It was in the 50s, raining, windy, and I was about 30+ miles into my trip when I got the Pre-conditioning notification and saw my bat % dropping quicker than expected. I knew on a normal day I would be at less than 10-15% charge when I arrived at the supercharger but with the conditions, I knew it was going to be tight. Turned off navigation so it would stop preconditioning and arrived at 6%. I'm not sure if I would have made it if it had continued with pre-conditioning that many miles from my destination. Usually, I see the preconditioning notification somewhere at 20 miles or less, but now I'm seeing the notification much further away from the destination. Has anyone else experienced this?
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Why is my battery pre-conditioning for Supercharging 90 miles from the charger?
- Thread starter GLM3
- Start date
I have had the same experience with the seemingly extremely early onset of preconditioning. I cancelled navigation to the supercharger and then retried navigating to the same supercharger, with the preconditioning starting instantly, and 38 miles from the supercharger. I wish I could pinpoint when this began, and if it started as a result of an update.
bsf29
Member
I had a similar experience on my last trip. I wanted to skip the 1st charger and get to the next one so I also turned off navigation. Precondition will turn on based on how long it will take to warm the battery to optimal charging temp. I don’t know if it will turn off if the SoC is too low to make it to the charger.
Jeremy3292
Active Member
vogz
Member
I had this happen over an hour from the next supercharger on our route on a 38F day last month. I cancelled nav to the supercharger and waited until we were about 25 minutes away and let it precondition from there. I've found that 25-30 minutes of pre-conditioning is plenty in almost all weather conditions. When we arrived at the 150kW supercharger my car started charging at 142kW @ 18% SOC and I probably saved 10% of my battery by not letting it precondition over an hour from the supercharger.
Jeremy3292
Active Member
Preconditioning doesn't even remotely use anywhere near that much battery.
vogz
Member
It said I would arrive at the supercharger with 8% when it starting preconditioning and upped my watt hour per mile from just over 300 to 430. I actually arrived with 18%. I'm not super great with math, so tell me, what is the difference between 8 and 18%?
But HVAC takes the most energy right after you get in the car, and the cabin temperature is the farthest from the set point. Energy usage then dramatically drops off as it takes far less energy to maintain a temperature than to change the temperature. Isn't it logical that preconditioning could operate the same way? If it's initially pumping 7kW into the batteries through the heat pump, do you think it's going to do that for the entire 200 miles? I doubt it.
vogz
Member
Once I let it start preconditioning about 25 mins out from the supercharger, my energy usage again shot up over 400 wh/mi and never dropped until I exited the highway, so no, it clearly doesn't work in the same manner as HVAC warming up the car initially and then not working as hard.
That doesn't tell me anything, except that preconditioning the battery takes >= 25 minutes. What if you preconditioned it for 60 minutes? 90? 120? The HVAC system is designed to quickly (within 3 to 5 minutes) raise or lower the cabin temperature. However, it was not designed to quickly raise or lower the temperature of the battery, and the battery has a much higher heat capacity than the cabin.
I sincerely doubt 7kw is put to a heat pump. That statement alone might disqualify you on making energy use statements. Arguably, living in "SF bay area" wouldn't make you super experienced either.
Also, the majority of model S's do not have heat pumps so that is another issue.
Tesla does some really strange things sometimes with energy use and it tends to be battery protective - or at least we assume that. Tesla has been chopping our cold battery regen for years. Now that doesn't mean it won't allow full speed supercharging on a 60 degree battery but it might not be the absolute best thing for a battery. So having full speed at a certain temp doesn't mean it is actually best either.
Arriving at a supercharger with 6% sounds perfectly fine to me.
But overall, I would probably nav to supercharger for about 30 minutes. I get the impression that Tesla is overdoing the battery heating like it overdoes many other things.
Also, the majority of model S's do not have heat pumps so that is another issue.
Tesla does some really strange things sometimes with energy use and it tends to be battery protective - or at least we assume that. Tesla has been chopping our cold battery regen for years. Now that doesn't mean it won't allow full speed supercharging on a 60 degree battery but it might not be the absolute best thing for a battery. So having full speed at a certain temp doesn't mean it is actually best either.
Arriving at a supercharger with 6% sounds perfectly fine to me.
But overall, I would probably nav to supercharger for about 30 minutes. I get the impression that Tesla is overdoing the battery heating like it overdoes many other things.
smatthew
Active Member
I'm so glad I have a LR RWD. It starts preconditioning an hour out from the first supercharger - but what that mostly means is that it's stopped using the radiator and is letting the battery pack soak up all the waste heat. While driving it's at most a 1kW load - or about an extra 14 watt-hours/mile at 70mph.
While driving, my battery pack warms by about 1 degree per minute, so if I'm starting with a 50 degree battery I do in fact need a full hour of preconditioning in order to be able to supercharge at full speed.
If I'm navigating from supercharger to supercharger the second supercharger might not get any pre-conditioning message until 5 minutes before I arrive - but the car is still keeping the batteries toasty in preparation for supercharging.
While driving, my battery pack warms by about 1 degree per minute, so if I'm starting with a 50 degree battery I do in fact need a full hour of preconditioning in order to be able to supercharge at full speed.
If I'm navigating from supercharger to supercharger the second supercharger might not get any pre-conditioning message until 5 minutes before I arrive - but the car is still keeping the batteries toasty in preparation for supercharging.
vogz
Member
vogz
Member
Simply driving the car warms up the battery, albeit more slowly than pre-conditioning does, but it still warms it up. I can start a drive in the cold with very little re-gen and within 20-30 minutes I have full re-gen. Your neatly fit narrative would only apply if they battery didn't heat up at all in the time between when the car first attempted to precondition about 65 minutes from my destination and when I let it precondition about 25 minutes from the destination.
Jeremy3292
Active Member
I think the overall point here for me is that if anyone thinks they know more about their Tesla and how it works more than the actual Tesla engineers who decided how and when to precondition the battery for supercharging, than that is fine and carry on as usual.
I'll trust Tesla over people on the internet (no disrespect).
I'll trust Tesla over people on the internet (no disrespect).
It makes no sense to me that the car would be dumping heat ,via the radiator, in any circumstance with cell temps around 50F. Have you verified the radiator valve position via SMT when the battery cells were between 50F and 80F.
Using SMT, I almost never need much, if any, preconditioning. I try to arrive with a mid cell temp of around 85F and a max charge rate of 140+KW. Doing this, the initial charge rate given a low SOC, will be nearly 150KW. I arrived at a V3 Supercharger with a mid cell temp of 90F and max charge rate of 170KW and the initial charge rate was 248KW.
It is possible that doing the above is not ideal but my car still shows 307 miles at full charge at 37K miles.
The rear motor 4KW afterburner normally stops after about 15 minutes at the start of a charging session. Not sure if that helps much because the heat generated from DC fast charging is WAY more that the motor windings could ever generate.
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vogz
Member
You are missing the point. I don't think anyone here is saying they know more about their car than the people who designed it. Simply put, I've found excessive pre-conditioning to be an unnecessary drain on battery charge (for me) which leads to longer charge times (charging from a lower SOC) with no discernible increase in charging speed.
I simply have enough cushion in my supercharging to allow for a 10% ish delta for any number of various reasons preconditioning, rain, headwind, stopped in traffic, etc.... Then let the car do it's thing. If I'm no Electrical Engineer and I'm not going to second guess Tesla Engineering on this particular issue.
Apparently 7kW is what the drive unit can do, if it is "stalled" to produce heat. And this is what would happen if it's < -10°C outside. What I'm saying is, I don't think the drive unit would be stalled to the extent of producing ~7kW of heat, for 200 miles, all the way to the supercharger. Eventually, the battery gets heat saturated (hits the target temp) and the drive units can start producing less heat. If the heat pump is used to heat the batteries, then it would take less than 7kW to get 7kW into the battery obviously. I ran a test during the winter where I deliberately turned on preconditioning but kept the cabin climate controls OFF to see whether the heat pump is capable of extracting energy from the atmosphere and sending it to the batteries (in a previous post, based on the videos on the heat pump, I said it appears to not be capable of such a heat flow). But I felt extremely cold air coming out of the radiator and being exhausted around the area of the front tires, suggesting that it indeed is capable of doing this.
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