All posts by cs

Zone of Darkness

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They haven’t connected the dots between Louisiana and Alabama quite yet. In fact, there are no public charge station along this gulf route at all! However, RV Parks ( the kind that cater to 5th wheel trailers and self propelled Coaches ) have energy. The facility that I chose is clean, secure, was highly rated AND they furnished a 50 amp hookup. It is a standard MEMA 15-40 setup.

The rate of charge is about 28 miles for every hour so the car will be plugged in all night. I could have found my way to a hotel down the street but since I’m paying $38 for the assigned space, I will maximize this value and try ‘Car Camping’.

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mObridge for the Cayenne radio head unit

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The mObridge instruction manual that explains operation is a bit convoluted so follows is a step by step walk through.

Insert key into ignition switch.
This will supply power to the radio head unit.
Turn on the radio (if it wasn’t already on).
Wait for the radio to boot and then wait for
an additional 15 seconds as it will throw
the following error:

Press the button to clear the error.

If the radio head unit is not displaying
this screen then press the Audio
button (step 1) to display it.

Press the CD button (step 2).

The CD screen will be presented.

Note that you will want to be on CD 6
as shown above. The CD 12345 are
grayed.

If this is not the case then push the
button (shown below) to select
‘CD List’ … then rotate the button

until you arrive at the Menu/Aux Audio
line choice. Now press the button once
more to select that option.

The following screen will display next.

Press and hold the ‘ >> ‘ keypad button
to ‘ exit lock mode ‘. You will see
CD 12345 go to grayed.

Now you may plug in your iPod to the
iPod cable if desired.

Button 3 on the keypad is used to
select the Audio src (source)

There are three choices for source:
Aux (analog cable headphone jack)
A2DP (bluetooth digital playback)
iPod (digital iPod cable)

Select the source that you want by
pressing and holding the ‘ >> ‘ keypad
for 2 seconds until the source changes.
Then release. If you want a different
source then repeat the procedure.
Hint: If you didn’t hold the button in long enough
the source might not change as desired.
Instead the ‘ >> ‘ keypad button will scroll
out of ‘Audio src’. So, press keypad 3 to try again.

as Guest

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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!

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Public Charger Etiquette

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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.

End Point

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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.

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Cold Leg

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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.

Care and feeding

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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.IMG_7546

originality

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Dropping the fuel tank reveals a clean area protected from dirt and grime over time and from well meaning painters. The metal surface shows the factory finish — semi-gloss black. Knowing this, I will be able to scrape and sand and restore the undersides in original color.

clean area
clean area

EV Trip Planning

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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.

SPEED
45mph +26%
55 + 8%
60 100% of EPA rated range (at 70 degrees with miniscule HVAC)
65 – 8%
75 -26%
Headwinds can create significant energy penalty. Consider a headwind or tailwind component by using the speed table above. e.g. Your speedometer indicates 60 mph but you experience a 15 mph headwind — the transparent wind is 75 mph for a 26% reduction in range.
Optional: Hypermiling techniques, e.g. drafting a truck or inter-city bus +15% 
Optional: Large diameter ascetic wheel rims with very low profile tires -6%
Optional: Passenger windows lowered at cruising speed -4%
Note that all of the range penalties are cumulative.

The following table describes range corrections percentages to allow for road surface:
CONDITIONS
Clear and dry 100% of rated range
Wet roadway – 2%
Standing water -10%
Light snow -15%
Heavy snow -25%
This next table shows range penalties caused by temperature with respect to comfort and battery control. EVs must maintain an ideal temperature range for the economics of battery longevity.

HVAC referencing the outside air temperature (OAT)

15 -25%  at full blast, HVAC pulls about 7.5kW — battery heating is ncessary
32 -13% pre-heat the cabin if possible and then reduce cabin heat temp and use seat heaters. Optional cabin heat switched off (Brrrrrr) but still need battery heat -8%
50 – 7%
70 100% of rated range (HVAC on, but barely in use i.e. vent only)
100 – 7%
120 -13% there is energy draw for battery cooling in extreme

ELEVATION

Mountain -10 miles  in lost range for each 1000′ of Rise
Mountain +4 miles recovered range for each 1000′ of Descent
 
With experience a proficient driver can relax, put the sliderule down and properly estimate range by allowing a fudge factor. A general rule is to only count on 2/3rds of your advertised rated range. Planning a charge stop in this way, while conservative, will eliminate range anxiety. Also, there are calculators which will perform the math after you input certain values just as there are aircraft dispatchers who can do your flight planning. If you understand the principles explained here and dare I say enjoy working through the solutions then you might find aviation an easy transition. The mechanics are the same.