counterproductive. My takeaway is to not fight the factory programming.

but... has anyone identified the main exit points for cabin air? I'm wondering if one could set it to exhaust from the floor in winter, and from a higher point in summer (other than driving with the windows cracked). Using natural stratification could help in both seasons.
2012 i-SE "MR BEAN" 110,300 miles
2016 KIA SOUL EV, 90 kW, 27 kWh, 34k miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh

PV1
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Re: Solutions for windshield fogging in cold weather?

Fri Jan 22, 2016 6:39 pm

The cabin vents are located underneath the taillights. Inside, these are behind the slots in the C pillars.

I guess I need to research our HVAC system some more.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015
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Aerowhatt
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Re: Solutions for windshield fogging in cold weather?

Fri Jan 22, 2016 7:23 pm

PV1 wrote:I guess I need to research our HVAC system some more.


Some things I observed seem a bit quirky. For instance when you have the fan running, temp on green dot, fresh air selected. Then you move the temp selector to cool. Of course the AC comes on but also the fresh air/recirculate "hood" (for lack of a better term) behind the glove box changes positions. Opening up part way to make part (perhaps as much as half) of the feed air into the blower to come from the cabin (partial recirculated).

Same thing happens if you have the flow set to any combination of floor and defrost. Temp in the heating position, set on fresh air and you manually push the AC button. This seems counter productive to me if windows are fogging already?

Aerowhatt
(July) 2014 cool silver ES, acquired new 4/2015 (40.9ah at ~34K miles)
(Aug) 2014 Labrador Black Pearl ES, acquired new 3/2016 (39.7ah at ~20k miles)

PV1
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Re: Solutions for windshield fogging in cold weather?

Fri Jan 22, 2016 7:43 pm

I've noticed that. It would be helpful to do the opposite, mix part fresh with mostly recirculated air.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015
"Photon" - 2017 Bolt EV LT in Orange with QC - 7/31/2017

Solar-powered since 10/10/2013

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