You might consider charging slower

[wraithnot]

Consider it verified. I set the charge timer to 10:00 PM and left it for two weeks on vacation. I have a sub-meter on my EV outlet. The car charged every other day to the tune of exactly 5 kWh starting at 10:00 PM. It did not draw power at any other time.

Now this was summer. I'll be doing the same in mid-December so I'll be watching to see how it fares in the colder weather.

If I'm parsing the battery diagnostic here correctly: Please Enter Access Code - Page 11
active cooling only kicks on when the battery hits 55C (a toasty 131F). Of course I don't know if this screen only applies to a moving car, a parked car on shore power, or at all times. And I don't really want to try and heat my garage to 55C to find out . . .

 

[djp]

If I'm parsing the battery diagnostic here correctly: Please Enter Access Code - Page 11
active cooling only kicks on when the battery hits 55C (a toasty 131F). Of course I don't know if this screen only applies to a moving car, a parked car on shore power, or at all times. And I don't really want to try and heat my garage to 55C to find out . . .

Yes, you're parsing that right, the Model S battery seems to operate about 10-15C hotter than the Roadster battery. This explains why the pack heater draws so much power in the winter (the 10C target is toasty in Canadian terms) and why active cooling rarely kicks in, except on a track. I had my Roadster at a track yesterday along with three P85s. The Roadster cooling system was a jet engine for most of the day while only one Model S had the HVAC spin up, and that was only for a few minutes after a professional driver did some exceptionally hot laps.

What is odd is 55C is extremely hot for standard Li-Ion NCA batteries. Either Tesla is using a very unique chemistry, or they've decided that the Roadster BMS settings were overkill and they can still get a decent life out of the battery while spending less energy on cooling (or a combination of both).

- - - Updated - - -

Thanks ZZB, I normally charge when needed. I plug in normally when I get down to 60 to 80, otherwise it is not plugged in. I still get confused with all the different options that this forum talks about. I hear that keeping the car at a high SOC all the time is not good, so does this not happen if you keep it plugged in and it charges everyday based on your charge schedule. If you do not drive the car, then it stays at the top end of the SOC.

There's a slider on the charging screen that lets you set the maximum %SOC level, so you can plug in every night and not stay at the top end of the SOC.

 

[SFOTurtle]

No need to worry. I ran 120v at 15 amps x 4 months until I got my 240v 50 amp NEMA 14-50 installed. I run the 14-50 at 5 amp x 240v when I only need 10 kW. Never had any problems with either setup.

Have you noticed any difference in the displayed rated miles one way or the other?

 

[brianman]

Update

Tonite (Monday) when I got home ...

I gave Tesla Service a call Tuesday morning and gave all the details I could remember, and requested that they pull whatever logs they can to research and get back to me with their thoughts.

What follows is a loose retelling from memory of a phone conversation so don't freak out if anything sounds troubling as it may be just poor memory or phrasing on my part....

• We had at least one brownout on Monday night, and that is likely to blame for the HPWC triggering a fault and telling the car about it. This is what stopped the charging.
• Either in reaction to the fault from the HPWC or for loosely related but not causal reasons, the vehicle registered a fault of its own.
• The vehicle's registration of a fault put the systems into a "protection mode" of sorts that halted trickle charging of the 12V, despite the main battery having plenty of charge available.
• In part because I don't have 5.0 yet, the normal vampire load accumulated enough that the 12V started reporting in as "below appropriate levels".
• Unplugging and replugging the cable (to trigger negotiation of a new charging session) seems to have bypassed the fault in the HPWC which woke up charging.
• The bump to (240V/)20A limit from (240V/)5A limit appears to have been an unnecessary step and not critical in getting everything "back on track".
• Tesla-fetched telemetry from the car suggests the 12V is fine. It didn't go into "troubled territory" as relatively quick observation of my telemetry logs and response with subsequent actions addressed the low 12V situation promptly.

TLDR: When there's a brownout, interesting things can happen with the HPWC and the car but so far nothing permanent/harmful has been identified in my case.

 

[wycolo]

Shouldn't you 'invest' in a plug-in voltmeter?
--

 

[djp]

TLDR: When there's a brownout, interesting things can happen with the HPWC and the car but so far nothing permanent/harmful has been identified in my case.

Interesting - that's a good argument AGAINST charging every night at low amperage, it increases the probability that you'll be hit with a brown out (or a voltage surge during a thunderstorm). If either are a risk in your area, you should consider charging once a week, and charging faster! :smile:

 

[montgom626]

Have you noticed any difference in the displayed rated miles one way or the other?

None.

Given how "crude" the dash is as a measuring instrument, that is to be expected. For example, if I see 197 miles one day and 199 miles the next, that is a 1% difference. As much as I love my P85, the 1% is within the margin of error for the dash gauges. Some folks see the gauges as precise, reproducible and highly accurate. Nothing could be farther from the truth. So, assume a +/-1% variability, 197 is the same as 195 to 199.

I hope I did not confuse anyone.

- - - Updated - - -

Interesting - that's a good argument AGAINST charging every night at low amperage, it increases the probability that you'll be hit with a brown out (or a voltage surge during a thunderstorm). If either are a risk in your area, you should consider charging once a week, and charging faster! :smile:

It is a reason not to get a HPWC.

 

[mknox]

This explains why the pack heater draws so much power in the winter (the 10C target is toasty in Canadian terms) and why active cooling rarely kicks in, except on a track.

What is odd is 55C is extremely hot for standard Li-Ion NCA batteries. Either Tesla is using a very unique chemistry, or they've decided that the Roadster BMS settings were overkill and they can still get a decent life out of the battery while spending less energy on cooling (or a combination of both).

Wow. 55C is quite warm and would explain why I never saw any battery conditioning draw from my outlet when I was away in July. The car would get nowhere near that hot in my garage unless the house was on fire.

I do see the pack heater on when driving and the weather falls below about 60 degrees F (based on the dash power gauge) but I've never seen it come on (based on my wall outlet meter) when the car is just parked and sitting. I'll be going away in mid-December for a few days, so we'll see if any battery heating draw is present. My guess is that I won't. I've read that Tesla lets the battery get pretty cold and only starts to warm it when the car is turned on or when you actively turn on cabin heat via the mobile app.

 

[AmpedRealtor]

The Model S battery seems to like higher temperatures. If you look at the range calculator over at Teslamotors.com, range is highest at 90 degrees ambient. As the temps go down, so does the range. Usually higher temperatures are a battery's enemy, so Tesla definitely has some unique chemistry.

 

[Dave EV]

The Model S battery seems to like higher temperatures. If you look at the range calculator over at Teslamotors.com, range is highest at 90 degrees ambient. As the temps go down, so does the range. Usually higher temperatures are a battery's enemy, so Tesla definitely has some unique chemistry.

All lithium batteries perform better (lower internal resistance, can handle more power) when hot - nothing specific to Tesla's. It allows electrons to "flow" more easily. That is why a cold lithium battery appears to have less capacity - more energy is lost to internal resistance.

The problem with high temperatures is that the battery degrades faster thanks to Arrhenius' equation. It seems that Tesla is confident enough in the durability of the cells that they don't feel the need to cool the pack much. It would be very interesting to see what operating parameters do trigger pack cooling.

 

[djp]

It would be very interesting to see what operating parameters do trigger pack cooling.

They're on the screenshot in the other thread. Passive cooling is triggered at 40C and active cooling at 55C. The pack heater target is 10C.

Agreed all Li-Ion batteries perform better but degrade faster in warm temperatures. The Roadster even has a Performance mode that pre-heats the battery, but the manual advises not to use it to often since it'll shorten the life of the battery.

 

[jerry33]

Bear in mind that range increases in hot weather because the air is less dense than it is in cold weather.

 

[montgom626]

Bear in mind that range increases in hot weather because the air is less dense than it is in cold weather.

What? Not a measurable increase by any mortal I know of.

 

[stopcrazypp]

What? Not a measurable increase by any mortal I know of.

The density of dry air at -13F(-25C) is 1.418 kg/m3 and at 90F(32C) is 1.153 kg/m3. This is a 23% difference.

The impact on drag is directly proportional, so I would say that is noticeable. The impact would be the same as if the Model S's Cd went from 0.24 (one of the best in the industry) to 0.29 (same as many decades old sedans).
http://en.wikipedia.org/wiki/Drag_(physics)

 

[David_Cary]

Air density is totally noticeable and measurable. Aerodynamic resistance is the vast majority of energy use at cruising.

 

[jerry33]

What? Not a measurable increase by any mortal I know of.

Just ask any pilot if it's easier to take off on a cold winter day or a warm summer day. The difference is very measurable.

 

[wycolo]

Air density - the joker here is water vapor. Makes computation complicated. High moisture content reduces air density since water vapor takes up more space than most other air components do. Florida actually a good place to view stars since it is generally warm & moist.
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[wycolo]

> I'll be watching to see how it fares in the colder weather. [mknox]

Cold morning: NO regen available - dotted orange line @1 o'clock (power limited). MS always plugged in so conclude: MS does NOT maintain min temp of battery yet. Maybe in a few months it will when it gets *really* cold.

New software finally nagged me: "Do you *really* want to keep slider @235?" So I reduced it to 200. Conclude: MS *now* prefers lower SOC. Noted.
--

 

[mknox]

Cold morning: NO regen available - dotted orange line @1 o'clock. MS always plugged in so conclude: MS does NOT maintain min temp of battery yet. Maybe in a few months.

I had limited regen last March when I got the car and we still had some cold weather, but never saw zero regen. The only time I had zero regen was right after a Range Charge, and it sure threw me for a loop when I let off the "gas", even though the power meter clearly showed it.

Now with the mobile app and "shore power" support, I'll be pre-conditioning the car in the morning once it gets cold, and I'm given to understand that when you turn on the heat, pack heating also starts. One thing I have to figure out is how far in advance of setting out should I turn on the heat.