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Cold weather trip; Considering avoiding Nav directly to SC to avoid preconditioning
- Thread starter SilverStar
- Start date
It pre conditions still , the even though you are near to SC, I had my preconditioning even I was die to 4% when it it re-routed my another SC during the Christmas holiday 2023.
Interesting observation from a trip yesterday. I started with a cold battery. I had about 50 miles to my first Supercharger stop. I did not precondition. I was surprised because it would always do going on the same trip the previous days. When I arrived I understood why it didn't warm up the battery. It was one of the old urban Superchargers that are limited to 70 kW. The car knew of the limited charge rate and didn't waste energy heating up the battery.
Of course I was not happy with slow station. I looked for the next 250 kW station while I charged for a few min and continued my trip. Now the car started preconditioning right away. That is proof the car is aware of the different charge rates available at the superchargers and will precondition just enough.
I changed the destination to a restaurant next to the supercharger and it stopped preconditioning. It also changed my arrival from 7% to 9% battery left. That's aprox 1.6 kWh of energy saved.
Of course I was not happy with slow station. I looked for the next 250 kW station while I charged for a few min and continued my trip. Now the car started preconditioning right away. That is proof the car is aware of the different charge rates available at the superchargers and will precondition just enough.
I changed the destination to a restaurant next to the supercharger and it stopped preconditioning. It also changed my arrival from 7% to 9% battery left. That's aprox 1.6 kWh of energy saved.
But it will use up the buffer, that I spent extra charging time putting in.
That’s a real cost, apparently unnecessarily using up a stuck-in-the-ditch/traffic jam safety buffer.
Interesting, I just did a 7000km road trip over Christmas holidays and the car never displayed the precondition message below 20%. However it was hot and many many hours at highway speed.
Another observation - the SC were very busy and mostly limited to 64kW - could be the reason why?
On road trips the battery is usually warm enough just from driving. Long driving and charging keep the battery pretty toasty, especially when it's also warm outside. I've done countless road trips while running ScanMyTesla looking at the battery temperature.
Since the charge rate scales down with temperature of the battery it's hard to say. At 0 degree Celsius, the battery doesn't charge at all. At 45 C it charges at max. Of course state of charge also matters. So we have two variables: battery temperature and state of charge. The car doesn't tell you what the battery temperature is unless you go into service mode or use another tool. And then there is the variable of the supercharger station. How busy is it and how much can it supply.
EVer Hopeful
Active Member
It would certainly make sense that whatever the maths said, it would ensure you actually made it to the Supercharger
UncleCreepy
Member
Given that a dual-motor Tesla uses roughly 7 kW for preconditioning, it would take about 3.5 hours to burn 25 kWh. Do you have the numbers for the heat capacity and weight of the battery? I'm not saying you're wrong, but 25 kWh seems so out of range that I would like to run the numbers myself.
Also, one other data point that hasn't been mentioned so far: SC sessions used to be billed by the minute. No preconditioning resulted in longer charging time and therefore higher costs. Now that we're billed by the kWh, the charging time doesn't matter anymore (except that we need to charge longer to make up for the energy used for preheating).
Personally I think that preconditioning still makes sense. It limits the time we're blocking a SC stall, and if it's a factor, it also gets us back on the road sooner. As others have mentioned, driving warms the battery, too. That's the main reason why I don't usually precondition more than 30 minutes. Obviously, that also depends on other factors such as distance driven, outside temperature etc.
SOC is always low when we arrive, 10-20%. Since we regularly do the trip, I should be able to check historical data for outside temp as well. The stations are never in use when we arrive either. Next trip I'll be more thoughtful about what is happening and report back.
The danger with charging a Lithium-chemistry pack in cold weather is Lithium plating. That is probably the worst thing one can do to one’s battery, is largely irreversible, and if the rate of charge – the C-rate – is high enough that phenomenon will begin even at fairly modest temperatures.
DC Fast Charging, by its very nature, produces higher C-rates. Tesla’s BMS will largely – but probably not entirely – prevent C-rates that are detrimental.
Heat is normally a very bad thing for Lithium batteries because it accelerates degradation. The only scenario where one would want to suck it up and endure that heat (and its associated pack degradation) is when DC Fast Charging. Lithium plating is a dire condition and you want to avoid it at all costs.
Ergo preconditioning.
Driving alone will not get pack temps high enough that one does not need to precondition. Even a road trip, where one is driving for hours on end, will not get the pack remotely as hot as a fully-preconditioned-on-the-way-to-a-Supercharger pack.
Thermal management of a large Lithium pack such as Tesla uses is rather inefficient. It uses waste heat from the stators to warm the pack. It neither heats nor cools very rapidly. That’s why preconditioning typically takes a while.
Slower charging (lower C-rates) do reduce the likelihood of Lithium plating. That’s why the BMS reduces the charge rate if the pack is not fully preconditioned. Unfortunately, the science of when Lithium plating begins to occur is not exact. Which is one of the reasons Tesla’s BMS is not totally protective.
Charging a Lithium battery in cold temperatures is inherently risky business. Trying to fool or avoid preconditioning when heading to a Supercharger is certainly a questionable practice.
DC Fast Charging, by its very nature, produces higher C-rates. Tesla’s BMS will largely – but probably not entirely – prevent C-rates that are detrimental.
Heat is normally a very bad thing for Lithium batteries because it accelerates degradation. The only scenario where one would want to suck it up and endure that heat (and its associated pack degradation) is when DC Fast Charging. Lithium plating is a dire condition and you want to avoid it at all costs.
Ergo preconditioning.
Driving alone will not get pack temps high enough that one does not need to precondition. Even a road trip, where one is driving for hours on end, will not get the pack remotely as hot as a fully-preconditioned-on-the-way-to-a-Supercharger pack.
Thermal management of a large Lithium pack such as Tesla uses is rather inefficient. It uses waste heat from the stators to warm the pack. It neither heats nor cools very rapidly. That’s why preconditioning typically takes a while.
Slower charging (lower C-rates) do reduce the likelihood of Lithium plating. That’s why the BMS reduces the charge rate if the pack is not fully preconditioned. Unfortunately, the science of when Lithium plating begins to occur is not exact. Which is one of the reasons Tesla’s BMS is not totally protective.
Charging a Lithium battery in cold temperatures is inherently risky business. Trying to fool or avoid preconditioning when heading to a Supercharger is certainly a questionable practice.
I don't know about situation where you have no choice but to go long stretches to the nearest charger, but if you're skipping chargers and trying to avoid pre-conditioning... maybe reconsider.
teslamotorsclub.com
Chicago area superchargers failing in cold
News story Seems like they can't handle the -15 fahrenheit temperatures. I had no problem the day before across the Wisconsin border when it was -7. Lucky I'm not traveling now. Anyone have details why they are failing?
teslamotorsclub.com
During my road trip last month (temps were a few degrees above freezing), I noticed my 2023 M3 would start preconditioning about an hour and a half before my arrival to the SC. Normally I wouldn't care, but on a few occasions it estimated I would arrive at the SC with a very low SoC (like 6%) so I stopped the navigation then started it again when I was about half an hour away from the SC. Does it really take an hour and a half to precondition? I would have expected the system to be smart enough to not precondition if that results in risking running out of battery, but apparently not. I am disappointed that there is no way to turn off or at least adjust the preconditioning, most times I don't care if it takes me an extra 15 minutes to charge. I wonder if Tesla is intentionally making it use more battery so that they can make more money by having you charge more.
Does anybody know if it preconditions harder when it has less time? I mean if you start navigating to a SC when you're 10 mins away, will it precondition harder than if you start navigating an hour away? I would guess not, there's probably a maximum rate at which it can heat the battery to avoid damage, but who knows.
Does anybody know if it preconditions harder when it has less time? I mean if you start navigating to a SC when you're 10 mins away, will it precondition harder than if you start navigating an hour away? I would guess not, there's probably a maximum rate at which it can heat the battery to avoid damage, but who knows.
Contrary to what is written in a post above, you will not cause any damage by charging without preconditioning. Just a few days ago I stayed at a hotel in sub-freezing weather, when I left the hotel in the morning I navigated to a SC 10 mins away. When I plugged in, it would only charge at 5kw. It stayed at 5 for about 20 or 30 minutes before it climbed up, and it took me well over an hour to get to 80%. So the system is smart enough to limit the charge rate to avoid damage to your battery. That said I would always precondition, the only time I don't is when I am worried I won't have enough to make it to the SC, which has happened a few times on road trips. Also if staying at a hotel in the winter, it's probably smarter to charge before arrival when your battery is still hot, rather than in the morning when it will be very cold. Or better yet find a hotel that provides a charger (why are those so rare?).
I asked ChatGPT how much energy it takes to warm up a 500 kg body (approx weight of a Tesla battery).
One thing to keep in mind when calculating the energy needed for preconditioning is that the car uses the heat pump. Depending on the ambient temperature, it's coefficient is 1:3 or 1:4. So it would need only 1 kWh of electrical energy to 'produce' 3-4 kWh of heat energy going into the battery. Going back to my somewhat extreme example of heating the battery from 0 C to 45 C, it would not need 25 kWh.
Either way, I agree, preconditioning is a good thing and that's why Tesla does it by default. It makes for a better experience as a driver needing to charge. There are not many situations where I want to turn it off.
The proposition isn’t to -avoid- pre-conditioning. It is delaying pre-conditioning.
While 20 min seemed probably enough out ahead, and the BMS wasn’t giving me a nag to make sure to pre-condition ahead, I’ve switch to 40 min out. I don’t have the exact optimum charge rate curve memorized, but when I initiate the SC it is giving a rate that I can’t discern from optimum.
PS FWIW I drove my 3 over 2 years, 80K-90K miles of which probably 35K-40K were SC, without pre-conditioning being a thing.
ZenRockGarden
Active Member
I agree - claiming that charging without preconditioning causes damage is a huge reach.
What IS clear is a trade off in charging time. Basically you're giving up some stored KWh's to be in a condition where filling up will go faster. This means shorter stops - especially charging in the 0-50% range which is typically good on long travel.
I’m not seeing that, when I delay
Edit: For clarity; What I see at -20C in the dark over 82mi highway route is saving 7kWh by delaying preconditioning until 40mi remaining, full speed charging at the end
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