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.

Around Australia trips in a pure EV

DriverStart/End pointCompletionVehicleNew Usable Capacity
1. Glen GeorgePerthNov 20111956 MG converted Blue32 kWh
2 Richard McNeallSydneySept 2016Tesla S Blue82 kWh
3. Jeff JohnsonSydneyNov 2016Nissan Leaf Blue * 21 kWh
4. Sylvia WilsonGladstoneJuly 2018Tesla S Blue69 kWh
5. Steve & Keita BurrellPerthAug 2018Tesla S Titanium76 kWh
6. Harald MurphyPerthNov 2018
19 days
Tesla X Titanium82 kWh
7. Wiebe WakkerDarwin/SydneyMarch 2019VW converted Blue22 kWh
8. Richard SmithDarwinApril 2019Tesla X White96 kWh
9. Linda RohrsGold CoastJuly 2019 (inc Tasmania)Tesla S Blue96 kWh
10. Rob & Robin DeanPerthNov 2019 (inc Tasmania)Tesla S Blue76 kWh
11. Peter HayesMelbourneDec 2019Tesla 3 Silver72 kWh
12. John PaulMelbourneMarch 2020Tesla 3 Red72 kWh
13. Jules BoagSydneyMay 2021Tesla S White72 kWh
14. Michelle & Terry ArzanikowBallaratJune 2021Tesla 3 White?
15. David McLeodWarnamboolAug 2021Tesla S Blue96 kWh
16. Phil SmithCairns Aug 2021Tesla 3 Blue 72 kWh
17. David CoatesMelbourneSept 2021Tesla 3 Blue72 kWh
18. Bill Gresham & John PhillipsCanberraJuly 2022Hyundai Ioniq Red38 kWh
19. Jeff & Julie WicksGoldcoastJuly 2022Tesla 3 White?
20. Tiff OvertonCentral Coast NSWAug 2022Mercedes EQC400 Silver Grey80 kWh
21. Harald MurphyPerthSept 2022
14 days
Tesla Y White
#AUSYtour
57 kWh
22. Pete PetrovskyPerthSept 2022
17 days
Tesla Y White
#AUSYtour
57 kWh
23. Neil BoltonCanberraOct 2022
17 days
Tesla Y White57 kWh
24. Stuart McBainSydneyNov 2022Tesla 3 White
Charge Around Australia
72 kWh
25. James TaylorPerthDec 2022Tesla 3 White
26,604km
72 kWh
26. David & Lindsay LloydPerthSept 2023Tesla S White96 kWh
27. Harald & Rochelle MurphyPerthSept 2023 (inc Tasmania)Tesla Y White74 kWh
28. Jeff GiddinsJan Juc (Vic)Sept 2023
(towing)
Tesla Y Grey57 kWh
29. Roger & Jenny TruloffGoldcoastNov 2023Tesla 3 White72 kWh
30. Richard Laxton & Myuu KumagaiMelbourneNov 2023Tesla 3 Blue72kWh
31. Harald MurphyPerthNov 2023
10 days
Tesla Y White74kWh
32. Shane Parker & Sarah WhitePerthFeb 2024
(1st caravan/accomm being towed)
Tesla 3 White52kWh
33. Harald MurphyPerthFeb 2024 – Figure 8Tesla Y White74kWh
34. Warwick ParkinsonBrisbaneApril 2024Tesla 354kWh
35. Trent Nikolic & Dominic WisemanSydneyMay 2024KIA EV9 Grey99kWh
36. Louis ChristosPerthJune 2024BYD Seal Grey82kWh
37. RT VandaCoorooman (Qld)August 2024Tesla 3 Blue72kWh
38. Sue & Peter
Gosney
MelbourneSept 2024 with dogs
Ruskin & Oliver
Tesla 3 Grey75kWh
39. Harald MurphyPerthSept 2024 – Figure 8 Towing 19 daysTesla Y White 74kWh
40. Rainer Zietlow & Marius BielaSydneySept 2024VW ID.4 White77kWh
41. Stan GortonKangaroo Island (SA)October 2024 with TwiggyPolestar 2 White75kWh
42. Tim Devereaux

42. Jon Edwards
Harvey (WA)


Perth
October 2024

October 2024 1st Truck
Hyundai Kona White
Hyundai Mighty Truck
64kWh

115kWh
44. David & KrishnaPerthOctober 2024Hyundai Kona White64kWh
45. Ben BeverleyHervey Bay (Qld)November 2024MG4
Red
50kWh
46. Harald MurphyPerthNovember 2024 Towing (inc Tasmania)Tesla Y White74kWh

* Supported by being supplementarily charged with liquid fueled generators which were either carried onboard or by a support vehicle.