San Luis Obispo to Sunnyvale Hypermiling Thoughts?

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swogee

Well-known member
Joined
Jun 4, 2014
Messages
141
Location
San Luis Obispo, CA
I recently decided to take the RAV4 EV from San Luis Obispo to Sunnyvale (South SF Bay area) and back to see how long it would take to drive and charge. Our RAV4 EV has 7K miles on it now. The total distance is approximately 195 miles with most of it on US101. It's fairly flat with one 1300 ft climb out of SLO up Cuesta grade going Northbound and 500 ft climb going Southbound.

When I left SLO on Thursday (11/27) morning it the temperature in the high 40's to low 50's. I figured since traffic was lighter I could get away with going 50 mph so I set the cruise control to 50 mph except for when I was climbing Cuesta grade and I went 45 mph. My one charging stop was in Salinas at 129 miles at the Rabobank on N. Davis Rd. I arrived there with 4 bars left on the SOC meter. The average efficiency for the trip was 4.3 miles/kWh. It took about 5 hours to fully charge the battery. Theoretically, I could have left after getting 12 bars SOC since I had only 66 miles left to go to Sunnyvale but the Rabobank EVSE would be faster at charging than the dryer outlet at my mom's house. The last 66 miles I averaged between 60 to 65 mph and the avg efficiency was about 3.0 miles/kWh. The outside temp was about 72 degrees when I left Salinas. There were ten bars left on the SOC indicator when I arrived in Sunnyvale. I turned the climate control off during the trip. The whole trip northbound took about 8 hours, 35 minutes to go 195 miles. If I had cut the charge time in Salinas to about 3 hours it would have been 6 hours and 35 minutes.

On the trip back south on Saturday afternoon (11/29) to SLO I again averaged about 60-65 mph before stopping in Salinas to charge. The SOC meter had 10 bars left on it and the avg efficiency was about 3 miles/kWh. It took about 3 hours to fully charge the battery in Salinas at the Rabobank on N. Davis. At the start of the trip the temperature was about 65. On the last leg of the trip is when things got a little more interesting. I decided set my speed on the trip to SLO from Salinas at 55 mph. I was only averaging about 3.1 miles/kWh for some reason which I thought was lower than usual. This worked out to roughly 7 miles per/bar on the SOC meter. When I got to Atascadero I was down to the last 4 bars on the SOC meter. I noticed the SOC was dropping faster for some reason since it seemed as though the 3rd bar vanished after 6 miles and the 2nd bar disappeared after 5 miles. The terrain was mostly level with a few rolling hills. Once the SOC got down to 4 bars I reduced speed to 50 mph since I wanted to make sure I made it home. (Its hard to go much slower than that on a freeway and even at 55 mph the big rigs were all passing me.) Just before I got to Cuesta Grade, just south of Santa Margarita/Hwy 58, the SOC dropped to one bar. I was able to make it back home with only one bar left on the SOC meter. The temperature in Paso Robles/Atascadero was in the mid 40's and it climbed back up to the high 50's in SLO. The climate control was off the whole trip. The total return trip was 6 hours and 20 minutes.

So at this point it will take about 6.5 hours to get from SLO to Sunnyvale with one charge stop. I'm thinking it's not that practical since I need to make one stop to charge. This also assumes that the one 70A Tesla Roadster EVSE in Salinas is available (which it was for this trip). If there was a L3 charger in Salinas it would cut the trip down to about 4.5 hours which is better but the long distance between SLO and Salinas makes it tough. The only L3 charger north of SLO and south of the SF Bay area is in Monterey which is a 40 mile detour.

The other odd thing was that the RAV4 EV seemed to be getting less than the expected efficiency on the last leg of the return trip. I was thinking it would be closer to 3.7 at 55 mph. The rapid drop in the SOC on the last four bars also was peculiar since terrain was not much different than earlier in the last leg of the trip. I'm not sure why the last 4 bars had less range per bar.

Any thoughts or suggestions are welcome.
 
Was there a headwind on the return trip? That makes a huge difference

Over the holiday weekend I drove to College Station from Austin (116 miles). My house is at 1020 ft and CS is 338 ft above sea level. Weather was 65F. I drove 60-65 mph without climate control (as I didn't need any) and made it into town showing 3.3 miles/kWh and 10 miles left on the GOM giving a theoretical 126 mile range under those conditions. I charged on a Blink EVSE (208V/24A) for 9 hours for 44.9kWh (AC). Assuming 90% efficiency on the batteries and 85% efficiency on the charger, that's 34.3kWh (DC). Right at ~300Wh/mile or 3.3mile/kWh, just like the gauge said.

On the way back the weather was about the same, but had a 7 mph head wind. I made it into Austin's city limits at 105 miles with 5 miles left on the GOM, but still 11 miles from my house. My efficiency was 2.9 miles/kWh according to my dash. I stopped at a Charge Point public EVSE for an hour to get another 6.4kWh of energy back in. Luckily I had a football in my car so it gave my son and I something to do in the parking lot behind the Holiday Inn Express. It was actually good quality time, throwing the ball around with my son.
The last 11 miles to my house are mainly up hill, so it took everything out of the pack to get me there, even though I had 9 miles of extra range (had it been a flat road). Turtle mode came on as I was turning into my driveway. Plugged it into my AeroVironment EVSE (240V/30A) for 6 hours to fully recharge for 44.3kWh (AC). Adding the previous 6.4kWh and assuming battery and chargers losses, that's 38.8kWh (DC), or ~2.9 miles/kWh.

With these data points, I estimate the usable kWh capacity of my pack is ~35kWh after 40k miles on the odometer. Looking back at my charge logs when new, the most I was ever able to put in when driving down to turtle was 50kWh (AC) / 38.25kWh (DC). So by that metric, I've only lost 9% capacity. I don't use 41.8kWh (DC) because that may only be battery pack label (cell rating based on C/5 or 5 hour discharge) which is not how we drive our cars. I discharge my pack at slightly faster than C/2 rate, so I don't expect to get cell rated value.

I know there are a few of you out there with 40-50k miles on your RAV4EV. What are you experiencing? I'm still getting well over 100 mile range in the city and can reach 105-120 miles of range on the highway.

All that was said to show that a 7 mph headwind and a 682 ft rise in elevation over 100 miles lowered my driving efficiency by 12%. Luckily I didn't have to deal with temperature differences as well. I can't wait to get a JdeMo, even though there are only two CHAdeMo chargers in Austin.
 
Great data points.

I find that the fuel gauge "adjustment" multiplied by 2 is very close to the degradation. So, with a normal charge of 83-84% SOC when new, and now the same charge on #2496 takes 86%, I estimate the degradation at (86-83.5) * 2 = 5%

That car (#2496) has 16,000 miles and 10 months of service.
 
Kohler Controller said:
Was there a headwind on the return trip? That makes a huge difference...

All that was said to show that a 7 mph headwind and a 682 ft rise in elevation over 100 miles lowered my driving efficiency by 12%. Luckily I didn't have to deal with temperature differences as well.

The prevailing winds on the leg from Salinas to San Luis Obispo is a tailwind, but significantly uphill until the last 20-30 miles.

On your trip, to raise the car 682 feet requires (4398 pounds * 682 feet) = 3,000,000 foot pounds of energy

One kilowatt hour = 2,655,224 pound feet of energy, therefore (2,665,224 / 3,000,000) = 0.888kWh.

3.4 miles per kWh consumption rate is possible at 65mph (without heater, level, no wind, dry road, 70F), however your 7 knot headwind will decrease that consumption at 65mph to 3.0-ish.

116 miles range up a 682 foot elevation at 65mph STEADY SPEED (the speed doesn't vary, with cruise control ON) with the consumption adjusted to 3.0 for a headwind means that:

(116 / 3.0) = 38.7kWh, plus 0.882kWh for the elevation gain equals 39.6kWh. That's with zero heater use.

(116 / 39.6kWh) = 2.93 miles per kWh calculated consumption rate.

How did I do?
 
TonyWilliams said:
(116 / 3.0) = 38.7kWh, plus 882kWh for the elevation gain equals 39.6kWh. That's with zero heater use.

(116 / 39.6kWh) = 2.93 miles per kWh calculated consumption rate.

How did I do?

Except for writing 882kWh (instead of 882Wh), perfect!
 
The other big factor that causes efficiency to take wild swings is outside temp and weather (wind, rain, wipers, headlights). Combined with hills, a trip done in the Summer may be easily doable and trying that same trip in cold temps with weather may be a death blow for range. Remember that Tony's range guide is for 70 degrees.

I recently drove to Oregon for a few months from San Francisco and while there I encountered a huge rain storm ( monsson like) while out on a evening drive. The temp dropped to a little below 40 and going 45 mph, I could only manage to get 2.7 miles per kWh with the same hypermiling tricks that usuall get me 4 miles per kWh. My range remaining dropped so fast it was scarry. I hit turtle 2-3 miles before home. Turned off the wipers and headlights and drove with a flashlight out the window... A mile before home the car died. I turned it back on and it creeped along the last mile, by the grace of god, I made it. Hopefully I didn't hurt my battery :( I had planned to charge at a Wallgreens along the way, however, when I got there, the EVSE handle was missing ( got to love our all eggs in one basket, unreliable, infantile charging situation in the country, plus I drove right past a bank of Tesla Superchargers on the way, jealous, and a Chademo).
 
Thanks for all of the replies. So it looks like the main cause of the decreasing SOC in the last part of the trip was most likely due to the cool ambient temperature of 40 to 45 degrees? I didn't notice if the wind was blowing or not as it was dark on the way home. Typically the wind is from the NW in the evening so it is a tailwind as Tony mentioned.

So does anyone know at what temp the battery heater turns on?

I'm wondering if I should make another attempt at the trip up north on Dec 24th again or if the ambient temps will cause the range to diminish too much. I suspect the daytime highs will be in the low 60's and the lows will be in the mid to low 40's.

It's too bad there isn't a L3 charger in King City.
 
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