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Range cost for rain?

Discussion in 'Roadster' started by gregd, Apr 15, 2017.

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  1. gregd

    gregd Active Member

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    Quick question to the more experienced Roadster drivers... I understand that driving in rainy weather carries a cost in terms of range, due to pushing all that water out of the way. Not counting the effects of wind, what is the range cost for driving at 65 mph on wet roads, vs the same speed on dry? Tires on the front are the standard AD07's, and I have Pilot A/S on the rears.

    I'm committed to a trip this weekend, and it looks like my return trip will be in the rain. I generally don't take the Roadster out in the rain, so this is new for me. Nervous because the return trip is uphill, and I'm already stretching things a bit. So, yes, slow down. I know. I also don't want to get run over. So if I follow the flow of traffic, what is the impact?

    Thanks,

    Greg
     
  2. thefortunes

    thefortunes Member

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    Depends on the rain. Heavy where you may also need to run ac/defogger, or just a regular rain where the rolling resistance and aero is impacted?
     
  3. gregd

    gregd Active Member

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    Good point. It's warm enough that I hope I won't have to run the heat + A/C for defogging. That would cost me about 15%, if memory serves. I was just thinking rolling resistance and aero pushing the wet stuff out of the way.

    The trip is 160 miles, all freeway, and my range charge is just over 200. So, in theory I'm ok. But in practice, there is a difference between theory and practice...

    I'm planning to visit one of the Tesla Service Centers (Dublin, CA) on the way there today. The have two destination chargers (Tesla HPWC, 40 amps) available, along with their superchargers. Will see if they have the Roadster lock-out or not.... If not, that will be my backup plan for the return. If they do, there is another convenient set of public chargers further along the return path, that I might have to use, assuming they work too.
     
  4. ChadS

    ChadS Petroleum is for sissies

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    On a trip with really heavy cold rain (like, 35 degree F, so I was running heater and defroster) I once got about 2/3 of the rated range. That was the worst trip I ever did. But there was a fair bit of uphill involved in that too, so it wasn't just rain - it was rain+heat+elevation. At least it gives you a worst-case scenario. :)

    After analyzing Model S numbers, I once assigned 2-10% to rain, but of course that will vary by car, tires, how heavy the rain is (and how well the road drains it), etc.
     
  5. thefortunes

    thefortunes Member

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    I looked back at my records and for those days that I noted rain on my mainly highway commute (yes, I track my miles and kWh usage daily - don't judge :rolleyes:) I averaged 260-270 Wh/mi (about 10% higher than "normal").

    You should be ok, but I agree that it will be cutting it closer than I would prefer. It's good that you may have the option of charging at Dublin.

    If needed, you can offset the impact of rain by drafting a truck, but that is more difficult since it will typically be kicking up spray.
     
  6. KrenGrl

    KrenGrl Member

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    Interesting. I never thought about rain affecting mileage very much.
     
  7. gregd

    gregd Active Member

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    Thanks all for the info provided. Arrived with plenty of range remaining, thanks in part to being stuck in bumper to bumper traffic for about a third of the trip. The fun of traveling on a holiday weekend. It sounds like I should be ok on the return as long as things aren't too extreme.

    Good news about the Dublin Service Center. They actually have 4 HPWCs, and not only are they Roadster-friendly, I got 70 amps / 200 volts charge rate via Henry's CAN-SR adapter. I added 15 miles range during the short visit, so thinking a 30 minute stop on the return will do it. Two of the chargers are "owned" by Sales, two by Service. One of the sales guys promised to reserve me a slot for my return trip. They were having some sort of event there, very busy, but both the sales and service folks took the time to help me. Big kudos to Dublin, Calif SC.
     
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  8. hcsharp

    hcsharp Active Member

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    That's interesting. I wonder if they replaced any of those wall chargers at some point. I've had 3 reports that NONE of the Dublin HPWCs work with a Roadster. All three reports were over 2 years ago.
     
  9. gregd

    gregd Active Member

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    Must have been. Two of the chargers are immediately to the right of the SuperCharger stations, nearest the building. These are the ones referred to on PlugShare, I believe. They were both occupied with Model Ss, but I noticed that one had dealer plates so went inside and inquired about it. One of the sales reps moved it for me, and I charged. He said he'd leave one open for my return trip, since they'd be closed by the time I came through.

    The other two are under the car service lane drop-off roof on the other side of the building. All four were the same model. HPWC, 80 amp. They were NOT the model with the side holster for the charging cable

    On my return trip this evening, there was indeed one of the Sales slots open (the one next to the one I had used on the first stop), and I added a good 20 miles in about 30 minutes. But the taper kicked in, so I stopped it at about 204 miles Range mode when the charging had dropped below 40 amps, and moved on. Got home with 70-ish Range miles to spare (upper 40's standard), as I didn't have to use the heat or A/C, and I met up with a bit of traffic that slowed me down. The rain wasn't very heavy for the most part, but with the traffic and foggy/wet roads, most had slowed to about 55-60 mph through about half the trip. Crawled along for a short time. The rest was at 65. Overall, I almost broke even between Ideal and Actual miles (even with a 1,000 foot elevation gain at the end), which was unexpectedly good. During the few really wet sections, you could really feel the car slow as it pushed the water out of the way, so the effects of rain can be substantial. I just got lucky with the timing of the trip between squalls.

    By the way, I noticed during my first stop that the HPWC Charger + CAN-SR combination behaved the same as the Clipper Creek HCS-40 + CAN-JR. When I hit "stop" on the VDS, the charging stopped, then a moment later, started up again. One time I saw a charging error of some sort flash on the VDS momentarily, then it cleared. My guess is that if I had let the car charge to completion, it would keep restarting the charge briefly over and over again. I didn't play with it on the return. Just pushed stop, then got out and disconnected before it could change its mind.

    I'll pull the logs tomorrow and report if there was anything else worthy to report.
     
  10. gregd

    gregd Active Member

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    According to the log, the transient error while charging in Dublin was #1084, "External Charger Problem". That sounds about right. Didn't seem to be of any consequence (I did not have to do anything); just documenting it here for posterity. It did NOT re-occur while charging on the return trip.

    Trip home summary, from the logs:
    Starting SoC 95% (217 miles, I believe) Range mode
    Arrived in Dublin SoC 80%. Charged to 90% (added about 20 miles)
    Arrived home SoC 31%; used 244 Wh/mi on this leg
     
  11. dhrivnak

    dhrivnak Active Member

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    I frequently go to Knoxville in my Roadster taking the same lightly traveled roads at close to the same speed. I have seen my watts/mile vary from 198 to 290. The worst was a bad rain with substantial headwinds and needed to run heat and defroster. At 50 it was not cold but conditions were not fun. So yes rain has caused huge variations in power needed. Sorry there is not a simple or clear answer.
     
  12. gregd

    gregd Active Member

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    Thanks for the data. At 244 wh/mi. for my trip home, it appears that I was right about in the middle of your experience range. The trip out was 209 wh/mi. Besides the weather, there's a 10 mile 1,000 foot elevation change involved; downhill on the way out, uphill on the way back. I don't know what % basis that affects things, and since I live in the foothills and can't go anywhere without an elevation change, I may never know what "level freeway" consumption would be.

    BTW, the outside temp was 57F for most of the trip, according to the VDS display.
     

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