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Have a question I hope someone can help me with regarding the battery gauge/meter. For reference I have a 2015 Chevy Volt Premier.

When full the meter reads 45 miles of range.

I begin driving and the meter counts down mile by mile as expected until it hits 39 miles range. Then within the span of .25 miles it drops from 39 - 30 miles. Then, bizarrely, it will stay at 30 miles for about 6 miles of range before returning to dropping mile by mile as expected.

This behavior is consistent each and every time I have filled the battery and then drive it.

A) Has anyone seen a similar behavior?
B) Can anyone explain why this would be happening?

Thank you,
Oregon Volt Fan
 

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Your full charge range estimate is based on your driving history data the computer has collected. Once you start driving, the computer creates "on the fly" mileage estimates, multiplies the remaining fuel by that number, and comes up with a new range estimate.

One possible explanation if you’re talking about getting those results each time you drive a particular route: You drive the first 6 miles at the mileage rate the computer used to create the start of day estimate and the range estimate drops from 45 to 39. Then you start driving uphill, and because mileage drops as you drive uphill, after a quarter mile the range drops from 39 to 30 because you only have enough power left to drive 30 more uphill miles at that lower mileage rate. Then you reach the top of that uphill stretch, and start driving down a slight incline for the next 6 miles. You’re still using some power as your elevation decreases, but because you’re heading slightly downhill, the slow increase in mileage keeps the range at the same 30 mile range number for those 6 miles. Then you level off, mileage returns to the normal level terrain mileage, and the range estimate miles decrease again as expected...
 

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It is just an estimate (although we tend to think of it more as a "gas gauge"). When I start off into town the "gauge" will read 69 Km. The trip into town has some ups and downs but is at a higher level (as I'm going from basically sea level to inland) and by the time I get into town (8-9 Km) the "gauge" will read 70 or 71 Km range, probably because the battery has warmed up some and has increased its ability to produce energy. After that with some starting and stopping going to the different stores it will drop down to where it should be. I didn't get "free energy" from some of the down hill parts that over rode the uphill parts, it's a temperature thing. Although a different route/topography, yours could be a "temperature thing" too.
 

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I’m not sure your route, but I have the same “issue” every commute. However, it’s expected behavior. In my case, the reason for the drop is because I merge onto the freeway a couple miles into my commute and it drops quickly on the expectation that I will continue to use the same amount of energy. Of course, after I get up to speed and start cruising the rate of energy usage decreases and the estimate declines less slowly.

I believe GM made a determination to increase the estimate only under limited circumstances. In other words, it is more common for it to “slow” its rate of decline as opposed to adding estimated miles if conditions change. I’ve only seen it “add” estimated miles when engaging in heavy regen, such as a long downhill slope.
 

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If you are driving at a constant speed the whole time, and that happens, then it's not really normal. If you are merging onto a highway, or climbing a steep hill at the same time in your commute every day, then that sounds perfectly normal.
 

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Also, forgot to add—make sure there is no HVAC running or TMS. Bring up the climate screen and check the instant kW usage on the energy screen on the dash.
 

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Since this is the OP's first post, I think the collective assumption of "terrain demands", A/C use, etc. is probably accurate.

Please respond to let us know if this assumption is correct.
 

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The "fuel unit" used to evaluate electric car performance, 1 kWh, is just too small to be practical, because the distance one can drive on each unit is so very dependent on the terrain and environment.

We often forget that, and marvel over the numbers we see on the screen without considering how they were calculated...

My Chevy dealer is 6.1 miles from my home... I can drive there in my 2012 Volt using only 1 kWh of power!

My grocery store is 3.8 miles from my home, and most time I drive there, my ev range estimate increases by 1 mile by the time I reach the store! ...and then I look at the energy usage screen and observe I’ve actually used 0.6 kWh to get there, so how does the estimated range go up when the amount of power in the battery is going down?

I live at a higher elevation than those destinations... and I rarely pay attention to numbers from the same routes in the opposite direction (driving back from the store actually uses 1.8 kWh, so the ev mileage used to calculate an estimated range varies from 2.1 to 6.3 miles/kWh for that ~4 mile drive, depending on the driving direction!).

Analyzing "quirks" in range estimates as you drive can be a mind-numbing exercise.
 

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Discussion Starter #9
Thanks everybody for the input. I'll double-check this in the come week. But the drop in mileage from 39 down to 30 so far has been consistent whether going up hill or on flat land (I have two typical routes into town and one is hilly and the other is not). In all circumstances the A/C has been turned on (at level 1 fan speed).

I'll follow-up with some other routes and see if it does the same thing. The part I find the most odd is that when it drops to 30 how it stays there for about 5-7 miles. But if the computer is somehow doing an averaging function as you say, that could explain it. I just wish I knew what it was doing or how it was calculating.

Thanks again! Amazing how fast folks helped out. Much appreciated!
 

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So why is the INFO icon a CFL and not a LED :) in the above picture. I think for 2011-2012 volts it is a candle.

The car can recalculate SOC.

Lots of companies can make software to display battery charge state.

BUT no one had been able to reverse engineer the funky way GM handles the guess-o-meter :)
 

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Thanks everybody for the input. I'll double-check this in the come week. But the drop in mileage from 39 down to 30 so far has been consistent whether going up hill or on flat land (I have two typical routes into town and one is hilly and the other is not). In all circumstances the A/C has been turned on (at level 1 fan speed).
My 2012 exhibits similar behavior; same terrain, constant speed (typically 45 mph or less), no a/c, ambient temperature 65 to 85, etc. The only difference is that my guess-o-meter always starts at 35 or 36 miles of range. I have yet to get 40 miles of range this past summer regardless of how I drive.
 

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Discussion Starter #13
Since my last reply I have closely monitored the battery guage. The folks who indicated that the computer was providing an estimate and that the estimate would get more precise as I drove more and it learned my driving habits and routes were correct.

In the past week I have no seen this behavior at all and the battery guage's estimates have been quite accurate; even over the routes where I reported the behavior in the first post.

Thank you all for your input and help.

A Volt fan in Oregon
 
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