Trip Planning

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Online Tools

There are a number of online tools available to calculate the energy requirements of a trip, although they all seem to have their own limitations, peculiarities and bugs.

Here is an example video of how to use Green Race: [[1]]

Manual Tools

Mark's Trip Calculator

When planning a trip over untraveled, hilly terrain I use the following calculations to determine if my Leaf has the required energy.

Key inputs are the cumulative elevation gain and the cumulative elevation loss. The cumulative elevation gain adds the change in elevation of all the rising gradients together, and similarly for cumulative elevation loss which adds the elevation change of all the falling gradients.

With this information, and a few other inputs allows one to calculate the energy requirements.

Constants include

  • Energy used when climbing a vertical kilometre (kWh/vertical kilometre)
  • Regeneration rate when descending (%)
  • Open road efficiency (km/kWh)

Download the attached spreadsheet [note to draft: haven't worked out yet how to attach a document to the wiki], and following the steps below, you can get an estimate for the energy requirements.

  1. Create and save a course on www.maymyride.com: http://www.mapmyride.com/routes/create/
  2. Take a note of the start elevation, end elevation, cumulative elevation gain ('Gain') and distance
  3. Enter the four variables above into the yellow cells in the spreadsheet
  4. Compare "Anticipated energy use" with "Battery capacity" (or "Equivalent flat distance" with "Maximum range on flat")

An example – Opotiki to Gisbourne

Take a trip from Opotiki to Gisbourne. Creating a course on mapmyride.com gives the following result:

MapMyRide.png

The start and end elevations are 7m and 9m respectively. The net elevation change is 2m. The cumulative energy gain is 1953m, and the cumulative energy loss is the cumulative energy gain less the net elevation change or 1951m. The energy requirements to lift of Leaf with a 450kg payload 1,000m is about 18 MJ (from m.g.h) which equals 5.0kWh/vertical kilometre. Multiplying this by the cumulative energy gain one determines that it takes 9.8kWh to make that ascent. Fortunately, some energy is regenerated during the descent, and using a factor of 35%, the energy regenerated is 1.951km * 5.0kWh/km * 35% = 3.4kWh. The difference between these two energies is the energy used for the elevation change over the course of the tirp, which in this case is 9.8kWh – 3.4kWh = 6.4kWh.

The distance of the journey is about 137.6 km. Dividing this by the open road efficiency yields the energy used on the equivalent journey on a flat terrain or 21.2 kWh.

In other words, the total energy anticipated to be expended is the sum of 21.2 kWh and 6.4 kWh which is 27.5 kWh. Or another way of looking at this, the equivalent “flat driving” trip would be 179km.

Below is the screen shot from the spreadsheet that does these calculations for you.

An example.png