Drew57
Active ember
I recall reading somewhere that the Taycan has a more efficient regen method & it sends up to 270kWh back into the battery compared to 75kWh max (?) in a Tesla.
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Estimated Battery Degradation - Model 3
- Thread starter pdk42
- Start date
Glan gluaisne
Active Member
How much power (and I guess you mean power, kW, rather than energy, kWh) gets recovered in regen is very largely a function of how severe a regen braking effect is acceptable. I had regen set to a high level on my electric motorcycle once, and it just made it dangerous, as lifting off even slightly nearly locked up the back wheel. Whilst it might be possible to increase the regen on the AWD Tesla's, I suspect the limit for the RWD models is safety, and the maximum braking force that is safe and stable at the rear wheels.
Front wheel drive EVs have a big advantage here, as they can have much more aggressive regen, due to the increased braking effect that's acceptable at the front wheels (often the rear brakes do little more than help keep the car straight when braking). I'm not sure whether there's a difference between the AWD Teslas versus the RWD models, but in theory it should be possible to significantly increase regen with AWD, both because the front wheel regen can be increased a lot and because the system should be able to dynamically control the front/rear regen brake bias.
I'm also bit concerned with battery attrition in my LR AWD.
It says 265 miles on 89% charge!! So my 100% would be only 297 miles.
15K miles, 11 months old. Almost always charged with home 7kw chargepoint
Charged in SuC only about 5 times and charged to 100% on these 5 occasions only.
Should I be contacting Tesla?
It says 265 miles on 89% charge!! So my 100% would be only 297 miles.
15K miles, 11 months old. Almost always charged with home 7kw chargepoint
Charged in SuC only about 5 times and charged to 100% on these 5 occasions only.
Should I be contacting Tesla?
Glan gluaisne
Active Member
As mentioned earlier in this thread, the car's systems can only make a very rough guess at range remaining, based on how the car has been driven historically. In order to match the specification range, just as with MPG in a conventional car, someone would need to drive exactly the same acceleration, deceleration and speed profile, with the same range of gradients, and at exactly the same air temperature and density. In practice, no one is ever likely to drive like this, so the range will always vary from the spec.
This is exactly the same as with any petrol or diesel car, virtually no one ever gets the stated range from a tank of fuel, as determined by the advertised MPG and fuel tank capacity. We're used to seeing cars advertised as doing 60mpg, for example, giving a range of about 528 miles from a 40 litre tank, but finding that, in reality, the best we can get is about 440 miles from a tankful, because the real world fuel consumption is only around 50mpg. EVs are no different at all, range is impacted by exactly the same things that impact range on any vehicle, primarily driving style, speed, terrain, temperature and air density.
Jason71
Well-Known Member
At 13K mine is about the same as yours and I have only superchargered about 5 times as well and never to 100%
There is often reported to be an initial drop-off like this in the first year that then stabilises or as other have said it may just be the BMS.
I'm not concerned.
Glan gluaisne
Active Member
I just don't get this sensitivity to apparent range at all. Most people buy a petrol or diesel car and accept that it's lost anything from 10% to 30% of its advertised range as soon as they take delivery. Very few such cars ever come close to their advertised range. Why should we expect EVs to be different?
For example, my wife bought a new Yaris Hybrid a few years ago. It was advertised as having a range of ~674 miles. The very best range she has ever been able to get out of it has been about 550 miles and most of the time the range is only around 475 miles. In range percentage terms, the very best she's managed is about 81% of the advertised range, and most of the time she only gets about 70% of the advertised range.
This isn't unusual, pretty much every car ever sold fails to live up to its specified range figure. If anything, Tesla's seem to be quite remarkable in getting far, far closer to the advertised range than the majority of other cars.
For example, my wife bought a new Yaris Hybrid a few years ago. It was advertised as having a range of ~674 miles. The very best range she has ever been able to get out of it has been about 550 miles and most of the time the range is only around 475 miles. In range percentage terms, the very best she's managed is about 81% of the advertised range, and most of the time she only gets about 70% of the advertised range.
This isn't unusual, pretty much every car ever sold fails to live up to its specified range figure. If anything, Tesla's seem to be quite remarkable in getting far, far closer to the advertised range than the majority of other cars.
Too much information can be a bad thing.
I changed my readout to percentage and never looked back. I don’t see the point of using miles as a guideline since you’re using an absolute measurement that will not necessarily track with actual traveled distance, as it will depend on a variety of conditions and driving style.
With percentage I have a reasonable idea of when I should be heading to a charger, without any risk of me overestimating how far I can go. Plus it avoids all this incessant obsession over degradation. The car has an 8 year battery warranty, and people have owned the cars a fraction of that time. In several years if you think it has actually degraded take it up with Tesla. Until then, chill!
Jason71
Well-Known Member
Its useful to know the remaining miles on a road trip but that is what the energy graphs are for. Percent all the wayToo much information can be a bad thing.
I changed my readout to percentage and never looked back. I don’t see the point of using miles as a guideline since you’re using an absolute measurement that will not necessarily track with actual traveled distance, as it will depend on a variety of conditions and driving style.
With percentage I have a reasonable idea of when I should be heading to a charger, without any risk of me overestimating how far I can go. Plus it avoids all this incessant obsession over degradation. The car has an 8 year battery warranty, and people have owned the cars a fraction of that time. In several years if you think it has actually degraded take it up with Tesla. Until then, chill!
Glan gluaisne
Active Member
I well remember the first car I had with an onboard "computer", a Jaguar XJ-S. One of the display options was remaining range. You could easily knock 50 miles off the range in a few seconds of spirited driving, only to see the range magically increase if going downhill. The principle that car used to derive range wasn't a lot different to the way that the Tesla does it. It measured consumption on the fly, using the fuel injection pulse width, in the same way as the Tesla measures power on the fly, from current and voltage. From that, and information from the vehicle speed sensor it tried to estimate the rate at which fuel was being used, in the same way as the Tesla measures battery energy that's being used.
The XJ-S used to be reasonably good at estimating range by the time most of the tank(s) of fuel had been used, and in the same way the Tesla system is reasonably good at estimating range by the time most of the battery capacity has been used. At any other time, any range estimate is bound to be in error, as the car has no way of knowing how it's going to be driven at any future instant. Driving in very cold weather at motorway speeds will use a great deal more energy than driving gently in warm weather, in any car. The car system might try and guess the future, based on the past, but it has no way of knowing if the next drive is going to be a couple hundred miles on the motorway or a couple of hundred miles of gentle driving on B roads.
The XJ-S used to be reasonably good at estimating range by the time most of the tank(s) of fuel had been used, and in the same way the Tesla system is reasonably good at estimating range by the time most of the battery capacity has been used. At any other time, any range estimate is bound to be in error, as the car has no way of knowing how it's going to be driven at any future instant. Driving in very cold weather at motorway speeds will use a great deal more energy than driving gently in warm weather, in any car. The car system might try and guess the future, based on the past, but it has no way of knowing if the next drive is going to be a couple hundred miles on the motorway or a couple of hundred miles of gentle driving on B roads.
That's a very similar graph to what I get from Teslafi for my car. The precipitous drop is rather worrying, but I'm really not sure how much I trust it. It clearly all depends on how the BMS calculates the % and from what I have read there is a lot of potential for uncertainty there. Short of charging to 100% and driving until the car stops it's hard to know how much trust to put in it.
Also - there is a lot of talk on this thread about how the range is affected by driving style. Of course, that's obviously true in one sense, but the Teslafi graph above is calculating it based on the battery's charge accumulation and converting it to "standard" miles using the published Wh/ mile consumption. So previous driving history had nothing to do with that graph.
Glan gluaisne
Active Member
Whilst I believe that what's in that post about allowing the car to better estimate battery capacity is partially true, I'm not convinced that there are permanently connected shunts across every cell group, as it's hard to see what doing this would achieve. There are several ways to do battery management, but one of the most common is to use resistive shunts that are actively switched across cell groups that reach a set voltage threshold. The way this works is that when the battery is being charged, as each cell group reaches the set threshold voltage its shunt is switched on, diverting some of the charge current through the shunt. This allows the cells that have yet to be shunted to receive more current per cell then those that are shunted, so gradually brings all the cell group voltages to the same level.
It doesn't make a lot of sense to have permanently connected resistive shunts across every cell group, as all these would do is cause the pack to discharge all the time. Such an arrangement cannot help the cell groups in the pack balance, as to do that needs a source of charge current (current clearly cannot flow from one cell group to another when the battery pack is open circuit).
Another explanation, and one that matches what's been described, may be that the pack uses active balancing. This can work in several ways, but the one I'm familiar with is the one used on my electric boat battery pack. That uses "flying capacitors", where a capacitor is charged from a cell group, to very close to the cell group open circuit voltage, then switched to the adjacent cell group. If the adjacent cell group has a lower open circuit voltage, then charge is transferred from the capacitor to the cell group. This continues across all cell groups in the pack, until after a period of time the cell groups are each at the same terminal voltage, and the pack is balanced.
The reason that this type of active balancing system fits with the observed behaviour, is that it happens mainly when the pack isn't being charged or discharged. Unlike resistive shunt balancing, that only works during charging, active balancing works when the pack is disconnected, and can take some time to get all the cells to the same state of charge - it's not uncommon for this to take an hour or two, after the pack has been disconnected from the load or charger.
I'm not sure what sort of BMS Tesla use, but the behaviour described fits better with the hypothesis that it's some sort of active system, rather than a purely resistive shunt system. It's quite possible that Tesla may use both methods, with resistive shunt balancing being used during the latter stages of AC charging (this fits with the data, as charge current decreases at the end of a charge) and perhaps active balancing being used to maintain pack health when it's not charged for some time. This is all speculation, as I've not stripped a pack and had a detailed look at the way the BMS works.
It doesn't make a lot of sense to have permanently connected resistive shunts across every cell group, as all these would do is cause the pack to discharge all the time. Such an arrangement cannot help the cell groups in the pack balance, as to do that needs a source of charge current (current clearly cannot flow from one cell group to another when the battery pack is open circuit).
Another explanation, and one that matches what's been described, may be that the pack uses active balancing. This can work in several ways, but the one I'm familiar with is the one used on my electric boat battery pack. That uses "flying capacitors", where a capacitor is charged from a cell group, to very close to the cell group open circuit voltage, then switched to the adjacent cell group. If the adjacent cell group has a lower open circuit voltage, then charge is transferred from the capacitor to the cell group. This continues across all cell groups in the pack, until after a period of time the cell groups are each at the same terminal voltage, and the pack is balanced.
The reason that this type of active balancing system fits with the observed behaviour, is that it happens mainly when the pack isn't being charged or discharged. Unlike resistive shunt balancing, that only works during charging, active balancing works when the pack is disconnected, and can take some time to get all the cells to the same state of charge - it's not uncommon for this to take an hour or two, after the pack has been disconnected from the load or charger.
I'm not sure what sort of BMS Tesla use, but the behaviour described fits better with the hypothesis that it's some sort of active system, rather than a purely resistive shunt system. It's quite possible that Tesla may use both methods, with resistive shunt balancing being used during the latter stages of AC charging (this fits with the data, as charge current decreases at the end of a charge) and perhaps active balancing being used to maintain pack health when it's not charged for some time. This is all speculation, as I've not stripped a pack and had a detailed look at the way the BMS works.
Mr H
Active Member
Why worry at all unless you're keeping the car more than 8 years
I "recovered" my estimated range using this method, but it doesn't last forever. I drive on % display so I only noticed because I saw it on Teslafi...
I've got a P3D- so rated range is set to 310 miles but I believe it's as efficient as a LR in the cruise, and achieving the rated range is doable as long as it's over 5-10 degrees outside.
Couple of rules of thumb that keep you from worrying about range when using % display:
- Target arriving with 15-20% remaining - the car will burn up 5% of that heating the cabin in cold weather
- "Worst case" range is x2 the displayed %'age e.g. 50% = 100 "Worst case" miles
Attachments
I recall seeing an Elon tweet saying that for anyone not happy with any degradation issues but in cases where it’s considered within Tesla’s acceptable range you can pay for the dead cells to be replaced within the pack for new and the cost would be between $3000 and $8000. I thought I screenshotted the tweet so I’ll try and find it.
MrBadger
Badger out
There may be a physical reason for some cars having cliff edge battery 'degradation' graphs
Don't hesitate to report issues to Tesla
Don't hesitate to report issues to Tesla
LongRanger
Active Member
My wife has been very sceptical about the car since it arrived, she loves the punch of the motors but the whole dash and charging thing is not her bag.
Until today, we got back home tonight with something like 59% charge - tomorrow we have to do maybe 30 miles and she glanced at the battery% and said ‘no need to charge tonight, there’s plenty there for tomorrow’.
% is the way forward. I have no idea how many miles the battery thinks it can do or differences in miles range - now we are in colder/wetter weather it’s around 10-25% less efficient (rough eyeball of % battery exhaustion when driving), but expect that will get better in spring. Use it, charge it (hopefully cheaply). Use it again.
Until today, we got back home tonight with something like 59% charge - tomorrow we have to do maybe 30 miles and she glanced at the battery% and said ‘no need to charge tonight, there’s plenty there for tomorrow’.
% is the way forward. I have no idea how many miles the battery thinks it can do or differences in miles range - now we are in colder/wetter weather it’s around 10-25% less efficient (rough eyeball of % battery exhaustion when driving), but expect that will get better in spring. Use it, charge it (hopefully cheaply). Use it again.
Envchem
Member
As suggested I will be using this thread to report how my battery performs. For the guys who haven't read the thread I raised; after a recent SC visit were some electrical parts were replaced, this is my report battery-wise from teslafi:
Looks like a reset on the BMS was also performed; I cant verify this though. I have also checked the range in car display last Sunday when I charged to 100% and it did display as 310. Unfortunately it completely escaped me to take a photo of it; you have to take my word for it. My plan is to charge the car as per norm (daily charge at 90%) and around January do another 100% and see what i get.
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