Road trips are the most demanding EV scenario currently in Australia, especially to remote destinations. However, a little planning shows that they are still quite doable. Did the plans survive contact with reality?
Mostly.
In short, it was a pleasure to drive an EV long distances and the only inconvenience was faulty public charging infrastructure. This could have been a show stopper, however, had there been more faults, faults in different chargers, or the vehicle had less range.
Charger anxiety
I’m still confident heading off on road trips, but I’ve shifted thinking of charger faults from the exception to the norm, and shifted planning accordingly. Range anxiety isn’t a thing; but charger anxiety might be!
It’s something I’m willing to deal with to access destinations like this.
Plan vs actual
The plan was to stick closely to the “quickest arrival” charging profile proposed by ABRP. The outbound trip from Melbourne to the south coast of NSW is illustrated in the chart below, which shows the cumulative distance travelled over time, and the estimated range of the vehicle at each point. For reference, we include the minimum actual range estimate we had at any point (more on this below).
The trip starts at 08.30 and ends just after 16.00 (when distance flatlines). We make two ultra-fast charges (where the range line goes up), leaving us with nearly 2/3 full charge at the remote destination. However, the charge drops to a minimum of about 10% on arrival at the second charger.
With only an hour for two charging stops in this plan, we would probably stop longer the journey for comfort and recreation purposes, so there’s no compromise compared to an ICE vehicle in this plan.
The actual profile is illustrated in the chart below, with the same actual range estimate minimum line for comparison to the ideal plan.
It’s apparent that we charged more often than the ideal plan, maintaining a much higher minimum charge, and that we arrived nearly 3 hours later, at about 19.00. Of note, we spent an hour waiting for a functioning charger at our first stop (where range as well as distance flatlines). This is where reality started deviating from the plan!
State of chargers
What worked
Let’s first look at the functional chargers and then come back to the non-functional chargers.
At each stop, we charged at 50kW chargers, rather than 250kW+ chargers in the ideal plan. We were also charging at a higher SOC (typically 70-90%) than the ideal profile, meaning average power was less than 50kW. This is why actual charging took over 2 hours, rather than 1 hour in the ideal plan.
50kW average is fine by me at a vehicle efficiency of about 5km/kWh, as it represents a range replenishment rate of 250km/h, or 1 hour break for every 2.5-3 hours driving. If chargers have good amenity, such as food, parks, etc, and wait time behind other users is minimal, 50kW chargers make for leisurely road tripping, but they don’t make it infeasible. As above, we may have stopped for 2 hours total on the 7.5 hour journey anyway, even if we had infinite range.
One positive of more and longer stops was meeting other EV drivers. It was fun to connect and learn about their travels and their vehicles, and get accurate intel about chargers up and down the route.
Faster charging is of course better where available. Reduced charging cycle time minimises travel time, increases vehicle throughput per charger and, in terms of resilience, it also reduces the chance of extreme wait times behind other users.
What didn’t work
The bigger issue was non-functional chargers. Our vehicle completely failed to charge at one of the major charging networks – the one we’d planned to use at both stops – despite a successful test before the trip. It’s hard to say if the fault lies in the network, the vehicle, or the robustness of standards, but the end result was unusable chargers in any case.
There was another site on a different network just 3km down the road from our first stop, but two of the four chargers were non-functional (the faster chargers, of course), which caused the hour wait behind other drivers prior to our first charge.
This fault wasn’t properly reflected in the various charging apps, and further stations that were reported offline were actually working, so we decided not to rely on the reported status of chargers!
Compensating
Although from that point on, the alternative network’s chargers worked well and we had no further issues charging, we remained concerned, and charged as much and as soon as possible so that we were as resilient as we could be. As you can see from the actual chart, we had a lot of range to spare, but if we’d run the range down to 10% on arrival at a remote unusable charger, we may not have been able to reach another charger. If we’d approached 30%, we wouldn’t have had the option to skip any long queues.
Note that on the return trip we only needed to charge twice. We picked functional chargers from the outbound trip. We also had progressively more charging options the more dense the population as we returned home, and could sacrifice resilience (reserve range) for efficiency (shorter charges). We arrived home with 16% SOC.
Vehicle efficiency
Where reality beat the planning was in the vehicle efficiency. Estimating about 4.3km/kWh as the base case, we were able to get closer to 6km/kWh in city driving, about 4.5-5.0km/kWh on highway and gently undulating country roads and about 4.4km/kWh on windy and hilly country roads.
Reducing speed from 100km/h to 95km/h also seemed to have a positive benefit of up to 0.5km/kWh but we didn’t test this under controlled conditions.
This was at the base case described in EV adventuring, as we weren’t dealing in a major way with range-reducing external gear, net elevation gain, or problematic weather or road conditions.
Resilient planning
What I’ve taken from this experience is that an ideal charging plan for an EV road trip may need multiple back-up options, as of now, in Australia.
Our rule of thumb was to always maintain enough charge to go on to the next charger after our target, or return to the charger we’d just left, in case the targeted charger was non-functional (regardless of what status may be reported in any given app). This requirement becomes more demanding the more sparse the charging network, such as in rural and remote areas.
It becomes more demanding again in the case of an out-and-back trip to a remote destination, which is why we aimed to reach our campsite with 67% SOC, in case the final charger was non-functional on the return trip (which would have required us to travel 330km between charges). I think this is also good practice in remote areas where there might be a risk of natural disasters, as the Australian summer of 2019/2020 demonstrated.
ABRP provides a number of options to improve resilience of a charging plan, such as exploring alternative chargers, and specifying a minimum SOC before charging is triggered, which I’ll explore more fully on my next road trip. If these don’t meet my needs, I’ll think further about how to fill the gaps. The most resilient plan may look a lot different to the ideal charging plan. It’s also possible the charging network could be intentionally designed and managed to improve the resilience of more road trips.
For now, it’s back to less demanding EV scenarios for a while (and more cycling as an alternative to driving too!), and dreaming of the next road trip.