Planning to go from snow to surf in one day in an electric vehicle meant planning for resilience, to allow for things going wrong. Following a dawn-to-dusk schedule in 30-minute blocks also meant contingency planning, to know in advance what to do if things did go wrong.
Read more about the adventure, and read on here to learn how I extended already resilient EV trip planning in trippler to provide specific contingency plans, should charging preferences be unavailable.
Carnival of carving
We lay our scene on the descent from Mount Hotham to Cape Conran, snowboarding in the morning and surfing in the evening.
Complementing 2004’s Bitchin Barrels to Baw Baw Board Bonanza, we dubbed this adventure The Cross to The Cape Carnival of the Carve, and this time we were driving an EV.
Charge cascade
While the trip was “only” 250km (and effectively shorter considering 1800m descent), we weren’t starting full or finishing on empty. We were also racing the sunset all day. The plan, timed to 30-minute blocks, called for about 40% charge but, given we could easily spend two precious blocks waiting for an occupied charger, how should we decide where to charge on the day?
A trippler plan would guarantee we had backups for our preferred charging option(s), but the app at the time wouldn’t give specific contingencies. Instead, manually building this charge cascade gave us all the options up front.
It also showed when we would have run out of charging options to get to the surf before sunset. After all this preparation, however, plan A worked out!
Manual calculation and diagramming was fine for one adventure, but for future road trips I wanted a similar contingency capability in trippler.
Coding contingency
Thinking about the experience, and various approaches to contingency planning in trippler, I arrived at two new trippler features:
- Most contingency (optional) trip objective in addition to existing shortest time (default) objective, and
- Contingencies explorer to see the results of multiple iterations of re-planning the trip when charging preferences are not available.
Together, these give us contingencies for chargers on the planned route.
Configure the cascade
With further UI tweaks, we can configure the day’s planned driving in trippler:
This shows 250km of driving from Mount Hotham to Cape Conran, with three 50kW chargers en-route at Omeo, Bruthen and Orbost. We plan to depart with 70% and arrive with 50% SOC, with a range of 400km.
Most contingency
If we naively stuck with shortest time objective, as we see below, there’s a risk we’d skip past an available charger (eg Omeo) only to find the faster charge unavailable (eg Bruthen, deemed faster as marginally closer to the highway). Instead, most contingency objective picks chargers earlier on the route so we have, well, most contingency for unavailable chargers.
The new objective applies a penalty that increments with each successive charger. The planning solver then minimises this penalty, which also serves to minimise the number of charging stops.
However, we continue to ensure enough charging to reach our destination, as this optimal contingency result remains subject to all of the other resilience constraints trippler plans can be configured to satisfy, a neat result requiring minimal changes!
(If we do want to approximate the truly maximal contingency result of stopping at every single charger, we can increase the minimum SOC towards the highest satisfiable level.)
Contingency explorer
With extra contingency, I’d now like know exactly what action to take should circumstances require a change of plan. The trippler contingency explorer provides plans B, C, and more, just like the charge cascade.
Contingency explorer MVP version
The contingency explorer reuses the existing planning solver for each contingency but excludes relevant chargers per scenario. Also a pretty neat solution requiring minimal changes, and each contingency is in fact an entirely new plan!
Crushing constraints
The exclusion constraints require that unavailable chargers had previously been visited in the baseline plan order, but without any charging. I additionally scrapped previous no-backtracking constraints to provide more contingency options.
Backtracking on the Cross to the Cape route could be all the way from Orbost to Omeo after finding first (shortest time) preference Bruthen offline, and then first contingency Orbost offline too. This covers most of the route three times and doubles the trip time, but still satisfying other constraints!
Corralling complexity
The UX for backtracking is still evolving, as it is for the contingency explorer overall. While contingencies in general are a cascading or branching set of options for each charging stop (a dozen or more in total for a trip like Melbourne to Sydney), we don’t necessarily want to expose all this complexity, as on the left below. A simpler version may be to show some number of alternatives per charging stop, as on the right.
But after all this we can now explore the contingencies that provide the resilience for this trip and many others in trippler!
The carnival is over
For now at least, as may be the snow season, but I look forward to carving out more time for outdoor adventure soon.
As an aside, I learned an interesting thing about driving an EV in snow this season. If an ICE vehicle were snowed in and immobile, you would hear the engine rev as you pushed the accelerator to build torque to drive out. In an EV, however, if all your instruments are power-based, you get no feedback from the vehicle while pressing the accelerator deeper and deeper until the wheels start moving. This is because power is zero without motion (P = Tw), and it isn’t often the case that the wheels don’t start moving straight away! In this rare situation we’d need an electric potential or torque display for feedback. This may be a future OBD instrumentation project…
It was really satisfying to close out the carnival by coding the contingencies in the charge cascade in tripper. In addition to the improvements identified above, there are many more features waiting from here. Wherever it takes me, I am enjoying having my own resilient EV adventure trip planner but no firm roadmap!
