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Cold Weather Charging Until the Timer/App Arrives

Looking for advice here. My car is parked outside in the Midwest & it’s been cold (for me, anyway, ~7F-20F). To charge comfortably, the battery needs to heat itself, if only to 45F(?) or so. If the battery completes charging, it allows itself to get quite cold, my guess is to 20F or so (all guesses, maybe it’s allowed to go all the way to ambient – I need to get a replacement battery for my temperature data logger – Ha!, an excuse to go for a ride!). Therefore, I made a little spreadsheet to help me target my desired charging rate (XX Amps @ 240V) based on (a) remaining “Rated Miles” and (b) how many hours until I intend to drive again, so the battery will /just/ be done charging before I depart in the morning, therefore keeping a bit of heat (45F?) in the car and a having nearly full (standard 80%) charge. E.g., I’m charging at 240V/12A right now because I had 125mi rated remaining & 12hrs before I drive again.

This isn’t a *bad* idea, is it? I’m trying to avoid the big “heating the battery via the battery” penalty and have the car a little closer to my a$$’s preferred temp when I climb in. Any thoughts about if it’s a bad idea to use this approach for a Range charge (more slowly charging toward 100%)? Based on what I’ve read here & on TMC, it should be fine for standard charge, but /maybe/ not so good for a Range charge, which is fine, I wake up & can bump up to 40A 1-1/2 hrs before Range launch.

400mi (newbie) & totally loving it!

Good question for the Tesla " scientists"! I wouldn't rely on the forum format. You paid $100000 for this car and its a brilliant question!

Since you aren't getting far into Range, it's fine. It's the absolute total that counts, not what it's called.

Suggest a minor change to your arithmetic: target having the car "Full" a little AFTER to plan to pick it up. That way it's got no chance to cool off.

typo: a little AFTER you plan ...

While I applaud your creativity I think pressuring Tesla to fix their charging software would be more fruitful. Perhaps an email campaign.

I'm trying same approach tonight, went to 15amps. it may not be slow enough, will see in the am.

murray;
Given. This is pure stopgap till the promised timing control is in place.

The new app includes a battery pre-heat function in addition to cabin pre-conditioning. You will target having the car "full" a little BEFORE you plan to pick it up. It will already be warm.

@Robert22 - are you a beta tester of the mobile app?

No, not a beta tester, but had a brief conversation with headquarters tonight. Some non-revelatory info I've yet to come across (Disclaimer: not enough time to read every post so apologies if I'm repeating):

1. The rollout of 4.2 is indeed batched but not random. Location and climate are factors as are other parameters which makes a lot of sense (VIN # is not one of them). Rollout starts small and gets larger over time if the update is found to be stable. Server capacity is not expected to be an issue going forward. The goal is to eventually distribute just like an iPhone update.

2. Fix for those with a condensation issue will not be time-limited. Plenty of time to assess whether this constitutes a problem or not for each individual owner.

3. Only the senior level people really know when the app is coming. I've seen a post suggesting March which is probably later than currently expected but no way to confirm, think Apple. The battery pre-heat function will be great in northern climates. Today I got my first regen disabled alert and my dashed restriction line jumped from green to orange side i.e. until the battery pack warmed up, it capped the amount of energy available to me.

I'm finding that with this car I don't drive it, I vote. The car then decides what it will allow me to do ;)

It's better to target the charge ending a little AFTER you plan to pick it up. Using the screen to End Charging ensures the battery is power-heated right up to the end.

Just a reminder that Tesla has indicated that you're not actually losing charge in the cold climate (aside from the standard vampire load issue). They've said that their range calculation algotithm currently assumes the battery will stay cold and bases the project range on that, but that within 10-20 min of starting to drive your projected range should actually INCREASE as the battery warms and the algorithm begins to reflect reality.

...also that there will be update to that calculation in some upcoming version update.

As riceudude notes, with a cold battery, some of your miles are temporarily put on ice.

Sorry!

Or not ... :p

I had pretty good results from the slow charging last night. Guessing it finished within an hour of when I checked it this morning (about 15F) and it was at 238 or pretty much at full range of the 90% charge. So to be sure I set the charge to max to allow to to continue while I ate breakfast and it added 2 more miles to 240. I had regen from the start today which was nice. so I think it proves the that that approach does work and can be a stopgap until the scheduling software is available.

Here is the reply to my inquiry to Ted M., who is a Product Planner at TM:

Regen is limited or disabled when the battery is cold because charging a cold battery places increased wear on the battery cells. Similarly, if you were to connect the car to a power source when the battery is cold, the battery will begin a preheat cycle before charging is initiated. When regen is limited, drivers see a dashed yellow line on in the regen portion of the power meter to the left of the speedometer. It's likely that you'll also see a dashed yellow line on the power portion of the scale, as power is also limited when the battery is cold. As battery temp incases, the dashed line will move toward the maximum values of each scale then eventually disappear. That said, it's not explicitly stated anywhere on the vehicle or in the owners documents, what these dashed lines imply. I will suggest that we implement a "regen temporarily disabled" telltale light for the instrument cluster as we had for Roadster.

A future software release will introduce a full schedule for your Model S including timed charging, ready times and perhaps even vehicle behavior settings based on ambient temperature, calendar dates or other factors. Since the mobile app is not yet available, reducing charge current to finish charging just before planned use is the easiest way to ensure the battery is at operating temperature when you want to use it. As you mention, it is slightly less efficient, since chargers are most efficient at their max capacity, but less active cooling is needed at lower current charging so there's a tradeoff.

So I thanked him and politely asked if there was an ETA for the software update and mobile app. I'll post his reply.

noel;
Excellent! You can avoid the last fiddle by timing to finish AFTER you need it so it's still in progress at that time.

Actually, that's not recommended for reasons that should become clear shortly.

Cutting off charging from the screen is not a problem, AFAIK. What reasons could there be? If you charge 250 out of (say) 270 maximum normal full charge, the only issue is how much you need. For daily commutes, few come even close to that distance.

@Robert22 - what do you mean?

The slow charging sounds like a great idea until the mobile app comes out. My car's energy spikes for about 10 minutes in the morning trying to warm up. I'd love to eliminate that.

@Robert22, why do you feel slow charging would not be recommended?

@noel.smyth, You are somewhere from the Philly area? I am in Malvern.

Yes, this is a stopgap technique. Though there might be times you want the car to be drawing steady shore power rather than leaving it up to the car's algorithms to decide when to start bingeing!

@Tony - I am in Havertown, good to see another one in PA!

Here's the good news from Ted M., a Product Planner at TM:

1) The mobile app will be available within two weeks
2) It will allow you to precondition the battery and cabin whether the car is plugged-in or not.
3) That's going to allow you to get into a warm car, get realistic range calcs, and regen immediately.
4) The energy use for #2 is the same whether you precondition or get into a cold car with a cold battery, unless you precondition for too long or your next drive is too short for those events to complete. Hopefully the Ready Time feature is smart enough to figure out how to minimize the energy used so things are good-to-go just before you get in.

Woo Hoo! Thanks to the forum posters for getting this on TM's radar!

Super B! Next, an AI app that uses GPS and temperature to learn/figure/remember whether you will want preconditioning tonight, and when it should complete, and ...

@Getting Amped

Did you get a sense of whether these features will be available only through use of the app, or whether they will be added to the car's software? It would be odd if something like this could not be done from the car itself.

@DouglasR

I get the sense that they will be added to the car software also:

A future software release will introduce a full schedule for your Model S including timed charging, ready times and perhaps even vehicle behavior settings based on ambient temperature, calendar dates or other factors. Since the mobile app is not yet available, reducing charge current to finish charging just before planned use is the easiest way to ensure the battery is at operating temperature when you want to use it.

And when I asked when these things will be available:

The mobile apps will be released in the next 2 weeks. They can be downloaded from their respective app stores (Apple App store and Android store). Timed charging will come in the next software release but I'm afraid I can't be more specific.

I believe he's using the term "software release" to refer to the car OTA updates.

I agree, not everyone has a phone that runs apps. Maybe there should be a Windows program for PC's and a MAC version too? It might be nice to set all this up without sitting in the car while in the garage.

Now that the phone app has been out for a while, does turning on the environmental controls also pre-condition the battery? I still see little or no regen when I first start off on a cold morning. (but I haven't tried pre-heating the car more than 10mins ahead of time). What are others experiences? Or has this been confirmed to not be part of the app yet?


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