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Battery Warming

Battery Warming

I know that the battery has to be warm to get good rates of charge from a SC and also to allow good regeneration. But what is the optimal way to warm your battery in cold weather (<32 degrees) ? Also when the battery is cold does this affect projected range and if so will this improve as the battery warms up? Lastly, will the battery warm up just by driving ? Thanks for opinions and experience (looking at you @Bighorn) !!!

jimglas | November 15, 2019

I charge for 15 minutes before I leave in the morning, seems to work for me.
Yes, the battery will warm up by driving.

jordanrichard | November 15, 2019

I gather you didn’t do any research before getting your car...........

When traveling, if and only if you have a SC set as a destination, if your battery needs conditioning for charging, the BMS will do it automatically.

If you are talking about what would be best first thing in the morning, that would involve having your charging complete just before you leave for the day.

Yes, the battery will warm up while driving. What heats up the battery is electrons going in and out of the battery. IF the battery is cold, your regen will be limited because the battery can’t handle full re-gen when it’s cold.

Bighorn | November 15, 2019

Most efficient way is to end your battery charging right before your departure. Using the climate app to heat the cabin will also turn on the battery heater if the battery is about 40 degrees or colder. Programming a supercharger into nav turns on battery preconditioning in my Model 3, but no sign of it in my Model S. Model 3 does not have a dedicated battery heater and uses a novel heating of the motor stator, which is a permanent magnet motor feature I believe. If any Model S have the feature, I suggest Raven is the dividing line. A cold battery will show a snowflake with a small portion of the battery showing as inaccessible, but that energy is regained upon warming. Current flowing into or out of the battery serves to heat it, so acceleration/maintaining speed, regen and charging all contribute to battery warming.

marcustcohn | November 16, 2019

Thanks for the responses - although this is Model S number 5 all my long distance experience has been in the summer so this is my research.

So topping off at the nearest SC in the AM while heating the cabin and setting a destination to the next SC would help warm up the battery and then driving should take care of the rest - did I miss anything ?

jordanrichard | November 16, 2019

BH, for quite a long time, I do get the battery heating symbol on my app when preheating the car. I don’t as you said, get it in my MS (2014) and just assumed it was doing it behind the scenes. I really don’t under why it wouldn’t be on all cars since it doesn’t require any physical equipment be added. For example, my car doesn’t have AP and no software update will change that because there are physical components that differentiate my car from a AP car. For this pre-heating of the battery on route to a SC, there isn’t, to my knowledge, any additional components. My car has the ability to pre-heat the battery when it’s needed. When using the nav, it knows where I am going, so to connect the two, unless I am missing something, it’s merely a communication issue via software, between the nav and the battery heater.

Bighorn | November 16, 2019

@jr
My 2013 Model S shows a battery heating icon on the app about a minute after I turn on climate remotely. It simply activates based on temperature. The Model 3 has a different approach including heating en route to a supercharger. Different system and the nav is not a prerequisite for heating on the S.

@marcus
One caveat about heating up the SC in the morning. If the car is cold, it won't supercharge and it takes a long time for the battery to heat up in order to do so. Better to have your outlet do the morning charge when you don't have to sit and watch it happen. Being in a garage is your best friend because a frozen battery is a real hindrance. Setting a destination won't help in the S as I pointed out to @jordan above. The Model S battery heat comes on regardless of destination. It's a 6 kW draw that will turn on unless you're in Range mode, which inactivates it. It also comes on with the climate app via phone. When I tried to SC at 0 degrees, it only drew 1 kW from the supercharger, so I don't even know if the battery can tolerate the full 6 kW of normal battery heating. I think the longest I've heard of the heating delay is 71 minutes--I waited about an hour for my juice to start flowing.

marcustcohn | November 16, 2019

@BH - It is on the road I am concerned about - like to be off and running really early in spite of the later sunrise but want to get the cabin at a tolerable temperature. If I plug into a SC station will that allow heating without draining the battery and hopefully (slowly) warm it up enough to charge ?

marcustcohn | November 16, 2019

@BH - Or would it be better to charge at the end of the day and then just drive and let the battery warm by driving and accept the shorter range so that when I arrive at the next SC the battery will be warm ?

Bighorn | November 16, 2019

Definitely charge at the end of the day and preheat the cabin in the morning using the app. That will also warm the battery some, though will use a few percent of the charge. Charge accordingly. Driving will continue to warm the battery. It can take 50 plus miles of driving to fully warm the battery, but it's kind of moot to subsequent supercharges that day.

jpcollins9 | November 17, 2019

Am having an issue with my 12 volt battery in my 2015 S85D. For the first time in 4 1/2 years, the warning light indicates there's a problem and the 12 volt battery needs replacing. mobile service has scheduled me 2 weeks from today. Should I be concerned about driving over the next two weeks?

Bighorn | November 17, 2019

@jp
Most people have no issue in waiting weeks to months. Is the light coming on consistently?

TeslaTap.com | November 17, 2019

Here's more on the warning: https://teslatap.com/articles/12-volt-battery-compendium/#battery_failur... and the article has more than you'll ever want to know about the 12v battery :)

marcustcohn | November 17, 2019

Slightly off topic but related - I believe the rated miles are a function of kwh times an EPA factor and performance (speed and temperature) have no affect. On a trip the projected line is likely based on the same math but actual performance is a function of whrs/mile. Thus as a cold car warms up there should be some recovery from an the initial projection which in the cold would be on the low side. Please correct of comment on this.

Bighorn | November 17, 2019

Projected is based on the recent past 5/15/30 miles, either averaged efficiency or you can choose the instantaneous option. They will definitely start out high if the battery is warming, but revert to the mean when the resistive element is no longer drawing power. If you have a destination plotted, you can look at future predicted arrival SOC based on all the aspects that went into the initial calculations (Trip option) like average speed on that route and topography. Other inefficiencies get baked in as they are realized such as going faster than anticipated, using climate at 78 degrees or facing a 15 mph headwind. By 30 miles, the predicted arrival SOC should be pretty locked in.

Many things are under the driver’s control. Heat can be turned down or off and seat heaters can be used, battery heating can be turned off or speed can be adjusted up or down depending on the forecasted arrival buffer. Seat heaters draw about 1% of the power of max heating.

marcustcohn | November 18, 2019

So the message 'You are charged enough to go to your destination' (or something similar) does NOT take into account the range lost to battery heating - and of course there is no way for it to calculate Kwh lost to cabin heating. But if I follow then asap in the morning hook up to a SC and super heat the cabin - the battery may or may not get much charge depending on the outside temp but at least you will have avoided draining all those watt hours to overcome a cold night. That sound right ?

Anthony J. Parisio | November 18, 2019

Has anyone here switched to Ohmmu 12 V lithium battery for their car?

Bighorn | November 18, 2019

"You are charged enough" can be a miscalculation for any number of reasons and is why most people have a buffer goal in mind before they are comfortable leaving. Sometimes it needs to be 30% even if the car says ready at 12%. The ready number the car comes up with can be all over the map. Plugging in in the morning to warm the battery will increase the efficiency of the drive and help preserve charge. I wouldn't strategize to this degree if the next charger is within easy reach.
It's the outliers that require a little extra thought. Say the first supercharger requires 92% of the battery to reach it, making a range charge only provide an 8% buffer. You'll want to optimize efficiency by warming the battery and cabin with charge cord electrons. I'd probably also start out going 5 under the speed limit to see if I could raise the arrival buffer to a more comfortable number. Seat heat takes about 50W while the cabin heat is closer to 6000W, which is why you'll hear about bundling up and choosing seat heat over the heater. As the SCs have been built out, these scenarios are becoming much less common.

murphyS90D | November 18, 2019

My first destination is a supercharger 75 miles away. I don't enter the next destination until after I charge the battery so the car has nothing to base an estimate on. Having made the trip to my next destination at least 25 times in the winter I don't even want to know what the car "thinks".

marcustcohn | November 18, 2019

BH and Murphy - great advice -
Murphy - what do you use as a basis for how much to charge in cold weather ? If the actual miles are 100 how many rated miles (kwh) do you want in the battery.
BH - I am hoping that by heating the cabin from an external source I can then switch seat heaters but the WAF will probably require a switch back at some point. So for a 2 hour section I should allow an extra 12 kwh or about 45 miles of range ?

Bighorn | November 18, 2019

6 kW is drawn on max heat. If the cabin is warm and the outside temperature isn’t too frigid, you’ll probably see around 2 kW for maintenance. Depends if you’re negotiating or capitulating. If I’m concerned about running low and my wife is cold, I try to titrate the use of heat to achieve both ends.

marcustcohn | November 18, 2019

BH - well played.

murphyS90D | November 18, 2019

@marcustcohn
I charge to 90% at home before I leave. I use full heat on route to the supercharger to get / keep the car warm. When I first started doing this trip there were no superchargers on my route from the supercharger to the destination which is 200 miles away.. I charge to 90% and monitor the real time trip graph. If my actual is not above the estimate I just use the seat heater until it gets above the estimate. Then I use heat sporadically always keeping the real time graph above the original estimate. If it gets significantly above the estimate I start using heat again. There are now intervening superchargers but they all require significant deviation from my route. Using the "If it ain't broke, don't fix it" policy I continue to use what I know works.
There is a new SC under construction directly on the route and a new one that would require about a 15 mile deviation if I needed to use it. If necessary, slow down until the graph improves.

I keep reading that if you drive the speed limit someone will run into you. I've been driving the speed limit for over 60 years and no one has ever run into me. Granted that for most of that time cell phones didn't exist.

marcustcohn | November 19, 2019

@murphys90D
Sounds like a plan - the initial departure is not an issue - charge to 90+ percent and heat the cabin really well. Then switch to seat heaters until the pilot hears from the passenger. If necessary slow down. At the next SC stop again heat the cabin really well and repeat. I also approve of driving at or very near the speed limit - on some previous group trips I took some flak from other drivers about driving 'at Marc 1' ha ha. From BH is got some great info as to the draw for cabin heating and I can turn that into rated miles so I have an educated guess as to when I heave enough battery to push on.

marcustcohn | November 20, 2019

This is from an email I got from Tesla in response to a cold weather question ----
"Below 0°C (internal battery temperature) the car will not begin to charge until the Battery warms up. Between 0°C and 20°C the car will still charge, but charging rates will be reduced"
They went on to say that warming the car was the best way to warm the battery. Hmm - is that better than driving ?
Zero C is 32 F so if the car sits out overnight it cannot charge until the battery warms ?

Bighorn | November 20, 2019

My understanding is that -4C is the threshold for charging for the Model 3. Not sure if it also applies to the S.
Warming the car will turn on the 6 kW battery heater at a certain threshold, 40F is my best recollection. That heater remains on while driving, so I think it’s accurate to say driving would be as or more effective than heating alone.
Whether the battery cold soaks to 0C overnight in that ambient temperature would depend on when the car was last driven and how warm the battery was when parked.

Tdreamer | November 20, 2019

My use case on this topic is towards the end of the day while my Model X has been parked outside in cold weather I wan't to ensure I have regen for my short 6 mile commute home (Sept '17 pre-raven). If charging is available at work, I'll do so in the afternoon to have that warm the battery. But a recent rapid influx of EVs/PHEVS means there is frequent contention for that charging, and I find it hard to justify plugging in just to have regen. So....

Today about thirty minutes before planned departure I remotely turned on the cabin heat @ 75F (outside temp was about 39F). Wanting to ensure the battery was warm, I then turned on the max defrost option for good measure. One hour later I headed to the car and checked the app: inside temp 106F and max defrost still cranking! Over the course of the day I used 21.24 kWh and lost 65 rated miles in range (almost entirely during this warm-up process).

The regen was great on the way home though.

Greengen | December 3, 2019

When I updated to v 10 the batt temp Guage on the dash has disappeared when in ludicrous mode.
As the auto batt heater never works until really cold so I have virtually no regeneration for many of my winter drives. I used the ludicrous mode to preheat battery while plugged in, I would wait tI'll it got to at least 20 deg , now I have no idea what temp it is and don't want to heat it to 40c .
We should to be able to turn it on from the phone app.
Pre heating batt before I unplug when I am taking long drives in the winter is very useful and should be a simple update to activate and set a temp from the app.
Why did they remove the temp indicator??

Greengen | December 3, 2019

When I updated to v 10 the batt temp Guage on the dash has disappeared when in ludicrous mode.
As the auto batt heater never works until really cold so I have virtually no regeneration for many of my winter drives. I used the ludicrous mode to preheat battery while plugged in, I would wait tI'll it got to at least 20 deg , now I have no idea what temp it is and don't want to heat it to 40c .
We should to be able to turn it on from the phone app.
Pre heating batt before I unplug when I am taking long drives in the winter is very useful and should be a simple update to activate and set a temp from the app.
Why did they remove the temp indicator??