Extreme cold overnight hits Leaf Plus cold limits

[jjeff]

.....Battery temp.was interesting. I left with a high temp monitor reading of 51.5F, was at 52.5F at the halfway point, but was at 56.6F at the end (i did drive faster on way back), even at 12-15F outside temp battery warmed a little bit.

Thanks, I'll give it a try, it just seemed counterintuitive for energy savings to run both heat and A/C but your idea of being able to use recirc and in my case not bring in sub-zero temps may more than offset the A/C draw. Also I wonder if the A/C will even come on in my zero temps, sounds like you were in warmer temps....
I had a similar experience to you last weekend driving my '12 around when it was again around 0F. It started out with a battery temp of about 0F but quickly warmed up to 20F after only about 5 miles of mostly side streets with full heat, not full speed freeway driving. After less than 1 mile of driving I got the turtle, with I believe >60 SOC. It wasn't the full, crawl speed turtle you get with extremely low SOC but rather just limited me to 4? power bubbles(less than half) but was perfectly adequate to drive in. Note the turtle still stayed on my dash up to my halfway destination when the battery was 20F but after shopping for about an hour I started the Leaf, where I believe the battery was still around 20F and the turtle was no longer on. The power bubbles were still not full but just lacked the top 1/4 vs before when I only had the bottom 1/4 available.
I should note my '12 only has 8 battery bars so maybe that explains some of the odd behavior I'm having in extreme cold temps, looking at the histogram? of the battery cell voltages are all over the map

Need to dispel the ideology that AC will produce cold air somehow counteracting the heat. The A/C is only removing moisture and drier air is easier to heat up. I also found in milder temps, the AC on with vents closed helps to keep the windshield clear. The AC draws very little power with LEAF Spy registering power slightly less than half the time with the predominant draw being 50wh

Yes but how an AC removes humidity is by, passing the warm? air over a cold coil, you can't really dehumidify without cooling, that or just warming the air which would lower the relative humidity but not really remove any humidity. Now in the case of a car, I assume it first heats the air with the heater and then blows that warm humid air over a cold coil to dehumidify it. If the heat is more than the cooling you have heat, albeit cooler warm air than you'd have without introducing the cold coil, unless I'm missing something, which I could be? I believe that's why with a heat pump system you must use the resistive heater to dehumidify, AC to cool the coil and the resistive heater to heat it, you can't do both at the same time.

[DaveinOlyWA]

Ok, was out to get some free NCTC DC juice (what else is there to do anyway) and tried with the SV+. When just running heat, (6-8F) outside, both heater and heat pump ran (heat pump showing up as AC draw). When you click on AC, the heat pump stops, and it just goes to the resistive heater. With recirculation on, it did seem like lower power draw with both heat and AC on, but too short of a test to know for sure.

Thankfully the DC charger is in a garage, so it was a much more pleasant 32F. 30 minute charging session only added 15F (44 to 59F) to the battery temp. Interesting that post charging,temps went up an additional 1/2 degree before starting to slide on way home.

When I ran AC on the heat setting, it only pulses on so LS was giving me a power reading that varies from 50 to 150 wh but about 2/3rds of the readings were zero. The interesting thing is when I toggle heat off, the AC increases its power usage slightly but still near negligible levels.

[DaveinOlyWA]

Thanks, I'll give it a try, it just seemed counterintuitive for energy savings to run both heat and A/C but your idea of being able to use recirc and in my case not bring in sub-zero temps may more than offset the A/C draw. Also I wonder if the A/C will even come on in my zero temps, sounds like you were in warmer temps....
I had a similar experience to you last weekend driving my '12 around when it was again around 0F. It started out with a battery temp of about 0F but quickly warmed up to 20F after only about 5 miles of mostly side streets with full heat, not full speed freeway driving. After less than 1 mile of driving I got the turtle, with I believe >60 SOC. It wasn't the full, crawl speed turtle you get with extremely low SOC but rather just limited me to 4? power bubbles(less than half) but was perfectly adequate to drive in. Note the turtle still stayed on my dash up to my halfway destination when the battery was 20F but after shopping for about an hour I started the Leaf, where I believe the battery was still around 20F and the turtle was no longer on. The power bubbles were still not full but just lacked the top 1/4 vs before when I only had the bottom 1/4 available.
I should note my '12 only has 8 battery bars so maybe that explains some of the odd behavior I'm having in extreme cold temps, looking at the histogram? of the battery cell voltages are all over the map

Need to dispel the ideology that AC will produce cold air somehow counteracting the heat. The A/C is only removing moisture and drier air is easier to heat up. I also found in milder temps, the AC on with vents closed helps to keep the windshield clear. The AC draws very little power with LEAF Spy registering power slightly less than half the time with the predominant draw being 50wh

Yes but how an AC removes humidity is by, passing the warm? air over a cold coil, you can't really dehumidify without cooling, that or just warming the air which would lower the relative humidity but not really remove any humidity. Now in the case of a car, I assume it first heats the air with the heater and then blows that warm humid air over a cold coil to dehumidify it. If the heat is more than the cooling you have heat, albeit cooler warm air than you'd have without introducing the cold coil, unless I'm missing something, which I could be? I believe that's why with a heat pump system you must use the resistive heater to dehumidify, AC to cool the coil and the resistive heater to heat it, you can't do both at the same time.

Don't disagree with any of that but when using heat only, the power usage is higher than the combined usage of heat and AC together.

Now there is the issue of quantifying how warm the cabin becomes which is highly subjective but I can simply turn both on and eventually the heat will settle to 500 watts (depends on fan speed) and AC will bounce between zero and 150 watts (mostly zero)

Now the heat will bounce around occasionally but no real pattern I can discern. But I use heat only, it takes much longer to "settle" because it doesn't want to settle so i will see about 50% at 750 watts, maybe 10-15% at 500 watts and the rest at 1000 watts.

I tried this with thermostat set to 65 and 75 , both well over ambient to ensure AC does not enter "cooling" function and that appeared to make no difference at all.

I am sure I am missing something but I found this to be true last year and have done this at least half a dozen times with similar results.

[Kieran973]

Leftie, do you mean the -4F limit mentioned in the manual? So just don’t let the battery temp drop below that? How many bars on the temp gauge correspond to below -4? (And do the blue bars all the way to the left count?)

Sage, the reason I mentioned ambient temp is for a few reasons, one of which is the Li plating issue. My understanding is that charging the battery at any voltage - L1, L2, or L3 - when the battery temp is below 32F can lead to this, yes? But then what do you do when it’s in the mid 20’s F for weeks at a time, your daily commute isn’t enough to really warm the battery (only 6 miles each way, with an 8 hour break in between where the car sits outside in a parking lot), and you tend to both park it and charge it outside all winter? In the summer, when your battery gets too hot, you can just wait for it to cool down before charging it. But in the winter, unless the plan is to just wait for spring, you can’t really do that. I usually tend to park my Leaf outside in the winter because my L2 EVSE (12 amps, 240 volts) is on the outside of the detached garage, though I could park it inside the garage if necessary and trickle charge on a 120 outlet. The garage has very little insulation so I’m not sure how much it would even help (this is the reason the EVSE is not inside the garage - because it gets extremely hot in there in the summer). Lately, I’ve been doing the same thing you do - charging it immediately after driving it, because the battery is warmer then. But the other reason I asked about ambient temp is for a sort of lazy, general rule of thumb, that way I don’t have to take a Leaf Spy reading every time I make a decision about where to park the car. (Like in warm weather, when ambient temp is above 60F, I try to avoid parking the car in the sun).

So I guess what I’m really asking is: should I just be parking the Leaf in the garage all winter? Or is there a conveniently measurable cutoff ambient temp below which I should park in the garage? By ‘conveniently measurable’ I mean just knowing/checking the ambient temp, or looking at the battery temp gauge in the Leaf real quick, as opposed to going inside and getting the OBD dongle and kindle (because I don’t store those in the car, in order to protect them from extreme temps as well), coming back outside, and then taking a LeafSpy reading, every single day.

I guess one way to minimize plating would be to do fewer charging sessions overall and just charge to a higher than normal SOC each time, but then you have to weigh the benefits of that against the problem of then letting the car sit at a higher SOC. In the spring, summer, and fall, I try to almost always keep the Leaf at or below 60% SOC. I guess I could charge to 80% during the winter if that would reduce the total number of charging sessions, but I’m not sure whether that would be better.

[LeftieBiker]

Don't disagree with any of that but when using heat only, the power usage is higher than the combined usage of heat and AC together.

This has come up before. It is almost certainly a mistake in programming the energy monitor. The car likely doesn't actually monitor energy use directly, but instead it probably uses some sort of lookup table, and when it looks up "Heat + A/C" someone left the PTC power draw value at or near zero, causing it to ignore the amount of energy used by the heater. This is only a theory, but it should be testable.

Leftie, do you mean the -4F limit mentioned in the manual? So just don’t let the battery temp drop below that? How many bars on the temp gauge correspond to below -4? (And do the blue bars all the way to the left count?)

Yes, I mean the lower limit mentioned in the manual. Remember, this refers to battery temperature, NOT air temperature, because the battery is usually significantly warmer than the air on Frigid Winter nights, due to its large thermal mass which resist rapid temperature changes. I suggest using LeafSpy Pro to watch the battery's internal temperature sensors. I've seen zero temp bars before, so -4F is below the point at which that "gauge" stops giving a reading.

[DaveinOlyWA]

All good questions and I think the easiest way is charge every day. I normally charge 24 amp 5.88 kw for 1 hour 20 mins daily during my 4 day commute and 2 hours+ on my 3 days off. This keeps the pack from getting super cold but I am not sure that 120 volt charging is enough to keep a pack from freezing? I did 3 hours the other day and my pack temps only went up 4º and that was in a garage at 50º Surprisingly, the pack was hovering at 46º so colder than I was expecting. I had only done a short (but arduous ) 2 mile RT on 8 inches of fresh snow the day before so it did have over 18 hours of sitting time by the time I started the charge but no work commute so no extended time outside the garage.

Apparently the far left dash light flashes when battery warmer is working (the same one that indicates 12 volt battery is being charged. With 3 lights, it would seem they could have made different signals...) so if anyone was lucky enough to catch that and can throw LEAF Spy on it to see if there is anything in the logs that would show it?

[LeftieBiker]

Can someone repost the relevant excerpt from the Leaf owner's manuals for the 40kwh and 62kwh cars? FWIW, people have fitted oil pan heaters to the Leaf's battery pack, in 2011 cars with no warmer. This would probably be a good idea for those cars that reside in really Frigid Winter climates but don't have battery warmers. The oil pan heaters stick on and run on house current, but it wouldn't be too hard to give them AC power from an inverter and a storage battery - either a second 12 volt battery or a much higher capacity battery replacement for the OEM accessory battery. The trick would be to set them so that they keep the traction battery from freezing but don't drain that storage battery...

[SageBrush]

I guess one way to minimize plating would be to do fewer charging sessions overall and just charge to a higher than normal SOC each time

YES
Don't worry about a high-ish SoC in the winter

COLD winter, short drives -- That is a tough combination to avoid low battery temps that lead to battery plating during charging. You will have to waste some battery energy to bring battery temp up into the 30s or 40s F for non-destructive L2 charging. In your shoes I would have the heater on full blast during the drive before the charge, and if needed I would continue to run the heater while parked until the battery was out of the cold danger zone. You can also think about pre-heating the car before the drive

Some numbers:
Tesla has said that the specific heat capacity of the 80 kWh Model 3 pack is 85 Wh/Kg*C
If you figure the LEAF is similar per kWh, then ~ 1 Wh/kWh*C new capacity

If your car has resistance heating elements in the pack then it is not that much energy to heat up the pack
Without them, you are relying on pack inefficiency losses which are I*I*R

----
I mentioned above that my Tesla heats up the battery to somewhere in the range of high 30s F before L2 charging. The couple of times I spent enough time watching the process, it took about 10-15 minutes of 6 kW to raise the pack ~ 10F. That is more energy than the above calc would suggest but my car ends up heating with a COP < 1 because it runs the motor inefficiently and then scavenges the heat into the coolant fluid which is then dumped into the battery. One of the upsides of this approach is being able to use shore power for the task.

[Kieran973]

Thanks, all.

I just took a Leaf Spy reading because I was curious about the difference between battery temp and ambient temp in my garage. The car has been sitting in the garage for about two days. Ambient temps have been in the 20s and 30s F. When I took the Leaf Spy reading, my phone said that the outdoor temp was 37 F. The instrument panel in the Leaf said that the temp in the garage was 35 F. Leaf Spy said that the outside temp (temp in the garage) was 35.6F, and that the battery was 34.2 F max (there is also the thermometer image on the next page which said 33.85 F). So a couple things. One, the battery does seem to be weirdly just below the ambient temp (I'm not sure why). And two, the garage is so poorly insulated (there are some gaps along the rim joists where the roof meets the walls) that it seems to be roughly the same temperature inside as outside (so no point in parking in there, other than to keep snow off the car).

The other unpleasant thing I discovered with this Leaf Spy reading was that my car seems to have lost about 3% SOH in the last three months. Ouch. Not sure why. I've kept the car between 40-60%. I don't think I've done much L2 charging in sub-freezing temps. I fast charge once a month at a nearby EVGo station, though I only add around 2 kWh (3 minutes and then I unplug) - I don't do this for the free electricity but to remain eligible for the Smart Charge program which provides monthly cash incentives plus useful info about driving efficiency. But more on that SOH drop in the proper battery thread.

Dave, I think the charging every day strategy is a good idea, but it would depend on how cold it gets here. If outside temps are in the twenties, then I don't want to charge every day. But if they're in the high thirties or so, then charging just a little bit every day might give me the boost to keep the battery temp above freezing.

Sage, I will try charging to a higher SOC in the winter from now on (probably 80%), and also running the heater full blast before hand as necessary. But for this to truly reduce the number of charging events I would also have to do a deeper discharge. So what's better? Cycling between 40-60% SOC but charging when it's in the twenties fahrenheit outside? Or cycling between 20-80% but never charging when the battery is below 32F?

[DaveinOlyWA]

Thanks, all.

I just took a Leaf Spy reading because I was curious about the difference between battery temp and ambient temp in my garage. The car has been sitting in the garage for about two days. Ambient temps have been in the 20s and 30s F. When I took the Leaf Spy reading, my phone said that the outdoor temp was 37 F. The instrument panel in the Leaf said that the temp in the garage was 35 F. Leaf Spy said that the outside temp (temp in the garage) was 35.6F, and that the battery was 34.2 F max (there is also the thermometer image on the next page which said 33.85 F). So a couple things. One, the battery does seem to be weirdly just below the ambient temp (I'm not sure why). And two, the garage is so poorly insulated (there are some gaps along the rim joists where the roof meets the walls) that it seems to be roughly the same temperature inside as outside (so no point in parking in there, other than to keep snow off the car).

The other unpleasant thing I discovered with this Leaf Spy reading was that my car seems to have lost about 3% SOH in the last three months. Ouch. Not sure why. I've kept the car between 40-60%. I don't think I've done much L2 charging in sub-freezing temps. I fast charge once a month at a nearby EVGo station, though I only add around 2 kWh (3 minutes and then I unplug) - I don't do this for the free electricity but to remain eligible for the Smart Charge program which provides monthly cash incentives plus useful info about driving efficiency. But more on that SOH drop in the proper battery thread.

Dave, I think the charging every day strategy is a good idea, but it would depend on how cold it gets here. If outside temps are in the twenties, then I don't want to charge every day. But if they're in the high thirties or so, then charging just a little bit every day might give me the boost to keep the battery temp above freezing.

Sage, I will try charging to a higher SOC in the winter from now on (probably 80%), and also running the heater full blast before hand as necessary. But for this to truly reduce the number of charging events I would also have to do a deeper discharge. So what's better? Cycling between 40-60% SOC but charging when it's in the twenties fahrenheit outside? Or cycling between 20-80% but never charging when the battery is below 32F?

On the SOH drop; that is how nearly every Gen 2 LEAF has done. You lose the first 7-10% within 18 months or so then the rate drops way down. I know one LEAFer who was at 91% after 15ish months on his 2018 @ 25,000 miles. He is now at 57,000 miles and at 88% so a dramatic difference. He just past his 3 year anniversary a few weeks ago.

Still looking for the first Gen 2 to have dropped a capacity bar.

As far as the temp thing? Mine was below what I had suspected was the low temp in garage at 48º (garage was only 51º) and car had been in garage over 18 hours but when driving every day just 14 miles one way 11 hours apart, I was able to keep the batteries in the mid to upper 50's. So even a little bit helps.

I guess what I am really trying to say is don't do what a lot of people seem to do and charge only once or twice a week. Right now its easy for me to charge every day because my needs are pretty light right now. It will be more interesting come Summer when road trip season starts back up.