Large Drop in Charge When Parked in the Cold

[dsm363]

This is the one thing that concerns me about the Model S. I will frequently use it to get to our cabin in the mountains, where there is no grid power. Only solar, which is too small to charge the S, and a Honda EU6500iS generator which I want to run as little as possible.

So here's hoping for a future "deep sleep/storage mode" software feature before I have to configure my car. I guess quite a few others also would like this fetaure.

It sounds like this isn't possible from what you wrote but are you able to trickle charge over that time period since you are there for so long to get a full standard charge with your solar system? (Similar to 110V outlet in US)

- - - Updated - - -

I changed the title to make it relevant to both plugged and unplugged in the cold situations since both seem to be a factor.

 

[jkirkebo]

It sounds like this isn't possible from what you wrote but are you able to trickle charge over that time period since you are there for so long to get a full standard charge with your solar system? (Similar to 110V outlet in US)

Nope. While the inverter surely would have no problems delivering for example 6A@230V to the Model S, the cabin batteries are not up to the task for any usable length of time. The array is only 900W and we do get very little sun in the winter. The battery bank has ~8kWh usable when full and is not always full when we get there. The 8kWh is not always enough even to run the cabin systems for the duration of our stay, hence the generator. If the battery bank get too low I can put 120A@12V into the battery bank from the generator (going through an Outback inverter).

In the summer we can stay mostly indefinately as daily solar production usually matches consumption, but there still aren't much left over to charge the car.

Now, if I had four of those 7000Ah LiFePO4 cells and a 5kW solar array on a dual-axis tracker I could do some useful charging

 

[montgom626]

It loses charge because of conditioning the battery when cold and keeping various electronics running. Apparently, once a charge is complete it will not "top off" until the State of Charge has dropped enough so that repeated charging will not reduce the life of the battery.

Thanks, the questions I now have are

1) At what SOC, while plugged in, does the MS have to drop to be charged?
2) When the charging resumes due to lowered SOC (see #1) how high does it take the SOC?

 

[MikeK]

I had a friend of mine pick mine up from the airport as I did not want to risk a stalled vehicle when I came back into town from vacation. He reported 143 ideal miles at the airport. When I left the vehicle 40 or so hours ago, it had a range of 217 miles.

70 miles in two days! :scared: I may be walking home...

I second @tezco's question: how cold was it?

 

[mdh]

This is the one thing that concerns me about the Model S. I will frequently use it to get to our cabin in the mountains, where there is no grid power. Only solar, which is too small to charge the S, and a Honda EU6500iS generator which I want to run as little as possible.

I will probably mostly arrive with 50-60% SOC remaining and might stay for up to 5 days in temperatures as low as -20degF in winter. I have taken the Leaf several times and it uses very little power in that scenario. If the battery gets down to -4degF or so it will use the 300W battery heater to heat it to around 7degF. At this temperature it is nearly impossible to charge the Leaf (charging power was down to ~500W at ~83% SOC) but driving was no problem at all. No regen for a while of course.

If the Model S attempts to keep the battery at an optimal driving temperature all the time I will have to run the generator a lot every day. That I seriously want to avoid. What I need the car to do is get to a "deep sleep" state where most electronics are powered off (I don't car if the screens take 2 minutes to boot up) and the battery temperature management only keeps the battery as warm as it needs to be to avoid damage. In the event that I suddenly have to drive the car I don't care if I have no regen and the power is limited to 50kW.

When I want to leave, after say 5 days, I'd ideally power up the generator for an hour or so, then waking up the car and letting it heat up the cabin and battery to optimum driving temperature (preferably with full regen as it is an hour of downhill driving first). The generator can deliver 24A@230V (5.5kW) continously which should be more than enough.

So here's hoping for a future "deep sleep/storage mode" software feature before I have to configure my car. I guess quite a few others also would like this fetaure.

I guess 4.0 SW sleep mode is not cutting it?

 

[wycolo]

> 70 miles in two days! [MikeK]

My guess is that maybe the cabin heater was left on, albeit at a low setting. Small button on center screen bottom turns this completely OFF. This should be clearer, maybe show an estimate of available hours at this setting (without draining batt too much??).
--

 

[MikeK]

Cabin heat shuts off when the car shuts off.

 

[pbrulott]

This thread is very interesting while concerning

It brings a fundamental question on EV: Outisde of the pure driving ecomonies (comparing wh/mi and mpge and ICE mpg), are we now saying that there is a signifiquant energy requirement 365 days a year to keep the pack warm and some functions alive? What is that cost?

And could I ask somebody that has a deep understanding of the matter (either plugged or unpugged with use case - really cold below -10F, cold 32F to -10F and avove 32F ) to summarize the issues and behavior encountered.

agree with jkirkebo, TMS needs a deep sleep mode and better cold management functions

PB

 

[JRP3]

Part of the problem is the batteries don't care if they get really cold, as long as they are not being used, but sub freezing temps can affect them during charge and discharge. So theoretically Tesla could disable any temperature conditioning while parked for long periods IF the pack could be warmed back up before use. Ideally you'd be able to put the car to sleep and have it wake up and warm the pack a few hours before you need to drive it. There is a risk that if you returned sooner than expected and the pack had not warmed enough the car would not drive to protect the pack.

 

[jomo25]

I'm still wondering how Cinergi is remotely monitoring.

And living in PHX, I'm more worried about the other end of the temp spectrum. What happens to the battery and SoC while sitting in ambient temps of 115 plus. Surface temps often can reach 150+ in the summer.

 

[Raven]

Add me to the long list....What temps?

My garage, although insulated, is not heated and is currently 33*F. External temps are currently a balmy -9*F with a high of +1*F. I'm concerned these batteries are far too cold blooded for me to use the car. I mean, will I need a 240v just to keep up with battery maintenance drain? I don't drive much so 120v is all I need. I planned from the beginning that I'd have to leave it plugged in to keep the pack warm, but if it's losing that much range a 120 will not keep up. Possibly the stated range is simply for a cold pack, not necessarily "lost range"? Warm the car through other means and watch range increase?

 

[wycolo]

Cabin heat shuts off when the car shuts off.

'Shuts off' = what? Do you mean locked? How do you know there is NO cabin heat or fan? My car is plugged in & charging. Maybe that is the difference. 117v 15A but how much is going to cabin heater?

So in the morning you could turn car ON with cabin set to 68 and after an hour it would be warmed up for your commute(?). Need an elf to hide in car after I lock it to supply hourly reports. :smile:
--

 

[dsm363]

Add me to the long list....What temps?

My garage, although insulated, is not heated and is currently 33*F. External temps are currently a balmy -9*F with a high of +1*F. I'm concerned these batteries are far too cold blooded for me to use the car. I mean, will I need a 240v just to keep up with battery maintenance drain? I don't drive much so 120v is all I need. I planned from the beginning that I'd have to leave it plugged in to keep the pack warm, but if it's losing that much range a 120 will not keep up. Possibly the stated range is simply for a cold pack, not necessarily "lost range"? Warm the car through other means and watch range increase?

I think you'll want a 240V anyway if that is possible. In such extreme climates, having the ability to draw more power would be helpful. Plus if you ever go on a big trip, the recharge time on a 120V with your pack is 60 hours. 120V is really only a limp-by kind of charging. It works but is very limited.

 

[Raven]

I think you'll want a 240V anyway if that is possible. In such extreme climates, having the ability to draw more power would be helpful. Plus if you ever go on a big trip, the recharge time on a 120V with your pack is 60 hours. 120V is really only a limp-by kind of charging. It works but is very limited.

My "commute" is 4 miles and that's only on days I decide to go in. 120 is more than adequate, unless 33* causes a dramatic draw that a 120 cannot keep pace with. Knowing temps and times would be helpful. Having guidance from Tesla would be even more helpful.

 

[dsm363]

My "commute" is 4 miles and that's only on days I decide to go in. 120 is more than adequate, unless 33* causes a dramatic draw that a 120 cannot keep pace with. Knowing temps and times would be helpful. Having guidance from Tesla would be even more helpful.

Nice commute. You'll probably be ok then but more information from Tesla would be helpful.

 

[highfalutintodd]

Sounds like Tesla either needs to open a couple of offices in MUCH colder climates than their Northern California HQ....... OR Elon and his family need to start taking some driving vacations to Alaska. ;-)

 

[montgom626]

'Shuts off' = what? Do you mean locked? How do you know there is NO cabin heat or fan? My car is plugged in & charging. Maybe that is the difference. 117v 15A but how much is going to cabin heater?

So in the morning you could turn car ON with cabin set to 68 and after an hour it would be warmed up for your commute(?). Need an elf to hide in car after I lock it to supply hourly reports. :smile:
--

I am waiting for my MS, so I can only tell you what I have learned driving a Volt 2012. On 120 v, if I preheat the cabin, the car preheats for 10 minutes, then stops the preheat (AKA remote start in Volt speak). Heating takes a lot of power. It takes another 20 minutes on 120 v to return to original SOC (full battery).

I assume the MS is no different. 120V is not enough to heat the cabin and keep up with the power drain from the battery required to do the heating at 120V 12 amp draw. NEMA 14-50 would probably be fine with the MS (just a wild guess) and heat the cabin without draining the battery. The 120V supplements/augments the power used by the battery to preheat the cabin.

 

[Larry Chanin]

It loses charge because of conditioning the battery when cold and keeping various electronics running. Apparently, once a charge is complete it will not "top off" until the State of Charge has dropped enough so that repeated charging will not reduce the life of the battery.

Thanks, the questions I now have are

1) At what SOC, while plugged in, does the MS have to drop to be charged?
2) When the charging resumes due to lowered SOC (see #1) how high does it take the SOC?

As I have stated earlier, I don't agree with Dennis' assessment that frequent topping off is avoided to preserve battery life.

Until someone camps out in their garage and actually monitors the topping off process, we won't have good information on item 1 (Ben's remote application probably will do the trick), but we do know the answer to item 2.

In Standard mode the car charges to 90% state of charge. In Range mode it charges to 100% state of charge.

Larry

 

[JRP3]

Depending on what heat level you set it at the heater could draw maybe 3-4kW while a 120V outlet can provide 1.5kW.

 

[djp]

Add me to the long list....What temps?

My garage, although insulated, is not heated and is currently 33*F. External temps are currently a balmy -9*F with a high of +1*F. I'm concerned these batteries are far too cold blooded for me to use the car. I mean, will I need a 240v just to keep up with battery maintenance drain? I don't drive much so 120v is all I need. I planned from the beginning that I'd have to leave it plugged in to keep the pack warm, but if it's losing that much range a 120 will not keep up. Possibly the stated range is simply for a cold pack, not necessarily "lost range"? Warm the car through other means and watch range increase?

I second the suggestion to go with a NEMA 14-50. Even discounting the heating load, charging at 120V is inefficient compared to 240V. Tom Saxton did a great comparison of charging the Roadster at different voltages and currents and found 120V/12A uses 55% more power than 240V/40A. Results are probably similar for the Model S.

Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog

Odd that I don't notice the Ideal Range changing on my Roadster as the battery temperature changes. I'm guessing it's a firmware issue with the Model S and not a loss of true range.