First MS road trip, comments and questions

[kirkbauer]

OK, after 2 months of ownership and close to 1500 miles I finally took my MS on a short road trip from Atlanta to Chatanooga. Here are a few thoughts, questions, etc. It was a last-minute trip so I had done very little planning or research. I had also already been out driving that day and hadn't recharged (I charge at night for the lower electricity cost).

So, first problem, I hop in the car and realize I'm at 58% which the trip planner said would get me there with 8% to spare. We start driving and within 5 minutes of our roughly 2-hour journey the estimated charge when we arrived to the supercharger in Chatanooga was down to 4%. I'm curious why this dropped so fast? Was it because the 5 minutes was mostly stop & go and stop lights and it started assuming we'd have worse than expected energy efficiency?

So my wife couldn't handle the stress and we diverted to the Atlanta supercharger which was about 15 miles out of our way, then charged to 80%. Would it have got better if we had kept going (e.g. returned closed to 8%)?

I was a bit worried that the high speeds which I'm used to driving will unnecessarily drain my battery and I'd have to drive slower to hit the estimated numbers. But surprisingly enough I drove 14mph over the speed limit virtually the entire way (in GA there are no points for that speed) and ended up only a few percent lower than it said I would have been (after the supercharger stop in Atlanta). This meant I was going 84mph for most of the trip.

I have my speed alarm/cruise control set to 14mph over the speed limit which is really nice. I really do wish that if you have cruise control set to the same number that this speed limit is set to, and then actual speed limit changes, that the car would adjust or warn you or something. I cruised by a cop and was hit by laser and only afterwards did I realize I was going either 19 or 24 over (can't remember now) because the speed limit was randomly lower there. I didn't get pulled over, fortunately, as I have defenses against that sort of thing

Finally I think the supercharger in Chatanooga is unusual since it is in an airport parking lot. It wasn't very convenient to get into our out of and there wasn't much to do there. I assume this is the exception and not the norm?

Overall I was very impressed with the entire journey but I wish I could have a few software tweaks that would have improved it:

1) Auto-adjust for changes in speed limit as mentioned above.
2) If I plot my route while supercharging then start driving, the gray line on the energy screen's trip tab shows the pre-supercharging plot. But once I start driving I'd prefer it to swap to the estimate when I unplugged the supercharger (does that make sense?). I just canceled the navigation and restarted it so no big deal.
3) I'd love to be able to do waypoints in the nav software

#3 is the big one for me. See, when I was at the Chatanooga supercharger, I needed to charge enough to make it to downtown for dinner and then all the way back home. But there was no way to do that. So I had to guess as to how much charge I really needed.

 

[Saghost]

Well, the good news is that in the autopilot demo at the announcement almost a year ago Tesla made a point of demonstrating the auto adjustment, so I'm confident it'll be a part of the final Autopilot package eventually - possibly as soon as the long delayed version 7 that is supposed to include Autosteering and should show up any day now (in Beta a month ago...)

The other two seem like reasonable and likely extensions to the Navigation, too - certainly Tesla knows that the routing through Superchargers is a little inconsistent right now.
Walter

 

[ecarfan]

You should routinely keep your state of charge (SOC) higher than 58%. Keep it at 80% at a minimum so the car is ready for a long drive at any time. The battery will be fine at that SOC.

 

[kirkbauer]

You should routinely keep your state of charge (SOC) higher than 58%. Keep it at 80% at a minimum so the car is ready for a long drive at any time. The battery will be fine at that SOC.

I probably wasn't clear, but I charge to 80% every night since I almost never use more than 20% of my battery each day. But in this case I had gone out with my kids that morning and the car doesn't start charging until 11PM during super-off-peak hours.

- - - Updated - - -

Well, the good news is that in the autopilot demo at the announcement almost a year ago Tesla made a point of demonstrating the auto adjustment, so I'm confident it'll be a part of the final Autopilot package eventually - possibly as soon as the long delayed version 7 that is supposed to include Autosteering and should show up any day now (in Beta a month ago...)

I meant to say that, yeah I'm assuming at some point AutoPilot will handle auto-adjusting your cruising speed based on speed limit.

 

[DFibRL8R]

Your state of charge estimate probably dropped because you were using energy at a faster rate than the car originally predicted you would. Perhaps a hot car with a hard pumping AC at the beginning of the trip or fast driving. As you go faster than around 40 mph or so the losses from wind resistance really start to increase. There are nice graphs on TMC that show you your potential range at various driving speeds. At 84 mph you are consuming a lot more energy than at lower speeds. As a general rule, if you are worried about making it to your destination, slow down. When you figure the extra time you took to detour to another supercharger you probably could have decreased your speed 8-10 mph and ended up at your destintion sooner. I also like to drive fast but have found as I have spent more time with the model S, I have learned how to get the most out of it and minimize my time stopping for charges.

 

[kirkbauer]

DFibRL8R,

That's what's strange. In my garage it said I'd have 8% at my destination. Five minutes later, with Range mode on and me driving conservatively, and having not gone above 60mph, it was predicting 4% at my destination. My guess is that it doesn't estimate surface streets too well (perhaps it assumes constant speed, not star/stop) nor slightly congested freeways, which is what I spent that 5 minutes doing. Perhaps it assumed I'd be doing that sub-optimally for my whole trip and reduced the final range? I definitely didn't burn all that much range in 5 minutes, it just changed its mind on the future usage.

When I decided to detour to the supercharger the same thing happened a bit. As soon as I left the supercharger and worked my way back onto the freeway, it dropped the destination estimate by a few percent. But both there and back, once I got onto the freeway at a steady speed, it held pretty steady. When I was going 84mph for a while I noticed the final charge estimate would decrease slowly, but at 79mph (in a 70mph zone) it held really steady.

I assume the estimate does include information on the speed of each road? Does it assume Range mode too?

 

[FlasherZ]

At the beginning of a leg, you'll get varied instructions from the car. On my trip to Florida, I left the Indianapolis supercharger, and after accelerating onto I-65, within 2 minutes I was instructed by the car to return to the Indy supercharger to top off again (??!). It recovered within 10 minutes of reasonable driving - but was reacting to the front end of the trip being a considerable divergence from what was expected.

As for Chattanooga, yes - that one is a bit of an exception. If the restaurant is open upstairs in the airport, it's a pretty reasonable place to sit and relax while you're charging.

 

[David_Cary]

First, you've explained Georgia drivers to me - thanks.

Second - By not slowing down and going to the extra supercharger, you gave a great example of what not to do. Of course it isn't just the extra 15 miles, it is the amount of time charging.

Someday there will be a good calculator on the car that says - you can drive 84 and go to an extra supercharger out of the way and arrive at 2:00 or you can go 75 and arrive at 1:30. Unfortunately right now the car wants you to arrive at 2:00 - to eliminate anxiety.

Unless they correct for it (which they obviously don't), nearly every trip will start out with decreased efficiency and the percent at arrival goes down. What is fantastic is the great yellow warning sign that your passenger can see. Once you've been on the road 20 minutes, the number should be more accurate.

The usual thing to do. You start out with 8% estimate at your destination. Drive a little slower than you might otherwise - like 70 in a 65 or 70 zone. Then when you get to 12% estimate, you creep up the speed. And when you are 30 miles away and have 60 remaining, you are up to 90 mph..... But seriously, roadtrips in an EV will usually start out slower and speed up as you get closer to your destination. Your buffer will depend on the distance to the destination. As you get closer, you need less of a buffer.

 

[danni]

I have my speed alarm/cruise control set to 14mph over the speed limit which is really nice. I really do wish that if you have cruise control set to the same number that this speed limit is set to, and then actual speed limit changes, that the car would adjust or warn you or something. I cruised by a cop and was hit by laser and only afterwards did I realize I was going either 19 or 24 over (can't remember now) because the speed limit was randomly lower there. I didn't get pulled over, fortunately, as I have defenses against that sort of thing

When the speed limit changes, you'll see a sign appear inside the speedometer. There's a configuration option to set the car to always display this sign when you're exceeding the speed limit, and an option for it to chime when you're exceeding the speed limit. To adjust the cruise control to the new speed limit, just pull the lever towards you and hold it there for a second.

 

[jerry33]

In my opinion, 8% is not enough leeway. Stuff happens, unexpected wind in particular.

It's often faster to not skip and charge less at each SC.

Whenever possible, start with at least a full daily charge because that or a range charge costs you no time, and shortens your next charge.

 

[HankLloydRight]

A few times I've been pretty low on estimated arrival charge %-- like 3 or 4%. When that happens, I get on the highway, set the cruise for 60mph, and just sit in the right lane for a while. Yes, it's PAINFULLY slow, but you do see the arrival % rise pretty quickly. When it gets to 8% or more, I start increasing speed a little, say 65mph. If I get to 10%, I just start driving normally, but still conservatively. When this has happened, the slow driving part is maybe 30 minutes. Sure beats detouring to another supercharger.

 

[TexasEV]

Even if it was a "last minute trip", didn't you have even a hour or so to charge at home before you left? Never mind that you charge at night when rates are lower, when you're going out of town you want to start with as much of a charge as possible. This car does take a little planning.

If you're borderline in range, the most important thing you can do is slow down.

Finally, if you may be taking these unexpected trips, charge to 90% routinely overnight rather than 80%.

 

[kirkbauer]

Even if it was a "last minute trip", didn't you have even a hour or so to charge at home before you left? Never mind that you charge at night when rates are lower, when you're going out of town you want to start with as much of a charge as possible. This car does take a little planning.

If you're borderline in range, the most important thing you can do is slow down.

Finally, if you may be taking these unexpected trips, charge to 90% routinely overnight rather than 80%.

Normally we don't do anything spontaneously, especially not like this, with two little kids.

Yeah, I should have thought to plug in while we were getting ready to go, but I didn't, still new to EV ownership