Happy New Year fellow Tesla forum members. I recently picked up a Model X 75D and have a question on the battery capacity and consumption. Based on the trip information and kwh used since last charge, I feel that the capacity on my battery isn't anywhere near 75kwh. For instance, I charged my vehicle to 80% last night and drove about 18 miles on a trip using 6.6kwh, which equates to approximately 360Wh/mi and that seems pretty normal given Southern California weather conditions. However, my battery went from 79% charged to 69% charged, which is 10% of the battery life. If 6.6kwh is equal to 10% of my battery life, that would imply my battery capacity is only 66kwh. I’ve noticed a very similar battery usage numbers since I picked up the car 3 weeks ago. Is anyone having the same experience or is there a potential issue with my battery? If the consumption meter and battery life % figures are accurate, Im only getting 66kwh battery capacity.
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Battery Capacity / Consumption Question
- Thread starter SC626
- Start date
Track your driving and consumption for a month or so, and use the aggregate numbers for your calculations. Using one short drive will give you wildly variable numbers. For what it may be worth, my X and previously S both deliver the range and capacity promised.
If you're convinced that yours is not doing so, bring your data to your Tesla Service and they'll happily help you figure out whether something is wrong with your data, or with your car.
If you're convinced that yours is not doing so, bring your data to your Tesla Service and they'll happily help you figure out whether something is wrong with your data, or with your car.
Thanks Rodolfo. I have an appointment later this month with the service center. While a short drive isn’t necessarily a good example, I’ve tracked this over the past couple weeks and have imputed an average capacity between 66-67kwh based on the data. I just used today as an example because it was an easy 10% battery loss after using 6.6kwh. I love the car so far, but between the battery capacity, steering wheel shaking when hitting bumps at over 40mph and a rubber door seal falling off, I’m a little disappointed.
I've had Teslas (R, S, X) since August 2011. They're a young company and they make mistakes. But overall, they tend to be extremely interested in making things right, fixing their mistakes and failures, and keeping you happy. My experience would indicate they'll take good care of you. Hold them to a high standard and don't settle for crappy quality issues; they'll make things right, I believe.
Whisky
Member
The trip computer doesn't include other consumption beyond the energy used to drive the car. If you're taking a cold battery out, for example, energy is used to heat the battery up to optimum level. If you're using a lot of heating, the same is true. Kind of like if you drive a gas car, your car will estimate your miles/gallon but if you ever did the math, it would never work out. EVs do have closer to rated (but still not close to rated) range on long distance driving, but for short trips, the consumption is always somewhat ridiculous. That's especially true with the MX (I have the same car).
You can, and should, check with Tesla is you suspect an issue but 10% used for 18 miles seems about right especially when you consider there's some rounding in there that makes this math entirely inaccurate. Its' also true that the car spares away some battery the closer you get to 0 so you never quite get to 0, and that rated range at 100% goes down at a faster rate than rated the closer you get to 0% but in your example that's probably not yet taken affect (ie, 100% assumes the full battery size, but when you get to 0% there's still a percentage left of the battery that the car won't let you access for driving).
Anyway, it really is best to just enjoy the car and not stress too much over battery consumption.
You can, and should, check with Tesla is you suspect an issue but 10% used for 18 miles seems about right especially when you consider there's some rounding in there that makes this math entirely inaccurate. Its' also true that the car spares away some battery the closer you get to 0 so you never quite get to 0, and that rated range at 100% goes down at a faster rate than rated the closer you get to 0% but in your example that's probably not yet taken affect (ie, 100% assumes the full battery size, but when you get to 0% there's still a percentage left of the battery that the car won't let you access for driving).
Anyway, it really is best to just enjoy the car and not stress too much over battery consumption.
Actually, I think it does. I have noticed that my Whr/mi numbers are in the 400's for the first few miles of every trip even though the power meter is showing low or negative draw. This coincides with the time it takes the cabin to warm up. The heater draws as much as 5.5 kW for the fist 3 - 5 min, and gradually tapers down to about 1.5 kW after the cabin is close enough to the setpoint that the thermostat is regulating. This takes 15 - 20 min.
Uncle Paul
Well-Known Member
Orange County has been relatively cold the last weeks. Down into the high 20's.
If your garage is unheated, the car will use the battery power to warm up the batteries and interior for the first several miles. This will dramatically reduce your mileage. Kind of like how a cold ICE engine runs the choke for a richer mixture until everything warms up.
A little tip is to charge up your battery a bit before heading out on a cold morning. This way you can have your house current used to warm everything up and start our with everything nice and toasty. Will really show up by extending your mileage.
If your garage is unheated, the car will use the battery power to warm up the batteries and interior for the first several miles. This will dramatically reduce your mileage. Kind of like how a cold ICE engine runs the choke for a richer mixture until everything warms up.
A little tip is to charge up your battery a bit before heading out on a cold morning. This way you can have your house current used to warm everything up and start our with everything nice and toasty. Will really show up by extending your mileage.
Whisky
Member
Well look, either you have it all figured out and Tesla sold you a 66kWh battery or there’s an energy consumption not being taken into account by the metering you’re basing this assumption on. Pretty much every long time Tesla driver here has told you short trips aren’t indicative, and one of the reasons is the energy required for battery conditioning with a cold or hot battery.
At this point your only choice is to go back to Tesla and share with them your math, and they’ll tell you the 6.6 number doesn’t include all the energy the car has used during the trip and you’re back to where you started.
To look at it differently, switch to rated range and charge to 90%. If it’s 90% of rated range (within 5 or 10 miles) you’re doing terrific. If it’s significantly less, you’ve got something to go to Tesla with.
You have quoted No. 8 but seem to be responding to No. 1 (where the 6.6 number appears) so a little confused here.
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[QUOTE="Uncle Paul, post: 3318742, member: 18019"
If your garage is unheated, the car will use the battery power to warm up the batteries and interior for the first several miles. This will dramatically reduce your mileage. [/QUOTE]The numbers and times in No.8 were with the car's cabin temperature initially 10 ° F below desired and desired representing a 20° rise re ambient. Integrating under the power consumption curve to equilibrium and using 1.7 kW for heater load thereafter I calculate that the heater would use about 2% of the 100 kWhr battery pack in a 3 hour trip. Now that's stationary with a 20 ° rise. With a 50 ° rise required we'd estimate the steady state demand at 2.5 times what it is for 20 ° and get a rough figure of 5% of the battery for a 3 hour trip. That doesn't seem too dramatic.
If your garage is unheated, the car will use the battery power to warm up the batteries and interior for the first several miles. This will dramatically reduce your mileage. [/QUOTE]The numbers and times in No.8 were with the car's cabin temperature initially 10 ° F below desired and desired representing a 20° rise re ambient. Integrating under the power consumption curve to equilibrium and using 1.7 kW for heater load thereafter I calculate that the heater would use about 2% of the 100 kWhr battery pack in a 3 hour trip. Now that's stationary with a 20 ° rise. With a 50 ° rise required we'd estimate the steady state demand at 2.5 times what it is for 20 ° and get a rough figure of 5% of the battery for a 3 hour trip. That doesn't seem too dramatic.
Whisky
Member
I think you’re still missing the point we’re trying to make: The Tesla Model X and S (not the 3) have a heater under the car specifically for the battery. When you start the battery cold, energy is to heat the battery, in addition to the interior. This is why it was suggested you charge the car before you drive if you’re really concerned about efficiency on short-trips, because charging the car before departure will warm the battery (turning on climate also does this, but only at temperatures closer to freezing). As an example, on particularly cold days in Canada when I’m running lots of errands, I’ll charge my car to 80% overnight and then add that extra 10% before driving out so I still have regenerative breaking and so my energy consumption isn’t as dramatic for the first 30 minutes of the trip.
Is this heating is only active when you charge in cold conditions?
I typically start charging at 1 AM, and it completes in an 1 hour or so. And now that morning are below 50F, every morning I have the warning dashes on the regen side of the meter. They don't go away until I have driven some 15 miles.
And is there a way to set the car to do this 2 step charging. Or are you doing it manually with the app?
Whisky
Member
Heating runs as-needed during charging and driving. If you have limited regenerative braking, your battery heater is almost certainly running.
I do it manually, but I don't drive on a regular schedule. If your charging is predictable, you can set it up to run at 6am and charge through until you leave at 7pm (or whatever the time shift is). When it gets extremely cold up here in Canada, that hour is crucial, because sometimes with even an hour of charging the battery won't be warm enough and regenerative braking will take a while to return, plus the added inefficiencies of driving without regenerative breaking etc..
Yes it would but your battery didn't go down by 10%. It went down by something between 9 and 11% and there is no way to tell where in that range. Pessimistically, 6.6 kWh is 11% of 60 kWh. Optimistically, 6.6 kWh is 9% of 73.3 kWh. This uncertainty arises from the quantization (rounding) of the numbers presented to you. The kWhr number is rounded too. Thus the actual kWhr could have been as high as 6.65 and the display would still read 6.6. The absolute best case, based on the data displayed to you, would be that the battery capacity is 6.65/.09 = 73.9 kWhr.
Now we do have to recogngize that the probability of the most optimistic rounding error is unlikely as is the probability of the most pessimistic. If you consistently get low numbers then there must be a problem but not necessarily with the battery but rather with the firmware that computes the percentage numbers or the sensors that measure voltage and current in order to compute the numbers. I'd keep an eye on it and if the perceived situation continues, talk to Tesla about it. Keep a notebook in the car.
Another thing to keep in mind here is that Li battery voltage does not decrease much until the cells are nearly fully discharged. This makes measuring the SoC of a lithium battery pack difficult. In addition to the rounding errors inherent in the integer percentage display there may be errors in the numbers before they are rounded.
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A wise man posted here several years back "Believe it if you got it from Tesla - in writing". Based on that I firmly believe the battery heater is active when you are in Maximum Battery Power mode. Other than that I can only speculate.
Lithium ion batteries have fantastic Coulombic efficiency (over 99%) but their energy efficiencies are lower than that. They do warm up when being charged or discharged from Ohmic losses. Besides that the things that are supplying (OBC) current to them or discharging (inverters) them are less that 100% efficient and so also produce waste heat which is removed by a glycol loop which also passed through the battery pack. If the glycol gets too hot a radiator is switched into the circuit and if that's not enough an evaporator. If the battery is too cold it makes sense to bypass the radiator and retain the heat in the loop. If it's way too cold it makes sense to kick in the battery heater which is also in that same glycol loop.
I'd say the strategy would be to leave your car plugged in at night and set for charging to start about an hour before you leave as you have determined it takes about an hour to complete. If you have a 48 A charger the car will draw 11.5 kW and, assuming overall energy conversion and charging efficiency of 90% that will amount to 1.1 kW waste heat.
If you leave the house and the dashed lines show in the regen area of the power meter the battery is not warm enough. It will warm pretty quickly though as the car may be drawing say 50 kW and 10% of that is 5 kW waste heat which will presumably warm the battery. Will the battery heater come on under these circumstances? There is an easy way to find out. Monitor the energy being used. Turn off cabin heat for this check and monitor Whr/mi. You should have a pretty good idea what you consumption is where especially on your normal drive to work. If consumption is 100 - 200 Whr/mi higher than normal early in the trip and then drops to normal after 15 minutes or so then the battery heater ran. Another quick check is to back way off on the accelerator when going down a hill. You need to sustain this for long enough for the consumption app to get a couple of data points. Positive power consumption when going down hill is a definite indication that power is being consumed by something other than the motors. If cabin heat is off then it's not cabin heat and must be the battery heater.
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