Trip Report - Bay Area to Sierra Drive

Br0dyman said:

Love seeing these posts. Thanks for the detailed write up. Do you know if temp number would mess with the efficiency yet? Like 71 degrees over 75 degrees. Or is it just the heater being on at all.

Click to expand...

That's a good question. I imagine that the "7% Exterior Temperature" is purely the energy used (ie realtime) to keep the battery (and other systems?) warm (via electric heaters) to what ever preset Ford determined that the battery modules should be. The warmer the battery, the better the discharge efficiency (to a certain point). So, yes, a 71 deg battery should be a bit less efficient than one at 75 deg. It's not linear, though.

Without an ICE creating all that heat there really is no way to warm the batteries without using their own energy, seems strange, but I'm used this effect. As a note, I'm an aerospace engineer and used to design spacecraft battery subsystems. Most batteries like to be warm as they discharge, so we would often heat up the batteries just before being used. In those cases, we had solar arrays to power the heaters. In our Lightning case, we only have either shore power (via the EVSE) or the battery as we roll along.

I'm not super aware of the heat pumps that others are using (like Tesla) that are used to strap excess heat from the electric motors (other than the obvious technology behind a heat pump). But, I can certainly see that being a great use of passive thermal technology, albeit at the expense of some mass (and cost).

Part 2 of my Road Trip
Round Trip: Cabin to Ski Resort

This morning I drove the Lightning to our local ski resort.
21.7 miles (no snow on the roads - it's still unseasonably warm here since last storms)
2800' elevation gain

Started at 80% charge, arrived at 67% charge ~ 17 kWhr
For some reason the display below didn't calc the efficiency (it was on the dash display, and I thought it was closer to 1.0). But, assuming the above data, this is about 1.3 mi/kWhr.
Note that had preconditioning on before I left. Nice warm cabin and battery. In fact, for the first few miles of my trip, the "Exterior Temperature" percentage was like 3% as was the "Climate Use." So, I would agree with the Ford folks, PRECONDITON your vehicle before leaving!
[Next trip to ski resort I will disable preconditioning to see how it effects these data]

On the way home, ahhh, the magic of gravity. I left at 67% charge and arrived home at 67%, yeah, basically no net battery usage. Note the pic on the right. 0% was used for driving! The energy regenerated replaced all the energy that was used for the motors. Of course, I'm a firm believer in the laws of thermodynamics, there was a loss, but I'm sure that the calcs the truck is making get messed up with such low usage vs. distance. The truck basically thought all my energy was being used to warm the cabin, the battery, and power my radio.

Per the computer, I got a whopping 12.4 mi/kWhr! Someday, all drives will be so efficient


Tagging @Ford Motor Company in case the engineers there find this interesting.

OK, follow-up on my trip to the Sierras. Here's the return trip data. I summarized both lengths in one table for comparison.

Summary:
1.7 mi/kWhr UP
2.2 mi/KWhr DOWN

As you can see the trips were pretty similar in terms of where the battery usage was. Almost same time of the evening and outside temps. We were driving down in the higher elevations in the snow (side note... these General tires are slippery....). Return trip was a bit shorter as we took a shortcut around the Livermore area (those from the area will know). As expected, Guess-O-Meter was not useful. However, the mileage calculator was almost spot on. It was great to see an average mileage of 6 mi/kWhr as we were driving down the steep front of the Sierras, but as we kept going, the computed mileage leveled out. As others have pointed out, it's the gage that you want to look at. Just have to do the mental math of percent remaining on your battery and the magical 131 kWhr full Extended Range capacity (98 kWhr for the Standard). Keeping with that, all (well, almost all) your range anxiety should melt away