Glass in Cars

Written by Nigel Farrier

There has been a lot of discussion going around about how the glass roofs on cars cause the car to get too hot making the air conditioning useless. Also people wonder about getting sunburnt through the glass roof.

As a (retired) medical practitioner as a skin cancer specialist and a scientist I can answer all these questions and more.

1 Ultraviolet light.

Lets first discuss UV radiation. There are basically 3 types of UV – UVA, UVB and UVC. The latter is the most damaging of all. UV light is one the electromagnetic spectrum with shorter wavelengths than visible light. UVA is the closest to visible light.

Fortunately UVC, whilst being the most damaging, is completely absorbed by the atmosphere so none ever reaches our skin. UVB is the middle group and is the one that causes sunburn. UVA has the longer wavelength and is assocaited with skin aging.

So what about glass? Remember that not all glass is equal so this is a generalisation. Glass is designed to let light through so UVA, being closest to the visible spectrum, can penetrate glass but only about 60% actually gets through. Fortunately UVB is totally absorbed by glass.

Glass fitted to the front windscreen of cars lets through UVA as above. A lot of side windows are slightly tinted in modern cars so a much larger proportion of the UVA is absorbed. Roof glass, certainly on the Teslas, is coated with a variety of filters that blocks most of the UV light. According to Tesla the roof absorbs at least 99% of all UV radiation. So it will not cause sunburn and little to no skin aging. You would have to sit in your car in bright sunshine constantly for at least 100 days to get the same UV dose as standing out in the sun for 1 day. Quite insignificant.

2 Infrared light.

At the other end of the visible spectrum is red and beyond that infrared and just as UV is divided into 3 bands so is infrared. Unfortunately is is not named as easily as UV but near, middle and far infrared. Near IR is the closest to visible red.

So does IR get through glass? Well once agin the answer is that depends. IR is a form of light, not heat. The heat is transferred by molecules vibrating.

So as before the near IR wavelengths are let through by glass as they are closest to the visible bands. The energy from near IR is too large to excite atoms in molecules from vibrating.

The middle band of IR is often referred to as thermal IR. This band will cause molecules to vibrate and ‘heat’ up (actually generate heat). This radiation is strongly absorbed by matter (glass in this case) so does not get through. But it will heat up the glass. Far IR is the same although has a lower energy state.

The glass on Tesla motor vehicle roofs has several coatings to absorb a lot of this energy before it enters the cabin. As already stated virtually no UV gets into the cabin and the IR is absorbed by the coatings and the glass in the roof. This does cause it to heat up which can then radiate that heat into the cabin (and out into the atmosphere as well).

As an interesting experiment try using an infrared camera to look at items through a glass window. You wont get a very clear picture at all even with the IR LEDs that a lot of security cameras have.

So there we have it. Certainly do not panic about the UV radiation through the glass roof. With regard to the infrared yes it will slowly heat up the glass and then the interior of the car. So does a metal roof. It heats up in the sun and radiates the heat into the car and the car heats up.

So what can we do to prevent this? Most people rush out and buy shades for the roof, put on tinting and so on. Lets cover these ‘solutions’.

Window tinting – from an aesthetic point of view a lot of people really like tinted windows and I can understand that. But it does not make much difference to the IR heating up the windows which then gets radiated into the cabin. It also make ZERO difference to the amount of UV getting in in modern cars. If you want window tinting that’s fine. Do it.

Roof tinting – there was some problems in the early days of putting the tinting on the inside of the roof causing the roof glass to crack. That may have been solved now but personally I am still hesitant about putting tinting on the inside. The glass roof still gets hot.

There is a ceramic coating that can reflect some of the IR light and this is put on the outside and probably helps a bit but it needs to be replaced after some years.

The Tesla glass roof already has at least 3 layers of coating on it to prevent a lot of the problems (hence the problem that some people think the roof is rusting due to an orange hue it got).

Inside roof shades – these are similar to the windscreen shades that a lot of people use. They still dont stop the roof glass from getting hot and several makes actually impede the view from the rear windscreen as they hang down at the back.

What is the answer then? Here are my tips for an enjoyable experience in your Tesla.

Firstly leave the air conditioning on when you leave the car in the sun. You have almost certainly used it whilst driving to where ever you needed to go so it has already done its job of cooling down the interior. For it to keep the interior at that temperature it will use less energy to maintain it than it does to get it down to that temperature.

This is a really great idea if you are parked up at a charger and plugged in as the power from the charger is used to keep the car cool rather than the battery pack providing you are not plugged in to a 10amp socket as the air conditioning may need more power than that can provide so some battery use may happen.

If you are leaving your vehicle parked always try and put it in the shade with or without leaving the air conditioning running,

If you are leaving your vehicle parked for quite a while (and its in the shade) you can leave the air conditioning set to keep the cabin below about 40 degrees C using the cabin overheat protection mode.

Still dont want to do any of this? Why not just turn on the air conditioning from your Tesla app on your phone giving it enough time to cool the cabin for your arrival?

None of these will work once the battery state of charge falls to below 20% (neither will sentry mode).

Whilst on this subject of air conditioning I would also like to cover some of the misunderstandings regarding what is in a Tesla. I must admit for the first few months of ownership I was convinced the air con was not very good until I found out a few things (such as leave it running).

During the hot weather I have mine set at about 22.5 deg C and on AUTO (experiment to find your own preferred settings). It works fine. You wont feel a blast of cold air on your face as in other vehicles as they have small outlets that can be directed at your face. Teslas don’t do that. You can direct the vents towards you but you wont feel it and this is why a lot of people say the air con is useless. Its not. The cabin gets down to its temperature very efficiently and the fan (when on auto) slows down.

I leave mine set to auto and let the car take care of the interior itself. You have just been used to something different and therefore feel its not as good. It is.

In summary then. You wont get sunburnt from the UV. The roof glass will get hot so don’t keep touching it. Try touching the metal roof of any car that is out in the sun. You will burn your hand just the same. Tint the windows if you want to for aesthetic reasons (and it may decrease slightly the UVA getting in through the side windows). Before you go out and spend a lot of money of roof tinting, shades etc before you have taken delivery (I know several people that do this) just try it out first.

I sit with my completely bald head only 2 inches from the roof and even in the 40 degree heat we get here I do not feel the need for anything except my cars air con.

Explaining the Nullarbor EV Chargers

As you may have seen in recent news retired engineer Jon Edwards has designed, built and installed a Biofil DC charger at Caiguna on the Western side of the 1200km drive between Ceduna and Norseman, this provides a handy boost for the adventurous EV owners crossing the Nullarbor when border openings allow. Before I continue let’s make one thing very clear, you’re under no obligation to drive across the Nullarbor, commercial air travel is faster, safer and probably cheaper, but as Ferris said “Life moves pretty fast, if you don’t stop and look around once in a while you could miss it”.

Below I’ll discuss the charging available at the locations that are spaced evenly apart.

Before attempting to drive an EV across this part of Australia remember that Plugshare is the only app with the accuracy to plan charging stops, also don’t rely on apps to predict your energy consumption and arrival times, the road surface and wind direction plays a major part in how far you’ll get on a charge, play it safe and always plan to arrive with at least 30kms of range remaining. If you wisely plan your daytime and overnight charging stops the less time you’ll spend topping up the batteries.

Balladonia 22kw CCS2 DC charger

Departing Norseman and driving East the first well spaced charging stop is at the Balladonia Roadhouse, 190kms from Norseman, which has a 22kw CCS2 DC charger plugged into the 32amp 3 phase outlet. Compared to the latest 250-350kw DC chargers popping up close to Australia’s populated areas 22kw appears prehistoric, but in reality they’re a pretty handy short term solution that doubles the charging speed a model 3 can get from the existing 3 phase outlet and better still triple the charging speed available to a Hyundai Kona.

Caiguna, 181kms drive from Balladonia, has a 50kw DC charger powered by a Biofil generator, politely ask the counter staff to start the charger then go and enjoy the air conditioned Cafe.

Madura 22kw CCS2 DC charger

Madura, 157kms drive from Caiguna, has a 22kw DC charger plugged into the 32amp 3 phase outlet, payment is a donation to the Royal Flying Doctor Service tin located in the dining area. Note: as at April 2024 not available due to plug issue.

Mundrabilla, 116kms from Madura and 81kms from Border Villa, now has a 22kw CCS2 DC charger plugged into the 32amp 3 phase outlet. Note: as at April 2024 3 phase only available.

Eucla, this location is 182kms east of Madura, charging is via a 32amp 3 phase outlet in the Laundry of the Eucla Motor Hotel. Be aware that this outlet is not available between 9.00am and 3.00pm, if you expect to arrive at this time maybe use the Border Village charge point, 12kms to the East. Note: this location is no longer available for EV charging.

Nullarbor Roadhouse 32amp 3 phase

Nullarbor Roadhouse, 197kms drive from Eucla, has a 22kw CCS2 DC charger plugged into the 32amp 3 phase outlet at the rear of the building close to the motel units. Note: April 2024 NRMA DC charger now in place.

Penong Caravan Park, 223kms east of the Nullarbor Roadhouse, has a 32amp 3 phase (it has been prone to tripping at 28amps so plan accordingly). Penong is part of the South Australian grid so is likely to get a reasonable speed DC charger before too long.

Cocklebiddy and Border Village also have handy 32amp 3 phase outlets if you want to shorten the driving distances between charge sessions or wish to try different accommodation on the return journey.

“The Electric Highway. Plugging the gap!”

This is the latest video from Tesla owner and TOCWA committee member Steve Rogers.

Driving across the Nullarbor can be fun the first time, but requires a huge amount of patience on subsequent trips. An alternative is putting your car on a train to Adelaide and continuing your journey from there.

Currently the journey in EV requires longer stops on AC charging only, this is soon set to change, check out this video to see why.

If you would like to donate to The Big Lap has Gaps fundraiser you can find the link here. If you are not able to donate please share.

December Casual Meetup – Good Company

Our next casual meetup is Sunday 5 December 2021 at 11:00am at:

Good Company Bar, West Deck, Karryinyup Shopping Centre

https://www.goodcompanybar.com.au/

Casual meetups are open to everyone including those who have never seen a Tesla before.

It’s an ideal opportunity to meet club members and to see the cars in the flesh which we are all passionate about.

It’s also a great way for new owners to learn more about their cars and to share in the vast pool of knowledge gained by other members.

We hope to see you there and look forward to chatting about all things Tesla.

Tesla Model 3 Economics Compared to an Average Australian Petrol Car

Pete Petrovsky 26 Nov 2021

One of the comments that gets the most eyebrow-raising reactions when talking about Tesla cars, is the fact that, for most owners, a Model 3 works out considerably cheaper than an average Australian car. Although some people are beginning to understand that an electric vehicle (EV) is less expensive to run than an internal combustion engine (ICE) vehicle equivalent, it’s hard to come across a non-EV owner who isn’t surprised to learn that, if all major costs associated with owning a car are included, a Model 3 Rear Wheel Drive (formerly known as the Standard Range Plus) works out thousands of dollars cheaper over just a short three-year period of ownership.

I like to explain this with a second-person hypothetical. Let’s assume that you decide to buy a Model 3 Rear Wheel Drive (RWD) today and your neighbour also buys a vehicle on the same day, but instead they choose an average Australian car, something along the lines of an average Ford, Toyota, Volkswagen, Nissan, Subaru, Honda or similar. The longer the ownership period the more favourable the outcome for the Model 3, and even thought the average Australian car is more than 10 and a half years old, let’s assume that both you and your neighbour sell your cars after just three years. If we take into account all significant costs, including the upfront drive away cost, a.k.a. the sticker price, and if we include depreciation, fuel costs, maintenance, insurance as well as registration and licencing fees, after all is said and done, you will be left with almost $14,000 more in your bank account than your neighbour who bought the average Australian petrol or diesel car. That’s a substantial amount of money, it’s enough to buy a second new car. Many people are either astounded by this or they simply don’t believe the figures. I have therefore provided a summary table of my calculations, below.

Tesla Model 3 RWD versus average ICE car total cost of ownership table

As with all calculations, the devil is often in the detail and assumptions can make or break even the most robust models. Where possible, I have therefore, tried to only use robust figures from reputable sources which I can readily substantiate. For example, as the Model 3 has only been in Australia for a little over two years and with the current resale values being elevated by unique market dynamics stemming from the Covid-19 pandemic, I have based the depreciation rates on the iSeeCars.com study which analysed 5.7 million new cars bought in the united states between January and June of 2017 and 1.2 million cars from the same model year sold between January and June in 2020. I have tested the model to the sensitivity of the inputs and, interestingly, even if we were to halve the depreciation rate used for the Model 3, while keeping the depreciation rate for the average ICE car unchanged, the Tesla would still come out more than $7,000 ahead.

I have also used Australian unleaded petrol prices averaged over a 10-year period from 2011 to 2020 inclusive, however, rather than using average Australian electricity prices for the same period, I have simply used the latest (and also the highest) average Australian tariffs even though, as most electric vehicle owners know, there are several EV friendly tariff plans available to EV owners. Furthermore, as is the case with many EV owners, the cars can be charged using electricity produced by solar photovoltaic (PV) systems. Once the solar PV system has paid for itself, it can effectively provide free electricity for its owners who mostly either charge at home or at convenient destination chargers such as those located in shopping centres which are generally complimentary. It is, therefore, not impossible to fuel an EV at virtually zero cost.

For the servicing and maintenance costs, I have used prices sourced directly from Tesla, but I have used average logbook service costs which include capped-price service schemes as well as prices taken from lower-cost third-party service centres. For more information, please see the video below which reveals that the Model 3 costs about a third as much to service over a 5-year period than the cost of a single service for an average Australian car. In other words, it costs less to service the Model 3 over a three-year period than an average Australian internal combustion engine (ICE) car over six months.

Although, I have been conservative with the inputs in the calculations, with the Model 3 RWD (nee SR+) starting at a drive-away price of $63,626 as an average across all the states in Australia, versus approximately $40,912 for an average new Australian car, one could argue the analysis ignores the additional finance costs. As the table below shows, however, even after factoring in finance costs, the Model 3 still comes in $12,617 ahead of an average Australian internal combustion engine car.

Total cost of ownership comparison table

Whether it’s $12,617 or $13,679, either way, it is a relatively large sum of money, as I have mentioned, it’s enough to pay for a second new car, but amazingly this is not where the savings stop. You may have noticed, there is one category, namely insurance, where the Model 3 is more expensive. That said, while insuring a Tesla may be more expensive in absolute terms, mainly due to the higher car value, personally, I have found the premiums cheaper relative to the insured value of the vehicle and the Australian average figures seem to be roughly on par in this respect with the annual premiums accounting for between 3–4% of both of the cars’ drive-away price.

Interestingly, however, this is one of the areas where Tesla continues to innovate. Two years ago, Tesla introduced its own insurance product in California, named Tesla Insurance. As Tesla begins to slowly roll out the product across other US states, the company is pairing the policies with its Safety Score telematics which, as the name suggests, provide the driver with a safety score based on their driving behaviour which is designed to statistically predict the likelihood of a future collision. Tesla bases the monthly insurance premiums on each driver’s Safety Score, and as the score changes the insurance premiums also change from month to month. Tesla calls this Real-Time Insurance. Naturally, the higher the safety score the lower the premiums. For example, there can be more than a 56% premium discount based on a 98% versus an 88% Safety Score. It remains to be seen when Tesla introduces the Safety Score to Australia or when Tesla enters the Australian car insurance market but when it does it will make the economics of the Model 3 even more compelling not only for new owners but also for existing ones.

The only other area where a Tesla Model 3 is more expensive than an average internal combustion engine or ICE car is the upfront cost or the sticker price. This is where state and federal governments should play their part, it’s crazy that we’re still subsidising fossil fuels while taxing electric vehicles.

Model 3 RWD on-road taxes, fees and chargers by state in Australia

That said, Tesla is working on a US$25,000 model commonly referred to as the ‘Model 2’ but Elon Musk has already confirmed this won’t be the car’s name, perhaps it may end up being named the ‘Model A’. Once it is unveiled and when it eventually goes on sale in Australia, it may retail below or roughly at around the price of an average petrol or diesel car thereby not only putting the economics of an entry-level Tesla even further beyond any question, but it will inevitably become the final death blow to the internal combustion engine as a means of powering a daily commuter.

It is fairly amazing that the Model 3 has economics which are superior to an average Australian car because implicit is the assumption that the two are a like-for-like comparison when, in reality, nothing could be further from the truth.

The fact is that a Tesla Model 3 is superior to an average internal combustion engine vehicle in pretty much all aspects including:

Furthermore, unlike most cars which are the best they will ever be the day they are driven off the dealership lot, the Model 3 continually improves via mostly free over-the-air (OTA) software updates.

The impressive yet not exhaustive list below outlines just some of the additional features which have been added to my Model 3 since I bought it a little over two years ago:

  • a boost of approximately 5km more range,
  • approximately 5% more power,
  • single pedal driving,
  • dog mode,
  • camp mode,
  • side camera video feeds,
  • Netflix,
  • YouTube,
  • a long list of new voice commands including voice keyboard,
  • ability to have incoming SMS messages read out and the ability to dictate a response,
  • driving visualisation updates including displaying humans, stop signs, traffic lights and even objects such as traffic cones or witches hats, rubbish bins, traffic barriers and so on,
  • automatically save dashcam footage on honk,
  • ‘Caraoke’ and a raft of new video games,
  • driver profiles,
  • ability to adjust the charging rate via the app,
  • app customisation,
  • car-wash mode,
  • Smart Summon which enables the car to drive itself from up to 50–60 metres away in a car park,
  • and a raft of driver assistance and Autopilot improvements such as the ability to monitor the speed of traffic in surrounding lanes and, if required, overtake other cars. The car can also stop on traffic lights, stop signs, roundabouts and so on.

These are just some of the additional features added over the last 2 years, but it doesn’t stop there, as innovation and improvement seem to be a continual ongoing process at Tesla. There are many new exciting updates on their way including the Full Self-Driving (FSD) capability beta button, the Safety Score beta, the FSD subscription service, the ability to detect wet road conditions, remote live sentry view, in-car purchases and these are just some of the upcoming features we currently know about. I’m sure there are dozens of more improvements in the pipeline which we are yet to find out about.

Furthermore, this is just what I either happened to notice or read about in the software release notes, but the car has also been improving its already unmatched safety with undocumented updates like safer airbag deployments adjusting for occupants’ weight and seating position. In other words, the airbags now adjust when, how fast and in what direction they deploy depending on where on the seat the driver is sitting. The algorithm also considers the pressure distribution on the car seat to determine if the passenger is a baby, a toddler or an adult and it even tries to calculate the probability of a person’s gender.

In addition to the over-the-air updates, the cars are equipped with all the hardware necessary to enable full self-driving (FSD) in the not-too-distant future. One could argue that this makes the cars themselves but perhaps also the economics largely future proof. Perhaps this and the potential that FSD may one day be worth US$100,000 is an important factor contributing to the Model 3 showing a depreciation rate that is 25% lower than an average car.

Does this mean that a Model 3 or a Tesla for that matter is the right EV or even the right car for everyone and for every situation? No, of course not, but taking into account FSD improvements, in the majority of situations, the Model 3 and Model Y superiority, not only in economic terms but also in terms of both the quantitative and the qualitative value they offer their owners, makes one wonder if we haven’t already reached the point which Elon Musk referred to when he compared driving anything other than a Tesla to owning a horse or as he further elaborated, it is “financially insane to buy anything other than a Tesla”.

Pete Petrovsky

Pete Petrovsky is an active TOCWA (Tesla Owners Club of Western Australia) committee member and a long-time EV enthusiast. He placed a $6,000 deposit for a Model X (#39) in 2014 but when it came to taking delivery he couldn’t justify the cost, so instead, he and his wife decided to buy two PHEVs and wait for the Model 3. In March of 2016 they bought the Holden Volt and a couple of weeks later the Mitsubishi Outlander PHEV, and on the day it was unveiled, Pete ordered the Model 3. After selling the Outlander, in September 2019, Pete took delivery of the Model 3 and despite still loving their Volt, Pete and his wife are now looking forward to ordering the Model Y as soon as it becomes available in Australia.

When he gets time, Pete posts videos on his ‘Tesla Ahead of the Curve’ YouTube channel. He is a long-term Tesla shareholder and over the last eleven years has been responsible for more commercial rooftop solar PV in Perth than any other individual. In 2016 Pete added grid electricity to his role and since October 2020 he has been Managing Director of Imppact Energy Consultancy. In July of 2011, Pete also installed one of the first ‘oversized’ 6KW solar PV systems in Perth, which to this day continues to power their home and both EVs with free sustainable energy.

TOCWA 2021 AGM

The Tesla Owners Club of Western Australia 2021 Annual General Meeting was held today at the Newport Hotel in Fremantle. The Committee was increased by 2 taking it to 9 through to the next AGM in late November 2022. Those Committee members are:

  • Nigel Farrier and Steve Rogers (Newly elected until November 2023)
  • Rob Dean, Martin Kane and Rodney Louden (re-elected until November 2023)
  • Andrew Harvey, Harald Murphy, Peter Petrovsky and Ken Taylor move into year two of their elected term that ends in November 2022.

In the 12 months up until today’s AGM TOCWA held 19 in person events organised directly by TOCWA plus attended at least 11 other events as guests. TOCWA Secretary Harald Murphy conducted 47 Ask Us Anything Zoom sessions on Wednesday evenings totalling over 150 hours of content.

The Tesla Owners Club of Western Australia increased its official membership to 377, up from 142 at the same time last year. This represents approximately 25% of Tesla owners in WA, the average across the 172 official Tesla Owners Club worldwide is 11%.

Thanks to those who attended.

If you would like to become a TOCWA member click here.

TOCWA has No Time To Die

Thanks to committee member Pete Petrovsky, Tesla Owners Club of Western Australia (TOCWA) have secured priority parking at Perth’s last remaining drive-In theatre for No Time To Die, the latest James Bond movie which will be released soon.

To secure the best spots and to be among other Teslas, you will need to make a free booking at the link below:

https://www.trybooking.com/BVNGD

TOCWA priority booking is free and the movie entry is only $22 per car which is paid on arrival.

PLEASE NOTE: Only make one booking per car attending.

Date:                    Tuesday 23 November 2021

Time:                    5:15pm for the best spots, 5:45 for 2nd best and 6:15 for general admission

Venue:                 Galaxy Drive In Theatre

Address:              157-167 Goollelal Drive, Kingsley WA 6026

Food:                    The onsite cafe sells Homemade Burgers, Hot Dogs, Hot Chips, Ham + Cheese Toasties, Nuggets & Chips, Chiko Rolls, Confectionary, Milkshakes, Soft Drinks etc.   BYO stronger drinks.

November Casual Meetup

Our next casual meetup is Wednesday 3 November 2021 at 6:30pm at:

7 Mile Bar & Bistro,

501 Wanneroo Road, Balcatta

https://7milebar.com.au/

Casual meetups are open to everyone including those who have never seen a Tesla before.

It’s an ideal opportunity to meet club members and to see the cars in the flesh which we are all passionate about.

It’s also a great way for new owners to learn more about their cars and to share in the vast pool of knowledge gained by other members.

We hope to see you there and look forward to chatting about all things Tesla.

Enhanced Autopilot

In other markets, Tesla offers “Enhanced Autopilot” as an option below “Full Self Driving”. This option offers Nav on Autopilot, Auto lane change, Autopark and Smart summon for approximately half the cost.

Full Self Driving then adds Traffic Light and Stop Sign control on top.

A screentshot of the UK order page for Enhanced Autopilot

If this option were offered in Australia, for those that have not purchased FSD, would you buy Enhanced Autopilot?

We’d love to get your feedback via the poll on our Facebook page linked below – or feel free to comment on this post.

https://www.facebook.com/groups/1627907424194896/posts/2993552684297023

100% a Waste of Time: Why charging to 100% is defeating the purpose of Superchargers

Pete Petrovsky 21/10/2021

Supercharging Karrinyup

As most EV owners will know, there are two main ways to charge an EV, AC or DC, but there’s also another less known and slightly more nuanced distinction.

A charger’s main purpose can be for rapid top ups or for longer perhaps even overnight charging and it’s important for EV drivers to understand this difference as it will not only save a lot of time, but it will also result in a better ownership experience for the entire EV community.

The main purpose of ultra-rapid DC chargers such as the Tesla Superchargers is rapid top-ups to facilitate convenient travel between built-up areas. This is critical in winning over the broader driving public who have concerns about charging downtime on long trips away from home. The problem is many new owners have misunderstood this and are in fact wasting a lot of their time charging at high battery percentages. How much time are they wasting? It depends on the vehicle’s next destination but as can be seen from the graphics below, it’s more than many drivers realise.

Test conducted with a Tesla Model 3 Performance charging from a V3 Tesla Supercharger at a 14-degree outside temperature with a pre-conditioned battery.

As the chart above shows, a long-range battery takes about the same time, roughly 14 minutes, to charge from 10% to 60% as it does to charge from 90 to 100%. In other words, you can spend the same 14 minutes topping up 50% at a lower state of charge (SoC) or 10% at a higher SoC. 

50-60% SoC is a key level because not only does the time to charge each 5% increment begin to lengthen to charging speeds attainable at slower (non-ultra-rapid) DC chargers but generally it’s enough battery capacity to cover the distance between Superchargers on long road trips.

What is not illustrated on the graph is what happens once the state of charge reaches 100%. Once at 100%, the charge time jumps off the chart as it took me at least a further 19 minutes of trickle charging the last few watt hours and balancing the cells before I lost patience and quit the test.

TezLab power chart.

As can be seen in the graphic above, at roughly around a 14% state of charge (SoC) the car reached its peak charge of 244kW but then this began to taper off down to 192kW at 30% SoC, then to 110kW at 50%, 81kW at 70% and 42kW at 90% before dwindling down to 5kW once it remained at 100% for almost 20 minutes.

Once at 100%, the time the car takes to completely finish charging is dependent on how long it has been since the battery was fully charged to 100%. The longer the period between full charges the longer it takes to balance the cell groups and the longer the battery takes its time at the 100% level.

Powered by a lithium-nickel-cobalt-aluminium (NCA) battery chemistry, once at 90% or above, it is best to begin driving the Model 3 Performance (and Long Range) to ensure minimum long-term battery degradation. It’s not ideal to keep this chemistry above 90% or below 20% for extended periods of time. In fact, the above 90% charge level should be reserved only for times, when necessary, on longer stretches between chargers on country road trips. However, that said, it is also a good idea to balance the cells once every 3-6 months. The added benefit is that the battery management system (BMS) will also get a chance to recalibrate itself to ensure accurate battery range readings.

In contrast, it is ideal to charge the lithium-iron-phosphate (LFP) battery chemistries, found in the Shanghai built and soon also in the Fremont built Standard Range Plus Model 3s, to 100% at least once a week and it’s also perfectly fine to charge to 100% on a daily basis.

Irrespective of the battery chemistry, however, to save wasting your time at Superchargers and unnecessarily taking up this important infrastructure, please be mindful of how busy the charger is. If you feel the need to charge to 100% and if you have plenty of time, during off-peak times when Superchargers are hardly used, it is perfectly fine to squeeze in every last watt but at busy times, vehicles taking up much needed charge bays while charging at a fifth or less of the charger’s potential is a burden on the infrastructure and not helpful to fellow EV owners.

243kW charge rate.

Therefore, please consider only charging to a lower percentage and leaving the charging at the top state of charge levels for your home, BNB, or at overnight AC destination chargers such as those allocated to your room at hotels and EV-friendly resorts. You’ll only be doing yourself, your EV community and even potential new EV owners a big favour.

P.S. Special thanks to TOCWA Chairman Rob Dean for not only helping with this article but also for coming up with the idea for the test.