Photo by the author.
The VW ID.4 and its siblings are known to be difficult to charge. In particular, the scheduled charging features don’t behave as owners expect them to. At this point, it is unclear if there are actual software problems or just user interface (UI) and user experience (UX) problems. These problems are sufficiently bad that the Internet is littered with whiny posts about the issue.
VW seems to have done a good job of anticipating how owners would want to charge their vehicles. They have not done such a good job of making it happen. This seems to be partially a UI/UX design problem in that the user interface is a bit muddled.
It also appears to be a result of clinging to the ICE fill up when the nag comes on model rather than adopting a different fill-up model suited to BEV home charging. We’ll explore this after the break and report once we have some experience.
- 2022-03-10: Original
VW’s Use Cases
VW has anticipated the following use cases in the design of the charging system. The charging menu directly supports these cases.
VW’s intent is that the vehicle would perform the prompt charge, that the vehicle would charge during the charge interval, and that the vehicle would charge outside the interval as needed to reach the target charge by departure.
Actors: Operator, Vehicle
Objective: Immediately charge the battery to a specified final state of charge.
The operator intends to charge the vehicle to prepare it for further use without regard to power demand management or price.
The operator intends to charge the vehicle in some specified time interval in the future. The charge may start on the current date and finish the following day.
The operator intends to take advantage of utility time of use incentives to perform the charge at a reduced cost.
Scheduled Charging following Prompt Charging
The operator intends to partially recharge the battery before going out for a short trip and complete the charge during the low rate interval.
Condition Vehicle for Departure
Complete charging prior to a set departure time. Establish cabin temperature and battery temperature to ready the vehicle for use at the departure time.
The vehicle completes the battery charge to the specified level required at departure. The vehicle heats or cools the cabin as needed. The vehicle establishes the battery temperature in the preferred operating range.
Most users begin by charging their battery electric vehicle like they were fueling their internal combustion vehicle. Operate the vehicle until the energy available is nearly expended then refill the energy store. This leads to weekly or twice weekly charging. But different strategies are possible. These realize that most of us have a work-driven battle rhythm and that the utility offers an aggregate demand driven energy price.
Fill up when the nag comes on
Drive the vehicle until the 62 miles (100 KM) nag comes on. Then charge up to 80 percent or so.
Charge for the next leg
Change the vehicle sufficiently that it can complete the next day’s operation or the next leg of a multi-leg voyage. The Out of Spec Motoring YouTube gang are keen on this model as it minimizes time at chargers on a voyage. It takes advantage of the non-linear charging behavior of the battery to half charge the battery several times in less time than a full charge requires. This requires some voyage planning to break up the trip into short segments between DC Fast Chargers.
Work Day or Week Day Charge
In this strategy, the operator does the following charging each weekday. In this model, the battery charge is maintained in a working range on the order of 20% to 50%.
- Prompt charge to provide enough power to take the kids to Little League, out for ice cream, or what ever the evening’s activity is.
- Over night charge at reduced tariff to ready the car for the following day’s commute or other anticipated travel.
This model is the charge for the leg model adapted to less structured local travel. Put in a sufficient amount of energy for the next day’s activities quickly.
Weekend Day Charge
This strategy recognizes that weekend electricity pricing is less than weekday pricing and that week end activity, although generally predictable, may include longer day trips to some attraction or opportunity venue.
A higher level of charge is established to support day trips in the local area. The vehicle is charged to 80% and may be discharged to a lower state of charge while returning from the outing, say 10 percent. VW vehicles appear to issue low energy advisories when 100 kilometers of range remain.
VW anticipated that the operator would prefer that the vehicle be ready for departure at some time with the vehicle doing the planning to complete the battery charge, cabin thermal conditioning, and battery thermal conditioning by the departure time.
One Location, Several Strategies?
I don’t think VW UI/UX engineers anticipated the activity based energy management model described above. ICE vehicles refuel at a constant rate. BE vehicles refuel at a rate that decreases with the amount of charged pumped into the battery. Frequent small additions of energy significantly reduce time on the charger compared to the fill it full model of energy management.
Why do our EV any differently? Because our electric power retailer offers different tariffs on days having different load profiles, one tariff for work days and one for non-work days. And our travel behavior is different on work days and non-work days. For example, we may go to beach or mountains on a non-work day needing more charge to complete the longer voyage.
And why do we tie the charge strategy to the location? I can have only one strategy for home plate and maybe another for the cottage and maybe a third if AC charging is available at work. And I can’t foresee more than 3 locations cataloged.
The new strategy is really tied to the upcoming activity. I use one strategy to ready the car for a workday commute, another to ready it for a day trip, and maybe that same strategy to ready it for the first day of a road trip that will include DC fast charging. Availability, demand management, and pricing considerations determine when the car should feed. Anticipated usage determines how much it should feed.
Meanwhile, the non-linear filling behavior of the battery is independent of 120V, 230V, or DC fast charging of the battery. The battery charges much more quickly from 5% to 50% than from 50% to 95%. This can be exploited both at home and on the road.
How VW organized the battery charging interface
VW have scrambled the vehicle mechanical information, such as it is, and the charging information together into a single group of displays. I, for one, would prefer to see the two charging groups and the energy usage group separated from the mechanical groups.
The current layout has divided the charging data into 3 views, the current charge view, the locations view, and the usage statistics view. These sections are grouped with the mechanical sections for the mirrors, braking, tires, locking, etc. VW manage to put the vehicle mechanical stuff in the middle of the vehicle electrical stuff. Kind of a dumb arrangement. And tracking down chargers is over in the navigation (reasonable as it is part of trip planning), and cabin preconditioning for departure is over in the cabin and windscreen clearing stuff.
- The current charge section shows the prompt charge, the scheduled charge, the current charging rate in miles of range added per hour charged, and the total charge in miles of range available.
- “Locations” having a planned departure time, a prompt charge target, and a scheduled charge interval with start and end times and a target charge. Cabin preconditioning could be enabled or disabled. Target cabin conditions are on another menu.
- Statistics for current day, since last charge, and vehicle lifetime.
- Locations pages are badly arranged as departure day-time is first, then charge parameters, and and finally charge time windows. On my first encounter I missed the fact that the display could be scrolled and that the time stuff was down below.
- Because the car does not know the charger’s capabilities, it cannot verify the time data entered. Not knowing charging rate, it can’t estimate duration. Without duration estimates, it can’t tell you the proposed charge plan is unworkable.
Vehicles delivered in 2021 and early 2022 have version 2 software running on the user interface. Apparently, Version 3 is being readied for the ID.Buzz launch and will be rolled out to the ID.3 and ID.4 when it is released for new production. Version 3 is expected to support the full IEC/ISO recommendations for customer authentication, vehicle and charger capability negotiation, utility and facility demand management, and settlement with the charging station operator and the energy provider. The automotive press lumps all of this under the rubric plug and charge.
Version 2 Software Expected Behavior
The Version 2 software appears to offer following charging capabilities.
- Prompt charging that begins when the EVSE is connected to the vehicle. Level 2 prompt charging is reliable unless something happens to confuse the vehicle and EVSE. If they get out of sync in the charging protocol, the car must be disconnected and the EVSE must be restarted. The charge can then be resumed.
- Location charging requires both a departure time to be selected and a preferred charging time window to be selected. If departure time or charging time period are not set for a location, only the prompt charge happens. And they’re not kidding, the car uses GPS location to select the rule set to apply. This is dumb as I’ll explain later.
- If initial battery charge is below the prompt charge target, the battery starts charging immediately. The charge should stop at the prompt charge target. If initial charge is above the prompt charge target but below the final charge target, the vehicle waits until time to commence charging.
- The car calculates time to commence charging. The car should wait until the estimated commence charging time. To calculate this time, it has to ask the EVSE the amount of current available. Then it can estimate the charging rate and charging duration. Knowing the departure time, it can subtract the estimated charging duration to determine the charging start time. So what do we subtract from, the departure time or the preferred tariff end time?
Note that the car currently knows nothing about the EVSE source strength, utility tariffs, or demand management needs until it communicates with the EVSE. A joint IEC/ISO standard covers charging customer authentication, utility and charging facility demand management communications, and settlement communications. This subject matter is all in the coming software update.
Issues seen in the field
The following things are happening in the field.
- The car is not verifying the combination of departure time and charging time window.
- The car is not telling the user the estimated time to complete the charge.
- The car is unable to advise the user that it is unable to complete the charge to the target level in the time available.
- The car is not asking the user to help it resolve inconsistencies in the charging plan. If the estimated charge duration is longer than the preferred charge interval, when should the extra charging happen? Before the start of the charge interval? Between charge interval and departure time? The car has no knowledge of time of day rates so can’t act in the user’s best interest. The car appears to sit there and sulk if any of these conflict conditions are encountered.
- The scheduled charge is happening at well less than EVSE capacity under conditions not yet identified.
Dismal Manor’s Wallbox
Dismal Manor’s Wallbox Pulsar Plus charger appears with the Millennium Falcon in the featured image. A 50 amp circuit feeds it from a 200 amp panel with 200 amp service. The National Electrical code allows a maximum single draw of 80% of cable rating or 40 amps.
Charging Rate Observed
At 40 amps, the Falcon charges at about 9.2 KW adding about 30 miles range per charging hour. A charge from 20 percent to 80 percent completes in under six hours.
Around Town Usage
In typical Dismal Dominion winter weather (0 C to 10 C) we are achieving about 3 miles of travel per KWH depleted. A typical day orbit of 30 miles is taking about 10 KWH so the Falcon can make 5 errand runs between charges to 80 percent. It takes less than an hour to replenish the battery following a typical day’s usage.
New Charging Plan
Since I can charge the Falcon at home, why charge just weekly? Why not charge each day from 20 percent to 30 percent right now and 30 percent to 60% during the 0000-0500 base load tariff? Most days, no prompt charge would be required. The charge to 60 percent would easily complete before 0500 unless the car became colicky for some reason and started charging below the rate supported by my EVSE.
Reports from the community is that such scheduled charging is unreliable using current UI software. I’ll give it a try next charge.