Pele
Posts: 11
Joined: Mon Oct 05, 2020 3:47 pm

Usinig yesterday's drive to calculate today's range? Understanding the Guess-O-Meter?

I'm not entirely sure I understand the battery gauge on the dashboard.

I always start the morning's drive with a full charge off of my 240 VAC Level 2 EVSE.
I do NOT have Low Rolling Resistance tires on my FFE, so I probably have a range penalty due to this. I'm okay with that.

Thursday, I had to go to a remote facility at work which is ~50 miles away during a high traffic time. A lot of stop and go, but also a lot of highway driving. Started the day with an indicated 108 miles of range. Came home with a low battery warning and under 10 miles of range indicated on the dashboard. Plugged into my home's EVSE.

Friday, I went into the office. My office is ~25 miles away and there was also traffic at this time, so a lot of stop and go on the highway. I started the day with an indicated 94 miles of range. I came home with 40 miles of range and did not charge figuring I'd charge in the morning. I got called back into the office for a nighttime emergency. This time, I went into the office with little traffic, so 80 MPH highway travel. I arrived at my office with under 15 miles of indicated range and panicked because that will NOT get me home. I charged at the office using 120 VAC Level 1 EVSE for five to six hours I finished my work and headed home with an indicated 30 miles of range and got home with an indicated 1 mile of range. Plugged into my home's EVSE.

Saturday, I was hungry and decided to get some take out food for dinner. The location is 7.5 miles away with local road traffic. Some 25 MPH neighborhood driving, some 50 MPH road driving, many stop signs/lights. I started the drive with an indicated 90 miles of range. I returned home with an indicated 90 miles of range. (And like +20 butterflies on the right hand pane.)

I'm assuming the gauge uses yesterday's driving habits to gauge today's potential range.

Could I potentially have gotten home on Friday without charging at the office? (I know of a Chevy Volt owner that was reprimanded for charging at the office during the daytime when everyone could see, so I was reluctant to do that... However under the cover of darkness, nobody sees.)

How is it possible to have driven 15 miles on Saturday and not reduced the indicated range?

Why do I start the day off with varying range indications?
Anti_Climax
Posts: 398
Joined: Fri May 20, 2016 12:22 pm
Location: The Valley of the Sun

Re: Usinig yesterday's drive to calculate today's range? Understanding the Guess-O-Meter?

The specifics are fuzzy but the range shown at any time is calculated from a combination of your current trip efficiency and recent usage. If you made it home on Friday with 1 mile left on your range you definitely would not have made it without charging. The less charge in the battery, the less off the estimate can be in absolute terms. Though when the car hits 0% you do have an extra 1kWh of emergency reserve. Something to keep on mind - I actually had to use that yesterday myself.

Try to think of it in absolute numbers whenever you can. At any time, the car is estimating that you will have some particular average efficiency and it's simply telling you how far you can get with that efficiency and the remaining charge. Switching between surface streets and highway, uphill/downhill and even with and without climate power will change the values. Since the climate stuff averages over time the car will also estimate that usage and just subtract it from the amount it is using to calculate available range.

I make it a point to use the "MyView" setting on my left dash screen with Budget + Average with gauge scale on the right and accessory power on the left, no budget text.

Image

That range gauge has some very useful characteristics. At any time, the line across it shows your instantaneous Wh/mi and the ticks on the side show your average since the car was started for the current trip. If you aren't using nav to a destination, the highlighting on the gauge shows you the efficiency the car is using to estimate your remaining miles on your charge. If you are using nav it shows you the efficiency you need to average to make it to your destination with your remaining charge.

So if you consistently hold that line over or under the ticks, the ticks will move closer to it. If the ticks are inside that "range cup", not only are you meeting/beating the estimate, you can estimate how much better you're doing. Say your car shows you have 40 miles left and the range cup shows 300Wh/mi as the estimate, but you have the ticks sitting around 270Wh/mi and don't expect that to change. That means you're 10% more efficient than the car is guessing and you can expect to get about 10% more miles than it says. About 4 miles.

Depending on how it updates during your drive, that could mean that at 4 miles in it could say you have 36 left (no significant update to estimated efficiency), 40 miles left (efficiency estimate updated to "match" your actual recent efficiency) or somewhere between.

You can see on mine it's estimating 98 miles with an average of just under 300Wh/mile. Since it's been sitting, the efficiency for the trip so far is closer to 450, but that's not what I'm actually getting. But if I was, that means the estimated efficiency is 2/3 of my actual efficiency and I would expect to get ~66 miles on my remaining charge.

I really need to do a full illustrated post about this some day. I wonder how many people even know about that view, let alone the actual mechanics. If you have a feel for your typical efficiency on different routes, you can get a good feel for how much range you get from a given charge and start ignoring the meter.
2012 Candy Blue FFE
33.5kWh battery pack
CHAdeMO DC Fast Charging
Heima
Posts: 259
Joined: Thu Feb 21, 2019 11:46 pm

Re: Usinig yesterday's drive to calculate today's range? Understanding the Guess-O-Meter?

Yeah, the guessometer is pretty much that. But I use this thought process. The % of battery gauge is not linear, but fairly close. I know that 100% is 28 kwh (2017 FFE). I know that my typical consumption is approximately 250w/mile. If I am on the highway, it will be a little bit worse, if I am stop and go, it will be much better. So, 28000/250 is 112 miles. Which is about right. So if I see my % battery is 42%, then under average conditions, 42% of 28000 is 11760, 11760/250=47 miles. Lets say I need to go 30miles, 10 streets, and 20 highway. I will be able to do it because if I keep the highway speed under 60mph my worst consumption will be about 270w/mile. Lets say I need to go 50 miles, well, it will be close. If I keep the speed at 55mph, I should be able to make it.

Of course using climate control throws it all off. Not by a lot, but surprisingly enough to influence this reasoning.

Suggestion. Take some time to do some investigation. Plan a 5 mile route that has all the elements of your typical driving. Use the trip meter, reset it, take the 5 mile drive and see what your consumption is. Do it again with the climate control on. Do it again at a more hurried pace. This will tell you what your consumptions are, that you can make those calculations above for your vehicle and how you drive.

Then, the next time you need to go somewhere, consider what is the % battery, what is the distance, and will I use the climate control, or am I in a rush? And then you can make a quick calculation to let you know.
Pele
Posts: 11
Joined: Mon Oct 05, 2020 3:47 pm

Re: Usinig yesterday's drive to calculate today's range? Understanding the Guess-O-Meter?

Problem is that my driving is NEVER consistent as noted by my short week driving above.
I'm also still in the honeymoon phase of owning the FFE and still figuring it out.

I kinda like the spaceship noises it makes under hard acceleration and regenerative braking.
Right now, I'm sitting at a full charge, 75 Miles Range, and yellow bars in Acceleration and Cruising.
Anti_Climax
Posts: 398
Joined: Fri May 20, 2016 12:22 pm
Location: The Valley of the Sun

Re: Usinig yesterday's drive to calculate today's range? Understanding the Guess-O-Meter?

Can you start your car and post a picture of the Wh/mi gauge with scale from the MyView screen on the left?
2012 Candy Blue FFE
33.5kWh battery pack
CHAdeMO DC Fast Charging

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