DMC-Orangeville
Audi eTron & John Deere 5100E
Me too. This AM = unheated unattached garage, -22C, put on the App heating 20 minutes prior to leaving and had about 50% regen. It took 45 minutes of driving to reach full regen......
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Battery preheat released
- Thread starter Vawlkus
- Start date
Me too. This AM = unheated unattached garage, -22C, put on the App heating 20 minutes prior to leaving and had about 50% regen. It took 45 minutes of driving to reach full regen......
I think there is another reason - the car drives differently when you have zero regen - it doesn't decelerate when you take your foot of the break. That has got me a couple of times in the past couple of weeks since our weather has been so cold to cause zero regen - I have to quickly apply the breaks when I wasn't expecting to need to break.
Yes zero regen is pretty surprising the first time. I remember the very first time I hit that in the Roadster... I slammed the brakes so hard LOL. The thing would just roll and roll and roll...
You’re right about that, but if you preheat on shore power, unlocking that little bit of extra range might be worth it. I don’t have any experience with that specifically. If it rarely happens and the trapped portion isn’t that much, then it’s a non issue and the only reasons to preheat the battery are for charging and a bit of regeneration.
mknox
Well-Known Member
That's exactly what it does now.
I like it when it's on shore power, but wish it would stick to the 30 minute limit when unplugged (or at least be configurable). Sometimes at the office I'll turn it on expecting to leave within the half hour, then get held up and forget about the car. The way it was, I wouldn't waste too much energy, but now it will just keep on using power (until it gets down to 20% SOC).
Yeah totally agreed. There needs to be finer grade control.
One other thing I've long wished for - since the beginning - a pack temperature reading. That would be SO useful for planning winter driving.
I agree, though there is a way with TM SPY if interested.
Using TM-Spy to see Model S data.
Our trip up North last week it was interesting to see the data. I also noted how hot the battery pack would get when supercharging in those cold days. At times, the battery was cooling its self. Quick screen shot of a warm battery. Approx 62 to 65deg is when you have full regen
mknox
Well-Known Member
Knowing how cold it was, I turned mine on by remote about an hour before I left. Looking at my sub-meter logs, it looks like the high spike for battery heating didn't last very long... about 7-10 minutes. Then my power draw tapered down to about 3 kW until I departed. My re-gen was limited to 30 kW (about 1/2) which seems to be typical with the new battery warm-up algorithm.
Unrelated, but I just noticed something odd on my overnight charge profile when I checked on the above. For the last hour and a half of the charge cycle, my power draw dropped from about 9 kW to about 7 kW quite suddenly (i.e. it didn't taper down). Never seen that before
Car is the light green line.
mknox
Well-Known Member
When I got home, I noticed my car's setting had dropped from 40 amps to 30 amps when I went to set my timer. Not sure why it would have done that on it's own during a charge cycle. There was no sudden voltage sag (red line in my graph above).
Looking again at my charging data for the last week, and assuming that my battery temp is the same as the "outdoor" temperature reported by my car, it appears that the battery warm up time can be approximated by this formula:
So at -5 it will take about 20 minutes to warm up the battery before you can start charging.
Code:
Warmup time (in minutes) = 15 - temp , where temp is in Celsius.So at -5 it will take about 20 minutes to warm up the battery before you can start charging.
Thing has a hair trigger. All it takes is a momentary drop and it will pull back.
Time depends both on outdoor temperature and windspeed, given that the pack is completely un-insulated. People have observed negative charge rates in the past on cold windy days outdoors.
I am assuming that most Tesla owners park in a garage overnight where they have their charger - just like I do. The purpose of this analysis is to help refine the algorithm for determining the time to start a charge when you want the charge to end at a specified time. I want my charging to end every day at 7am - that is 10 minutes before I leave for work and that is also the time that my electricity rate goes up.
If you know your desired end time, charge rate, temperature, current SoC and final SoC then you can calculate a time to charge and start charging at that time.
If you know your desired end time, charge rate, temperature, current SoC and final SoC then you can calculate a time to charge and start charging at that time.
mknox
Well-Known Member
FWIW, at 40 amps, I "ballpark" 1 hour for each 10% SOC and that has served me well for approximating my start/stop times. It usually stops around an hour or more before I depart, but I just hit the remote HVAC before I jump in the shower.
If you are charging the primary method of heating the pack should be charge waste heat which you can approximate as 10% of total charge energy. This will also help you avoid the pack heater entirely, as it's quite a lot of energy. If you charge 50kW, you get roughly the equivalent of running the pack heater for an hour.
If I remember correctly at 80A I was using an SOC rate of 0.3%/minute - so one hour would give 18% - similar to what you have assuming that it scales with current.
I have since dialed down my HPWC to 70A as the cable/connector were getting seriously hot. But this is less of an issue when the ambient temp is -10C.
I wrote some code that had two modules. Module1 would run at 1:00 to check the SoC. It would then determine what time that charging would start and set a Cron job on the computer for Module2 to run at that time. The Cron job would run and start charging manually at that time - I didn't use the Tesla scheduled charge time feature as you cannot set that via the API. I am now adapting that code to add in the temperature adjustment.
I have since dialed down my HPWC to 70A as the cable/connector were getting seriously hot. But this is less of an issue when the ambient temp is -10C.
I wrote some code that had two modules. Module1 would run at 1:00 to check the SoC. It would then determine what time that charging would start and set a Cron job on the computer for Module2 to run at that time. The Cron job would run and start charging manually at that time - I didn't use the Tesla scheduled charge time feature as you cannot set that via the API. I am now adapting that code to add in the temperature adjustment.
Variables are pack revision, degradation, car and drive model, and utility voltage after sag. I'm getting a smidge over 20% per hour.
Just wasting energy this way, as the efficiency drops off as you reduce current for a few reasons. I^2R losses are minimal. Try cleaning out the connectors.
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