I would never do that. I'm just trying to understand as much as I can. I've seen videos of people running range tests where they go down to zero and continue until the car stops. I'm just wondering if the BMS calibration is off, would the missing percent of charge allow the car to travel further below zero percent than an identical car that is accurately calibrated. Again, I only ask this question for educational purposes only.
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Using Lower Half Of Battery
- Thread starter dusty22
- Start date
I would never do that. I'm just trying to understand as much as I can. I've seen videos of people running range tests where they go down to zero and continue until the car stops. I'm just wondering if the BMS calibration is off, would the missing percent of charge allow the car to travel further below zero percent than an identical car that is accurately calibrated. Again, I only ask this question for educational purposes only.
ElectricIAC
Good-Natured Rascal
AlanSubie4Life
Efficiency Obsessed Member
Probably it would have some impact. To some extent that is the reason for the 4.5% buffer (which is being demonstrated in these videos). Don’t want to run out before hitting 0%, and the buffer enables this to easily be avoided.
But in general the estimate is really remarkably good so it usually would not have any practical effect, and you’d be able to access 4% or so below 0%, if you were very careful, some of the time, and you did not mind being stuck by the side of the road, or in the middle of the road.
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Sure, I won't hesitate to use 100% of my battery, but charging to close to 100% all the time when you don't really need to is a good way to lose that capacity, just like filling a plane's fuel tank to 100% all the time is a good way to waste money (since it takes fuel to carry fuel)...and that's if you aren't over maximum landing weight at your destination, in which case, you will waste even more money (plane must be inspected and parts may need replacement due to landing overweight).
If you can keep it under 50%, then keep it under 50%. But you can't do this exclusively or your BMS will drift and your estimates will be off. I find that charging to 100% once every 3-4 months and then immediately driving it to get the SoC back down is a good practice though.
Does the BMS only calibrate at 100%? If one consistently sets the charge to 50% and a new M3 consistently shows half of its rated range, is the BMS calibrating at 50% ?
The BMS needs to see voltages at both ends, empty and full, while the car is off so it can estimate the capacity properly. Balancing cells however, to resolve inconsistencies, happens at high SOC (90+).
AlanSubie4Life
Efficiency Obsessed Member
Notably this balancing does not change the accuracy of the BMS estimate. It just changes the available energy.
I don't know if this proves anything, but for whatever it's worth,. I charged my battery to 90% and ran it down to 20% over a week or so. Connected it to a 120v outlet, charged it to 50%, and the miles displayed 181. It usually displays 179 mi at 50% charge (car is a 10 month old 22 M3 LR with just over 4k miles.
AlanSubie4Life
Efficiency Obsessed Member
Rounding error. Max it can display is 358 or so (brand new owners can verify if it is 358 or 359). So max at actual 50% that it can display is about 179/180.
You do not need to charge to
90% by a regular basis.
Just continue what you do and if you see a big range drop you might be able to recakibrate the BMS if you feel the need.
The real range is still there even if the BMS is off.
Keeping low like you do is good for the battery longevity.
Update... drove the car about 40 miles then charged it back up to 50% and it displays 178 miles. Would that extrapolate to 356 miles if I charge up to 100% ?
Yes, but what you really care about isn't miles, but usable energy in the battery. Go to the energy app on the main display and select Consumption/Average Range/30 mi. You'll see an average Wh/mi and projected range. Multiply average Wh/mi * projected range and you get the total number of Wh currently in the battery, as estimated by the BMS. Divide it by 1000 and you'll get the total number of kWh currently in the battery. Then divide that by the fraction of energy in the battery (i.e. if the battery is at 35%, then divide by 0.35) and you get the total number of usable kWh in the battery. And remember that these batteries are supposed to have 75 kWh of usable energy when new.
Approximately, +/- a few miles. I charge to 60%, but the extrapolation for estimated range bounces around within about 8 miles, from 306 to 314 miles. The original EPA estimate is for 310, so you can see, it fluctuates around 310, as the best fit line shows.
First of all, miles at the battery symbol is energy. Each mile is a certain numer of Wh, so there is no need to perform a energy app calc.
The miles tells the same. If we know which year the M3 is, we can calculate the energy in kWh from the miles.
If we do the energy app calculation we get the whole battery capacity including the buffer. So we do not get the ”usable energy”.
A US M3 LR (or P) did have 77.8kWh as the specified capacity (Full pack when new) or from about 2021 82kWh.
AlanSubie4Life
Efficiency Obsessed Member
This is now just ridiculous. You should have your own thread! I am also very curious how much energy you can actually extract from this pack!
You do have to use the energy app calc, or a variety of other equivalent methods (there are about 3-4 other ways) to determine that energy content per displayed mile, however. (Or gather it from this forum, or SMT, or whatever.)
(And yes there were a couple of errors in @STS-134 ’s description (should say multiply, and also before that multiply have to multiply by 0.955)).
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UncertainTimes
Active Member
Why overthink this. Charge to 69% all day everyday. Whether you’re using the top half or bottom half, you’re having fun either way.
cmy4x4
Member
Release notes for version 2022.36.2 Downloading now.
Tesla's Service Mode now contains a battery section that allows you to view the vehicle's high-voltage battery health and perform 'Health Test.
Tesla's Service Mode now contains a battery section that allows you to view the vehicle's high-voltage battery health and perform 'Health Test.
aerodyne
2 of 3 EV's - Defect Free!
I have used the low SOC during non use to keep the calendar aging low. Earlier my job was ~50km away so a regular jobday was starting at 55% after the charging just was finished, driving 50km and efter work home plus often a couple of smaller drives during the evening. During night standing with about 15-30%. Now I have 240km to work
But work on week each work period. Bigger cycles but the car is parked with low SOC during those weeks.
But I did a lot of other travel as well, needing higer SOC. I also have quite a few 100% charges to check for example the Nominal Full Pack etc. The number of full charges is 25-30 (25 according to teslafi but I had some before I did get teslafi)
The number of Supercharging sessions is about 43 or so (37 in Teslafi plus some before I got teslafi). In total about 18% of all energy is Supercharging.
Yesterday I had a NFP of 78.1kWh / 491km range, after 52.000km and 22 months.
My NFP was overestimated by the BMS for a long time, then i drooped and I did see around 3kWh below the probable real value before it crawled up again. Now it is closer to the real value, maybe slightly low (measured 79kWh during a 100-0% drive a few months back).
As calendar aging is the main battery degrador for most people, it is possible to use the upper half of the battery when
needed and still have lower degradation than most other by utilizing low SOC when the car is not in use.
Of course, to win the low degradation competition you should always keep low, use very small cycles, never charge to 100%.
But otherwise you dont need to always use the lower half of the battery as one might think reading the heading of the thread.
But work on week each work period. Bigger cycles but the car is parked with low SOC during those weeks.
But I did a lot of other travel as well, needing higer SOC. I also have quite a few 100% charges to check for example the Nominal Full Pack etc. The number of full charges is 25-30 (25 according to teslafi but I had some before I did get teslafi)
The number of Supercharging sessions is about 43 or so (37 in Teslafi plus some before I got teslafi). In total about 18% of all energy is Supercharging.
Yesterday I had a NFP of 78.1kWh / 491km range, after 52.000km and 22 months.
My NFP was overestimated by the BMS for a long time, then i drooped and I did see around 3kWh below the probable real value before it crawled up again. Now it is closer to the real value, maybe slightly low (measured 79kWh during a 100-0% drive a few months back).
As calendar aging is the main battery degrador for most people, it is possible to use the upper half of the battery when
needed and still have lower degradation than most other by utilizing low SOC when the car is not in use.
Of course, to win the low degradation competition you should always keep low, use very small cycles, never charge to 100%.
But otherwise you dont need to always use the lower half of the battery as one might think reading the heading of the thread.
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