range/efficiency maximization with heater

[defiancecp]

So I've got a variable daily drive that goes from 20 to 40 miles total per day. 10 miles to work, 10 miles back, sometimes I meet my wife for lunch at a variety of locations up to 7 miles from work, and I often pick up the kid after school which adds 5 miles to the return trip. Great drive for the leaf! I always charge to 80% since more isn't necessary.

So thinking of the worst-case 40-mile day (which is pretty common)- Normally I get home with just a touch under 40% (based on the bars-to-percentage estimates here in the forums). The few times I've pushed it further, I've gotten right at 60 miles on 80% charge, which is dead-on consistent with the above numbers, I think. Dash efficiency shows 4.2-4.3 mi/kwh every day (3.9-4.0 when I get to work for whatever reason, maybe slightly higher elevation, whatever). All that works very well.

I freely use A/C and it makes minimal if any difference - I manually control it, turn the temp all the way down, set it to recirc, and turn the fan all the way down once the cab is a nice temp. Normally this drops the climate control down to a negligible sliver on the console display, even on very hot days.


This week is the first time I've had a major cold shift since having the car. The first day I used it, I turned on the heater, recirc, all the way up. It was about 40* outside. I normally don't bother with pre-cool or pre-heat, so I just didn't think to do it at all. About 2-3 minutes into the drive, I saw how horrible I was doing efficiency-wise, and noticed the heater was showing 4.5 kw draw (CRAP), as I was defrosting at the time with temp all the way up. I figured my daily numbers were shot, and decided, I wonder what the REAL worst-case scenario is? I didn't need to meet my wife for lunch that day, so max of 25 miles needed...... Let's just see how bad I can make it go. I turned around and went to the interstate, put it in D, braked at the last minute for every stop light and gunned it coming out of them, floored it until I hit 70 on the interstate, cruise controlled up the hills, kept the heat cranked the whole time, etc.etc.etc. I ended up with an efficiency of 2.8 at the end of the day, and doing the math put me at about 37 miles range on the full 80%.

Now I know this is all worst case, and I can do a ***LOT*** better, so it doesn't concern me. Yet....

The next day (yesterday) I decide to see how *good* I can make the efficiency with heat on. I start off pre-heating before I leave, put it in eco, I drive smooth, take the city streets, drive same speeds and easy accel as I do on my normal (4.3, 60mi/80%) days.

For heater operation I fiddled with it a bit - Looks like with heat/defrost on, temp at max, recirc, it starts at around 4.5 kw and eventually drops - but only to about 3 kw. Turning off defrost cuts it back to just over 3 starting, about 2 maintaining. And finally, setting the temp where you actually want it drops the maintaining usage to 1-1.5 range, but looks like that's about as low as it gets, as far as I can tell. So, that's what I've been using; preheat, then keep temp set to 74, recirc, fan low. Push defrost button when the windows fog, and turn it back off as soon as it's clear - which takes about 15-30 seconds, and I'm probably doing it 3-4 times on my 10-minute trip. So my guess would be I'm averaging 1.8kw heater usage, and I can't see a way to get lower.

But even with that, I'm still seeing a huge impact. On the second day, I got to work with the dash showing 3.0 - a full 25% less than I normally get. When I got home, it showed 3.3, so again almost 25% down. I'd like to have validated that impact with a range/battery estimate, but it was wrong; when I pre-heated the car, I went out to get in and it had charged up to 11 bars...

BUT - when I do 40 miles in a day, normally that gets me back with 2 bars (a few miles after dropping to 2 bars, though) Assuming there's about 14% below 0, bar 1 is another 7%, and bar 2 is 3-5, that's around 24-26%-ish remaining, 54-56% used. Even starting at 11 bars, I had just dropped to 1 bar when I got home yesterday. If I only count it as 92% charged (I think 11 bars is above that), that's 71% used for 40 miles, giving me a BEST CASE 80% range of 45 miles, 56 miles at full charge... Again, dead on 25% drop, though the math is fuzzier.

This morning I tried taking it easy again, was up to 11 bars when I got to the car again, and I'm showing 3.0 when I got to work. So it looks like this is a real drop...

I thought I was done with range anxiety after the first week - but now that I'm doing the math, I realize that for the first time, getting all the driving I need off an 80% charge is barely possible - and if this gets worse as it gets colder, that becomes even more of an issue. It's somewhat less of a problem since I get extra charge from pre-heating, but still; that for the first time gives me something to worry about if the battery does degrade any over time...




My first question for anyone with cold weather experience is, is there an 'efficient' way to run the heater? I feel like the A/C can be operated EXTREMELY efficiently, but the way to do it was a bit tough to figure out. Is there something like that with the heater?

Second, are you guys seeing a similarly dramatic drop in efficiency with heater use? I guess it's actually a combination of the cold and the heater; loss of efficiency plus increased drain. I just didn't expect quite so much!

I guess the good news is this is unseasonably cold. We're a bit colder than, for example, portland - we see on average about 50 days a year where the low is sub-freezing (compared to portland's 40). So hitting low 40's in October is pretty unusual.

 

[camasleaf]

When I noticed that the car heater takes about 2kW and few minutes to warm up the car, I did a test where I put in the car a 120V ceramic heater (powered from the outlet). Within 1 minute, on the low setting (~800W), the heat in the car was more than enough for me. So, I would say the Nissan way of heating the car is kind of inefficient. When I first heard that it heats a liquid first, I believed the reason was to store a lot of heat in the liquid while plugged in. It does not seem to work that way.

The few mornings that we were bellow 50 here in Portland area, preheating the car (in the garage) worked fine for my wife. She did not need to turn the heat on for the 25 mile round trip to school.

If we need the range, I guess we will have to put more clothes on ....


As a side note, for defogging the windows, I put the car on defrost than turn off the climate control and push the recirculation button. When it starts to get foggy, I just push the Climate Control on. Like you said, it only takes 20 seconds to clear up, than I switch climate control to off. If is only one button operation and it seems to work well in the rainy weather here in Portland (as long as you clothes are not soaking wet).

 

[smkettner]

Not at all cold here yet but you said twice you put temp at max. Why not try 68-72 and leave it to auto and see how it goes.
A warm drink on the ride might help.

Then turn the heat off the last couple miles.

 

[defiancecp]

I put it on max because of my experience with the AC, if you set the AC to a mid-level temp it draws a bunch more power than it does with the minimum temp. As I said above, the second day I tried it with the temp at 74 and still had huge range/efficiency losses (~25%).


Hm... so I wonder... It occured to me that I might just keep the heat off and turn it on in short spurts as needed... But I don't think that would help would it? Since it has to heat the fluid, it would take so much juice re-heating that it would undo any savings you might have had... wouldn't it? Or maybe not, I dunno... Something to try anyway.

Preheating then turning it off in the mornings is definitely an option I'll be using, but there will still be some significant loss doing that at lunch and on the way home.


It just shocked me just how much juice that thing sucks up... I mean all the above options are doable, sure - but this is the kind of crap the anti-ev crowd LOVES to hear, you know?

 

[kmp647]

My recent cool rainy drive in the leaf I used the eco setting and noticed reduced consumption by the heater/a/c

Dont see if you were trying ECO or not but it promises to tame hvac consumption and you can see its effect by switching in and out od eco while the heat is on and the energy screen is showing CC usage.

forget all this flipping switches unless absolutely necessary

set ECO mode for reduced climate
set auto at a reasonable temp and drive

make a change just to shut off system if you are low on range

 

[defiancecp]

It was in eco the entire time, other than the "worst case" run I made just to see what would happen. Still chewed through the juice like a swarm of half-starved piranha (25% reduced mi/kwh)

 

[kolmstead]

defiancecp, my drive is similar to yours, but I got the LEAF in January, so I've seen more cold; many 24 to 28 degree mornings. I averaged about 3.2 mi/kwh last winter; 4.9 mi/kwh this summer. 34-50 miles/day, 80% charge. Run the heater temp and fan as low as you can. This morning, about 50 degrees, I preheated and then left CC set to 60 degrees. I didn't see any heater power draw until I was about fifteen miles into the trip. Last winter I ran temp at about 65 and was comfortable. Since humidity is low here, I run outside air instead of recirc. I don't use Auto CC setting much. It turns on A/C too much to suit me.

As smkettner stated, don't assume summer rules still apply! Oh, and running the temp up too high defeats the ECO setting. ECO limits heater to about 3 kW, but if you run it up to 90, you'll see 5 kW draw.

-Karl

 

[tech01]

We are in Chicago. Winters are a little more challenging. does anyone have experience with temps hovering in the 0 degree range. Preheating seems to be derigeur. Does the conventional battery (group size 45) get involved; ie. powering the fan. does having the radio cranked reduce range? Heater on with the headlights on, we have reduced daylight in the winter here. Many of our excusions are after sunset. :roll:

 

[dgpcolorado]

I'm thinking about trying this suggestion by Herm:

...How come no Leaf owner ever talks about using electrically heated vest and gloves?.. very common in the motorcycle world. Its not a lot of power, 200watts in a vest would roast you.. and its instant heat.

sounds like a good idea - any links and what is the power source?

They run on 12V, but make sure you get one that is adjustable or you will roast. Do a search using "heated motorcycle vest" in Amazon.com

 

[defiancecp]

Ok, It's still going to be low 40's again tomorrow, so I'll give it a try preheated and down to 65, then just 65 in the afternoon only if needed. Hopefully that'll cut it way down. Still, with your winter average dropping from 4.9 to 3.2, it sounds like I'm probably already in the realm of 'about as good as it gets'.

Hm... I wonder if it might make sense to switch to slow interstate driving - it's about the same distance, but cuts the time down from 30 minutes one way to about 20. I wonder if the increased efficiency from having to run the heater for a shorter time might make up for the loss from additional speed...

Think I'll try that on the way home today.

No way I'm completely doing without or getting motorcycle vest/gloves - especially not on days when I pick up the kid

Besides, I've given my coworkers a great impression of the leaf so far; what would it do to that if I'm putting on heated gloves & jacket as I leave, and when they ask why, I say, "Oh, it's so I can avoid running the heater in my leaf." :lol:

I just need to reset my expectations I guess. Not at all enough to make my drive trouble, though it does look like I'm going to possibly rely on that 11th bar I'm getting in the mornings if it gets really cold. And in the long term, if I lose a bit of capacity I'll just have to start 100% charging in winter.

 

[abasile]

Heater on with the headlights on, we have reduced daylight in the winter here. Many of our excusions are after sunset. :roll:

The headlights are LEDs and barely use any power, so I wouldn't even worry about that. I sometimes use the headlights during daylight hours when I feel extra visibility is needed.

We hardly use the car's heater when the temperature is in the 40s, unless perhaps my wife has just consumed a couple of glasses of iced tea! Even if the outside temperature is in the 20s or 30s, not that much heat should really be needed if you keep your winter hat and jacket on. Let's face it, keeping you toasty warm is not one of the selling points of a 24 kWh EV, unless you're only driving short distances.

 

[padamson1]

I am getting my new LEAF with the Cold Weather Package (CWP) in a week or two. I will be very interested to see if Nissan has made any alterations to the climate control system to shift the heating load from the cabin climate control to the seat heaters.

Seat heaters typically draw 30W per seat so they obviously a much better way to keep warm. But if the lowest climate control setting is 60deg, the inefficient cabin heater will still be on for a significant period if you want to circulate air to keep the window clear.

Sounds like the most efficient method may be seat heaters with a portable defroster plugged into the 12v outlet.

 

[defiancecp]

We hardly use the car's heater when the temperature is in the 40s, unless perhaps my wife has just consumed a couple of glasses of iced tea! Even if the outside temperature is in the 20s or 30s, not that much heat should really be needed if you keep your winter hat and jacket on. Let's face it, keeping you toasty warm is not one of the selling points of a 24 kWh EV, unless you're only driving short distances.

Let's be honest here, the usage pattern you've described (not using heat in the 40's, minimal heating below that) is a significant disadvantage in comparison to a traditional ICE. Perhaps not to you, but to me and to probably 90% of drivers. This car is meant to be a foray into the mainstream for EV's, and I, like many of the members of this forum, are pretty regularly explaining to people how practical it is. "Just don't use the heater in the 40's" is completely incompatible with that position for most people.

 

[smkettner]

Save what you can but I see nothing wrong with going 100% charge and not stress too much over it.

 

[abasile]

Let's be honest here, the usage pattern you've described (not using heat in the 40's, minimal heating below that) is a significant disadvantage in comparison to a traditional ICE. Perhaps not to you, but to me and to probably 90% of drivers. This car is meant to be a foray into the mainstream for EV's, and I, like many of the members of this forum, are pretty regularly explaining to people how practical it is. "Just don't use the heater in the 40's" is completely incompatible with that position for most people.

While you have a valid point, I think it's best to be upfront about the car's limitations. Blast the heat all you want if you're not going far, but if you want to maximize range and/or efficiency, then bundle up and/or use heated seats. You're right that this doesn't bother me, as my wife and I tend to prefer cooler temperatures anyway.

 

[nosuchthing]

Why are you worrying about the battery? What's with this wimpy 80% nonsense? It's made to take the 100% charge, it's guaranteed for 8 years/100,000 and bottomline? You'll be replacing it anyway in about 5 years not because it's dead, but because by then the Toyota 1000 km battery -- or a similar breakthrough product -- will be out and available for purchase for 2-4 grand. I'd to it today if it was available. There are billions fed into the batt research as we speak. This first gen battery is going to be history before you know it.

I pump that sucker with electrones whenever I have a chance, so it's always 100%. Period. Leaf needs more kilowatts -- badly. I'm at 9000 miles and have been in turtle mode twice. No fun there. You sweat it.

Charge 'er up! Run the heater as you please.

 

[defiancecp]

Why worry? I'm a chronic early adopter. I love new stuff! And that's no small part of my passion for the leaf. But as a chronic early adopter, I've had my fair share of stuff with first-gen flaws. And some of those flaws reared their ugly heads well after the first year of ownership... So I just want to be sure that I can honestly and openly say to the dealer in 2 years or something, "Look, I treated this thing NICE. 80% charge almost every time it was used, just because Nissan said it would be better for the battery." That kind of thing. Sure, I think there's a very small chance that'll ever come up, but if it does, I want to be able to say that. Having said that, if I have to charge to 100% a few days a year, so be it

Abasile, you're right of course. I'm just a little disappointed that Nissan didn't configure the heater a bit better than this - Seems like this is the kind of thing that would scare the crap out of anyone that bought it in the winter I remember when I was a leaf-noob, my first few drives were pretty nerve-wracking, watching the miles remaining guess-o-meter plummet... I can't imagine if it would've been combined with this!

 

[smkettner]

No reference but I think 100% once a week or so is good for the battery.

 

[lonndoggie]

You might want to consider something like this 12v car seat cushion (a DIY version of the cold weather package):

http://www.overstock.com/Home-Garden/Heated-12-volt-Seat-Cushion/5267218/product.html?rcmndsrc=2" onclick="window.open(this.href);return false;

There are also heated car blankets and pads. The blanket idea sounds a bit sketchy for the driver, but one example I was looking at showed the driver covered, so I suppose it's not so bad.

We were in Kenya a couple of years ago, and we'd go out on safari trips in the morning in open Range Rovers, some of which we had a bit of a drive at not-quite highway speed, enough to make it very cold, what with the wind and early morning cool. We'd throw a wool blanket over our laps and the situation would improve dramatically.

 

[Herm]

I doubt it will make much of a difference but Nissan does keep track of how you charge the battery, its part of the yearly battery checkup and report that they give you.. so perhaps if there are issues and you have babied the battery they will voluntarily take care of it.. its good publicity for them.

GM does not give you the option to abuse their battery.. they restrict how it will be charged and discharged very strictly, and thus can afford to give you a range warranty of 40 miles even at 10 years (8 years in non-CARB states). Nissan does not give you a range warranty.