The road trip pauses to enjoy the hospitality of good friends at their lovely home in the Atlanta burbs. I borrow the wall outlet being used by the workshop wood lathe in the garage. This requires a special adapter for my EVSE (Electric Vehicle Supply Equipment) which adds a dongle to interface with this particular socket. Following a DYI allowed fabrication in advance of the visit.

This socket is 220v but 15 amp rated. I’m able to pull nearly 4kW from it. This not the most efficient setup; the onboard chargers like 10kW and can take up to 20kW. A 40 amp circuit would provide the 10kW which would allow for a faster overnight charge but I’m happy for the convenience on this location as the typical household outlet is only 115v. Thank you gracious host & hostess for the juice!

A smartphone app acknowledges with an IM when charging is complete. Even though it was late at night and unlikely that there would be additional patrons, I popped downstairs to the hotel garage to assess. I know that when I rolled in yesterday there was trepidation over availability. Not wanting to be that guy who thinks that the charge stall is his personal park spot, I was prepared to move and free the space. Luckily the opposite station was still open and I could remain. The EV was able to complete by 06:30 a cell balancing self maintenance.

Rappora developer Hint: An app that would alert the current (no pun intended) user when there is someone else in queue would be ideal.

Transiting a dark zone. The last stop was a fast DC charger in North Carolina but the only energy option from there until Atlanta are Level 2 chargers. These are scattered about many communities and work well for adding a few miles to an EV for travel that is local. A J1772 Level 2 charger outputs at 6 kW per hour. At that rate it will take 10+ hours to achieve a full state. This compares to only 75 minutes at the fast charger back in NC.

The South Carolina hotel I’ve chosen features 2 charge stations in their parking garage. I will explore their historic district on foot, have supper, and rest up for tomorrow’s journey continuation. The vehicle is plugged in and will be ready again by early morning.

Dipped into my safety reserve because of higher than normal energy usage. Pre-planning for 70 MPH, a 13% negative , cold weather consumed another 6% and that was with the cabin heat switched off.

I shall allow for this on the next leg by reducing speed at least during the early going. Once I see that distance to go balances with range available I can resume a regular rate.

Even with a garage temp of 45, the OAT Is 19 degrees and the traction battery is marginalized. The battery does not like cold. Observe the yellow dashed lines. These appear during these conditions so as to limit maximum current draw and maximum regeneration, either of which challenges the battery. Normal use creates heat. There is an electric element to provide auxiliary heat if required. When things get up to temp the limiters recede. In the pursuit of battery longevity we see how the system looks after itself.

Planning a trip in an Electric Vehicle (EV) is very similar to fuel planning for a cross-country in light aircraft. Before undertaking a journey you want to know enroute conditions, access performance data, locate fuel stops, have an alternate or a backup plan. EV range, like aircraft range is limited. Fuel stops are few and far between for either. The consequences of miscalculation for either can be serious. If you have aviation experience you will grasp the range planning concept readily.

The variables that can affect range, i.e. shorten or lengthen are:

• speed
• road surface
• temperature
• wind
• elevation change

There are other factors to consider exclusive to the EV such as cabin comfort; heating or cooling (HVAC) uses energy from the battery whereas a light aircraft uses waste energy from combustion exhaust manifolding to provide heat. A battery electric vehicle will suffer from some degree of vampire drain and parasitic energy losses -0.3 range miles for each clock hour vehicle moving or stationary.  Wheel and Tire design choices influence rolling resistance and aerodynamic drag. Passenger windows open vs closed can alter aerodynamics.

By far the biggest consideration is speed because of wind resistance. Drag is proportional to the square of speed,  and the power needed to overcome that drag is proportional to the cube of speed so if you want to go twice as fast, you’ll have to be eight times more powerful.  The following table shows percentage corrections to rated range and is based on driver reports and manufacturer guidelines.

The more cars at the gas pumps in a filling station the lower the pressure. i.e. unleaded may flow more slowly due to reduced pressure.  A Tesla Supercharger station is similar but first — how the Supercharger Station is engineered:

1. The utility transformers...
2. The 480 Volt disconnect switches and circuit breakers...
3. The charge controller cabinets. Each of these is as light beige in color, is about 24 inches wide, and has a large hooded cooling air duct in the back. Each Supercharger Cabinet contains 12, identical, modular chargers that are the same as the one or two chargers in an MS [model S]. The ones being installed currently can put out a total of 120 kW DC, shared between 2 charging stalls…
4. The pedestals (arches) at each charging stall.The pedestals at each charging stall are fed by the Supercharger cabinets and are where you find that nice, big cable and connector to plug into your MS. They are usually numbered 1A/1B, 2A/2B, etc. The numbers indicate the Supercharger Cabinet used, and the letters denote the pair of stalls serviced by each cabinet. The usual layout is 1A, 2A, … 1B, 2B, … This means that adjacent stalls are on different Supercharger Cabinets. If you want to make sure that you are getting maximum charging power, try to make sure that the paired stall (e.g. 1A paired with 1B) is not in use. If both charging stalls are in use, then priority is given to the first car to arrive, and the second car to arrive gets what’s left over.

The takeaway here is that the 120kW charge rate is a perfect case situation. If others are on the same Teat your rate of flow will vary [lower].

Tesla Model S has a mid year production update which means that if you took delivery before X date your unit has been superseded by something better. This can be expected with any leading edge technology but has the tendency to upset the early adopters. Remember ordering your first Pentium PC only to see the Pentium II intro mere months later rendering your box obsolete? Or smart phone, or tablet or…

First production vehicles are limited to a 90kW rate of charge. These cars have “A” batteries. Word gets out that updated “B” batteries, with the bragging rights of a 120kW hour charging rate have been incorporated into production. Somewhat unfairly, Tesla led folks to misunderstand that the higher charge rate would be enjoyed by everyone after a routine Firmware Upgrade which turned out not to be the case. Suddenly everyone is on their knees to look at the underbelly of their pride and joy to glimpse a factory VIN label proclaiming which batteries are installed with hopes that it will say “B”. Some are disappointed. Others find both letters mix and matched. Evidently there may have been a 4 month span when the new batter was ready but there were plenty of the “A” batteries still in inventory. Unfortunately those folks are also limited to the lower standard. Some people have newer car VINs with older style and some owners older VINs with the newer type leading to additional bewilderment.

This charge rate thing is meaningful. If you’ve spent luxury car money and your available time has considerable value, your wait at the charging station is measurable. The higher charge rate ability will get you back on the road perhaps 5-10 minutes before the Tesla owner with the lower limit. He might be left grumbling as you both pit stop and you are able to speed away first. This is a new world to understand. Those of us still consuming petrol don’t give a second thought to refueling. The Tesla owner when away from home base will strive to locate and use a Tesla SuperCharger location and by the way, Tesla’s deal is to provide a network of stations and make the energy available without cost to driver (as in FREE).

It becomes an interesting study in behavior as those first in line to buy the new car must have known that the original design, as wonderful as it is, was bound to be improved upon and enhanced over time.