"Full" battery levels dropping daily

[oilerlord]

I am not talking about longer term degradation of the battery. I am talking about the "full" level being 40-50 miles less on a rather sudden basis. The car is only 6 months old

Most modern cars (not only EVs) have range remaining displays. We commonly refer to the ones in our EVs as "guess-O-meters" because it's essentially what they do. They estimate / guess at range remaining based on your recent & real-time driving.

To SparkE's point, if you drive the same routes, the same speed, and at the same ambient temperature and wind conditions - the range remaining estimate can be quite accurate. They can also be notoriously inaccurate (and guess) at remaining range if your driving habits and environmental conditions fluctuate, or if other people drive your car. My range meter can fluctuate up to 50% based solely if my wife drives our EV, or if I do. It sounds crazy, but this is normal. There is nothing wrong with your car.

 

[boltage]

I am not talking about longer term degradation of the battery. I am talking about the "full" level being 40-50 miles less on a rather sudden basis. The car is only 6 months old

Most modern cars (not only EVs) have range remaining displays. We commonly refer to the ones in our EVs as "guess-O-meters" because it's essentially what they do. They estimate / guess at range remaining based on your recent & real-time driving.

To SparkE's point, if you drive the same routes, the same speed, and at the same ambient temperature and wind conditions - the range remaining estimate can be quite accurate. They can also be notoriously inaccurate (and guess) at remaining range if your driving habits and environmental conditions fluctuate, or if other people drive your car. My range meter can fluctuate up to 50% based solely if my wife drives our EV, or if I do. It sounds crazy, but this is normal. There is nothing wrong with your car.

The distance to empty displays in liquid fueled vehicles are not conceptually different, and are subject to the same fluctuations based on how efficiently the vehicle has been driven recently. However, some specific situations can affect electric vehicles and liquid fueled vehicles differently. For example, cold temperatures may lead the user to use the cabin heater, which is basically free in a liquid fueled vehicle, but expensive in an electric vehicle (seat heaters are much less expensive). On the other hand, driving down a hill in an electric vehicle can increase the mileage remaining, due to the potential energy at the top of the hill being regenerated into the battery.

 

[oilerlord]

Not conceptually different, just that the fluctuations are more severe with an EV than they are with a petrol based vehicle. If I drive my TDI at 50 MPH or 75 MPH, the difference in efficiency is about 7 miles per gallon. With it's 15 gallon tank, that's (roughly) the difference between getting 700 miles or 600 miles respectively, or a fluctuation of about 14%. Drive an EV at 75 MPH vs 50 MPH, and the fluctuation may be dramatic. Just a guess, but at a constant 50 MPH, I'd think the Bolt is capable of nearly 300 miles. At 75 MPH, I doubt it would be able to break 200. I think it's these fluctuations that gave rise to the term "guess-O-meter".

 

[gpsman]

I have done as close to a scientific measurement as possible.

I went an entire “tank” at 3.9 to 4.0 miles per kWh.
(3.96 miles per kWh is the EPA rating of 238 miles per full charge.)

Then I did a full charge.

When new, this = 238 miles.

Now, at 10 months and 10,400 miles, I get 234 miles.
A loss of 4 miles, which I attribute to age.

A loss of roughly 2% in roughly 10,000 miles.

If this keeps up (2% per 10,000 miles, 20% lost per 100,000 miles) that is pretty good.

At 100,000 miles on the odometer, it is resonable to expect .80 x 238 or 190 miles of range, when driving at an average of 3.9 miles per kWh.

 

[Anonymous]

I have done as close to a scientific measurement as possible.

I went an entire “tank” at 3.9 to 4.0 miles per kWh.
(3.96 miles per kWh is the EPA rating of 238 miles per full charge.)

Then I did a full charge.

When new, this = 238 miles.

Now, at 10 months and 10,400 miles, I get 234 miles.
A loss of 4 miles, which I attribute to age.

A loss of roughly 2% in roughly 10,000 miles.

If this keeps up (2% per 10,000 miles, 20% lost per 100,000 miles) that is pretty good.

At 100,000 miles on the odometer, it is resonable to expect .80 x 238 or 190 miles of range, when driving at an average of 3.9 miles per kWh.

The only way that would be scientifically useful is if you did that experiment a few thousand times and had all the same variables. Temperature, air density, wind speed, tire pressure, travel route, car weight, etc... would all have to be the same. That "loss" of 4 miles could just be within the error bars of your experiments.

Now lets say you did lose 2%, which could be very possible. Degradation of batteries is not a linear relationship. The Tesla people who have done this experiment showed the greatest lost of battery within the first 20,000 miles of being driven. After that, the battery degradation seems to slow down.

Only time will tell... It was also be variable amongst users. Some people may experience 30% loss after 3 years with minimal use. Some people may still have 90% battery after 300,000 miles driven. The Bolt has the newest generation of lithium ion batteries with an active cooling system. I didn't by a Leaf because of the high temps in my area and their passive cooling system. We need to compare the Bolt's battery degradation to the Volt and Tesla. The issues have been minimal with battery loss with those two examples, even with well over 100,000 miles driven in electric mode only. I use hilltop reserve because of the research that has been done with batteries, but we don't even know if GM gave us a buffer on the supposedly 60 kWh battery.

 

[boltage]

We need to compare the Bolt's battery degradation to the Volt and Tesla. The issues have been minimal with battery loss with those two examples, even with well over 100,000 miles driven in electric mode only.

The Volt may not be a good comparison, since it has a very large buffer capacity.

Teslas have different battery chemistry. But also earlier ones had the free Supercharging, which may have been harder on the batteries than nightly home charging.

 

[mwk]

So I've been wondering this myself. I'm a new Bolt owner. I've had the car for three weeks now. During my first week, when the car would tell me it was "fully charged", I'd see an "estimated range" on the dashboard of around 220 miles. Now, three weeks later, when the car is "fully charged", the dashboard is telling me I have "estimated range" of 185 miles.

I live in Boston, and it has gotten colder these last two weeks, over what it was the first week I had the car. Would cold temperatures (30's at night, 40's during the day), affect this range to that extent? Or, is there a problem I need to get serviced? Right now, I've only ever charged the car using the 120V charge cord provided, plugging into a weatherproof outdoor outlet at my house.

I did check to be sure Hill Top Reserve is turned off, and it seems to be. I did set up a home location charging profile so I could charge at 12 amps instead of 8.

Is this all normal?

 

[boltage]

I live in Boston, and it has gotten colder these last two weeks, over what it was the first week I had the car. Would cold temperatures (30's at night, 40's during the day), affect this range to that extent?

When the weather gets cold, do you use the cabin heater? That has a significant effect on consumption and therefore estimated range.

 

[mwk]

I live in Boston, and it has gotten colder these last two weeks, over what it was the first week I had the car. Would cold temperatures (30's at night, 40's during the day), affect this range to that extent?

When the weather gets cold, do you use the cabin heater? That has a significant effect on consumption and therefore estimated range.

I have used it, yes. But I've also tried turning it off entirely. It doesn't seem to make much difference.

 

[GetOffYourGas]

The Bolt uses a longer history than most EVs, in my experience. You may have to turn off the heater for a couple hundred miles to get that affect out of the range estimate.

Would cold temperatures (30's at night, 40's during the day), affect this range to that extent? Or, is there a problem I need to get serviced?

To directly address this question, yes the cold could have an affect to this extent. It is highly unlikely anything is wrong with your car that needs to be serviced.

 

[boltage]

I live in Boston, and it has gotten colder these last two weeks, over what it was the first week I had the car. Would cold temperatures (30's at night, 40's during the day), affect this range to that extent?

When the weather gets cold, do you use the cabin heater? That has a significant effect on consumption and therefore estimated range.

I have used it, yes. But I've also tried turning it off entirely. It doesn't seem to make much difference.

On a long flat bridge, I did some experiments with the cruise control set at 65mph with light traffic and minimal wind. Normally I see about 17-18 kW on the energy consumption display in the dash under these conditions. But I saw as much as 27 kW with the cabin heater on, indicating range would be significantly reduced if I kept it on (however, consumption would presumably go down some after the cabin gets to the pre-set temperature). Using the heated seats instead made no visible difference on the energy consumption display on the dash.

 

[SeanNelson]

Normally I see about 17-18 kW on the energy consumption display in the dash under these conditions. But I saw as much as 27 kW with the cabin heater on, indicating range would be significantly reduced...

My understanding is that the cabin heater draws a maximum of 6kW of power.

 

[GetOffYourGas]

Normally I see about 17-18 kW on the energy consumption display in the dash under these conditions. But I saw as much as 27 kW with the cabin heater on, indicating range would be significantly reduced...

My understanding is that the cabin heater draws a maximum of 6kW of power.

Here's a thread claiming the heater draws up to 9kW:
http://www.mychevybolt.com/forum/viewtopic.php?t=5752

Of course, that will even out once the car is up to temperature. The Leaf would give you real-time information about the power drawn by the heater. You would see it jump to about 6kW at first, and then steady out at 1-2kW (depending on OAT and heater settings). I miss having that information available. The Bolt doesn't give you a lot of that information, which would be handy when traveling in cold weather.

Edit: Just noticed that it was boltage who made that same claim. So who knows? There is some good discussion on the other thread though.

 

[gpsman]

So I tested this again. I drove even more conservatively. Last “tank” I averaged 4.1 mi/kWh.
It’s the miles per kWh that counts.
It does not matter how cold it is or how much cabin heat I used if I drove slower to compensate.

I just did a full charge up.
I got 229 miles on the range gauge (officially called “Confidence Gauge” by Chevy by the way... what we sometimes call “guess-o-meter”.)

I am at 10,800 miles. It really appears total range has dropped off a bit.

Once is a fluke.
Twice is a coincidence.
If it persists for a thrid time, this equals compelling evidence. If it turns out to be true, it’s actually reassuring that the computer adjusts with age and does not always assume a full charge = 60 kWh.

Not complaining. It’s within expectations. I’m just giving real world info here to those who are curious.

-John

P.S. what I have not done is drive from a full charge until the car quits. It is possible the car may actually go further than the confidence gauge predicts. But does anyone really want to drive to zero? I really don’t because this may have a permanent negative impact.

I have done as close to a scientific measurement as possible.

I went an entire “tank” at 3.9 to 4.0 miles per kWh.
(3.96 miles per kWh is the EPA rating of 238 miles per full charge.)

Then I did a full charge.

When new, this = 238 miles.

Now, at 10 months and 10,400 miles, I get 234 miles.
A loss of 4 miles, which I attribute to age.

A loss of roughly 2% in roughly 10,000 miles.

If this keeps up (2% per 10,000 miles, 20% lost per 100,000 miles) that is pretty good.

At 100,000 miles on the odometer, it is resonable to expect .80 x 238 or 190 miles of range, when driving at an average of 3.9 miles per kWh.

 

[WetEV]

It does matter how cold it is. Less energy can be stored in a 10C battery than a 30C battery.

http://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures

 

[gpsman]

I did this a third time.
This is East Bay California.
Daytime highs in the 70’s.
Lows in the 60’s.

Did a complete recharge at between 72 degrees (start) and 68 degrees (end).

Did really conservative driving for the third “tank” in a row. I have kept my miles per kWh at 4.0 for nearly 800 miles. This time I got 3.95 miles per kWh.
How did I get the extra digit?

I ran all tank at 4.0. Then ran heat while parked until it “just” rounded down to 3.9 on the dash display. Then I did a complete recharge. That is how I got the number that EPA used to calculate the 238 miles. (60 times 3.96 = 238 miles)

I’m now at 11,000 miles on the odometer.
Again, I got 229 miles per full charge at 4.0 miles per kWh.

This equals 58 kWh of predicted usable capacity.
However, I do not ever drive to 0 miles left. It is possible the car would exceed 229 miles at 4.0 mi/kWh. In my “tanks” I usually go from 100% down to about 25% with some partial recharges in the middle when I can opportunity charge before getting back up to 100%.

 

[SmokingRubber]

Had the car for 2 months now. My range is down to 169 miles on a full tank, with hilltop reserve off. That's a LONG way off the advertised 238!

I don't drive that fast, but my commute is 90% freeway (at 70-75 mph). I'm seeing consistently 2.8-3.0 mi/kwh.

Should I take it in and see if there's anything defective? 70 miles range less than advertised is pretty significant IMO.

 

[GetOffYourGas]

Had the car for 2 months now. My range is down to 169 miles on a full tank, with hilltop reserve off. That's a LONG way off the advertised 238!

I don't drive that fast, but my commute is 90% freeway (at 70-75 mph). I'm seeing consistently 2.8-3.0 mi/kwh.

Should I take it in and see if there's anything defective? 70 miles range less than advertised is pretty significant IMO.

At 2.8 mi/kWh, you should get 2.8mi/kWh*60kWh = 168 miles of range. There is nothing wrong with your battery.

Your efficiency is that low because you are driving 70-75MPH 90% of the time. That's pretty fast. Aero drag will catch up with you quickly.

My efficiency right now is about 1.8 mi/kWh but that's because it's 15F outside, I'm running the heat as much as I want, and driving through packed snow every day. My estimated range is 108 miles on a full charge. That's just fine with me for local driving - I rarely drive more than 25 miles in a day, and made it through 5 winters with a 24kWh Leaf. It does mean that I will not be taking the car on 700-mile road trips again until the weather warms up to at least freezing.

 

[gpsman]

I agree with Brian. Your car is fine.

However, here is what is interesting.
I made it a point to drive slower in winter, to counterbalance my brief heater use... usually just the first 5 minutes to dry my windows.

I made it a point to keep my average at 4.0 miles per kwh. AND MY GUESS-O-METER RANGE HAS GONE DOWN to 189 to 209 miles per fill up. At 4.0.

So it looks like the car’s mathematics AUTOMATICALLY deduct miles in cold weather, making broad assumptions. I have not run all the way to empty in a single day in months. But I will test this in 2 weeks. I’m going to drive 400 miles in 1 day in winter. (California winter. A.M. 35 degrees; afternoons 65 degrees.)

I suspect I will get very close to 238 if I keep it at 4.0.
(Which means driving at 60 mph most of the time.)

 

[WetEV]

I agree with Brian. Your car is fine.

Yes. Your car is fine.

AND MY GUESS-O-METER RANGE HAS GONE DOWN to 189 to 209 miles per fill up. At 4.0.

Do you have any way of measuring battery temperature? My guess is that your battery is cooler, and as a result can store less energy.

If so, the GOM may be giving you good information. After the trip, before the battery has cooled down, I suspect your GOM will be closer to 238 miles.