SparkE
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Tue Jan 08, 2019 7:10 am

BoltEV wrote:
SeanNelson wrote:
BoltEV wrote:...how do you suggest I take that measurement now?

I described the method in my first post in this thread.

Yes, I recall, but your method requires that I have a comparison measurement to when my car was new, which I never took.



Hint: skip the 'comparison' portion - you simply measure capacity, not capacity loss.

SeanNelson wrote:To get an idea of capacity loss, you'd have to look at the state of charge of the battery at the end of the drive, use the kWh to extrapolate the total battery capacity, and then compare that to the same metric from when the car was new.

For example, if you had a 5% charge left at the end of that trip, and assuming that you started with 100% charge, that means that the 55.5kWh you used for the trip represents about 95% of your battery (100% - 5%). That, in turn, would tell you that the battery has a capacity of approximately 58.4kWh (55.5 / 0.95). If you could compare THAT number to a similar measurement taken when the car was new THEN you'd have some indication of capacity loss.

In practice, the capacity figure you get by doing this bounces around somewhat, so you'd have to take the average of several readings to get a sense of what's happening with the battery.

BoltEV
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Tue Jan 08, 2019 6:06 pm

BoltEV wrote:Next time I will settle the debate by using the My Chevrolet app at the end of the drive to tell me the remaining capacity.

Yes, thank you.

I already acknowledged my mistake earlier and what I should have done to compute remaining capacity (other than driving until I run out of juice).

If the app reports X%, then, as Sean notes, the amount of full capacity would be the amount of Energy Used, divided by 100% minus X% (in decimal form).

I suppose it would be interesting to compute it both ways and compare!

SeanNelson
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Wed Jan 09, 2019 5:03 am

BoltEV wrote:
SeanNelson wrote:
BoltEV wrote:...how do you suggest I take that measurement now?

I described the method in my first post in this thread.

Yes, I recall, but your method requires that I have a comparison measurement to when my car was new, which I never took.

You asked how you could determine your battery capacity now. That's how to do it. There's no way to know what it was when the car was new if you didn't measure it then. The reason to measure the capacity now is so that you'll have a baseline against which to judge any future capacity loss.

cranial1963
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Wed Jan 09, 2019 9:46 pm

SparkE wrote:
BoltEV wrote:Thank you Sean.
So you are not convinced that we all have the same 60KWh capacity when new?

I have seen posted Torque Pro logs from other people, that they had taken when the Bolt was brand new, and a few were over 60 kWh, most were in the 57-59.x kWh range. It apparently does vary, by up to several percentage points.


I would agree, there are definite variances.
To me the simplest way to measure battery capacity/degradation is with an OBD II reader.
I use the LELink OBD-II Plugin with the OBD Fusion app and log measurements here and there.
You can see my capacity varied +/- about 1%-2% over the last 4-5 months:
01/03/2019: Battery Capacity: 59.26
11/25/2018: Battery Capacity: 59.22
11/14/2018: Battery Capacity: 58.83
11/03/2018: Battery Capacity: 58.52
10/29/2018: Battery Capacity: 58.93
10/18/2018: Battery Capacity: 57.92
10/16/2018: Battery Capacity: 57.96
10/06/2018: Battery Capacity: 58.69
10/03/2018: Battery Capacity: 58.87
09/26/2018: Battery Capacity: 58.49
09/16/2018: Battery Capacity: 58.66
08/29/2018: Battery Capacity: 59.78
08/26/2018: Battery Capacity: 59.85

In any case, having an OBD reader and app makes checking your battery's capacity a quick and easy thing to do.

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paulgipe
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Tue Jan 15, 2019 3:43 pm

I posted an article on our experience yesterday to my web site. See Tracking Chevy Bolt EV Battery Capacity.

Here's the gist on our Bolt after 14 months and 11,000 miles, mostly charged to 100%.

During the past five months our capacity has varied from 61.1 kWh, when I began recording the data from Torque Pro, to a low of 59.6 prior to a battery software update.

Image

For my use, capacity has hovered around 60 kWh--more or less--and that's what I need to know for the purpose of route-planning. So far, there's been no discernible battery degradation sufficient to reduce the advertised range of our Chevy Bolt.

Paul
Paul Gipe
2017 Bolt LT with DCFC, leased 11/09/17
2015 Nissan S with QC, leased, returned
2013 Chevy Volt Premium, used, sold
L2; ClipperCreek HCS-40; Jesla; JDapter Stub
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theothertom
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Wed Jan 16, 2019 12:05 am

paulgipe wrote:I posted an article on our experience yesterday to my web site. See Tracking Chevy Bolt EV Battery Capacity.

Here's the gist on our Bolt after 14 months and 11,000 miles, mostly charged to 100%.

During the past five months our capacity has varied from 61.1 kWh, when I began recording the data from Torque Pro, to a low of 59.6 prior to a battery software update.

Image

For my use, capacity has hovered around 60 kWh--more or less--and that's what I need to know for the purpose of route-planning. So far, there's been no discernible battery degradation sufficient to reduce the advertised range of our Chevy Bolt.

Paul

Looks like maybe there's 26 DCFC over the 14 month period? If so, I assume there were many L2 charges during that time. Mostly at 100%?

BoltEV
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Fri Jan 18, 2019 8:54 pm

I now realize that regeneration corrupts my abilty to accurately measure battery capacity through driving.

Is there any way to turn it off?

SeanNelson
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Sat Jan 19, 2019 2:57 am

BoltEV wrote:I now realize that regeneration corrupts my abilty to accurately measure battery capacity through driving.

Is there any way to turn it off?

Regen while driving doesn't affect capacity, it only affects range. Range and capacity are two different things. If you have an ICE vehicle with a 10-gallon gas tank, that 10 gallons on its own doesn't tell you anything about how far you're going to be able to drive, and adding 2 gallons to the tank partway through your drive doesn't change its capacity.

The "Energy information" screen in the Bolt tracks how much energy you've used, and it also tracks how much energy regen has put back into the battery. The result is the net energy usage. So if you've driven far enough that your battery level has dropped by 70% (for example, you charged to 88% in hilltop mode and drove until the battery only had 18% charge left) and in that time your net energy usage was 40kWh (which may include 45kWh of power and 5kWh of regen, (or not!)), then that indicates that your battery capacity is (very approximately) 40kWh/60% = about 57kWh.

BoltEV
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Re: How much will my battery degrade after two years of charging to 100% almost every night?

Sun Jan 20, 2019 6:39 pm

That answer begs the question, Sean:

I was discussing the possibility of driving until my battery ran out of juice and using the Energy Used gauge to tell me battery capacity.

However, regeneration will interfere with that measurement, so I was wondering if there is a way to turn regeneration completely off?

SeanNelson
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Location: Vancouver, BC

Re: How much will my battery degrade after two years of charging to 100% almost every night?

Mon Jan 21, 2019 9:33 am

BoltEV wrote:I was discussing the possibility of driving until my battery ran out of juice and using the Energy Used gauge to tell me battery capacity.

However, regeneration will interfere with that measurement, so I was wondering if there is a way to turn regeneration completely off?

Regen won't affect the overall measurement, unless the car has some sort of bias in that it erroneously measures 1kWh of regen put into the battery differently than 1kWh of energy used for propulsion. Nobody has ever suggested that this would be an issue.

The reason that regen won't affect the measurement is is because because the "energy used" reading includes the regen energy put back into the battery. Let's say that you drive up to a mountain pass and the Bolt tells you that you've used 10kWh of energy. Then you drive down the other side - as regen puts energy back into the battery the amount of "energy used" will go down - it might drop to, say, 5kWh used. Now you continue to drive along level ground using another 55kWh until the car runs out of juice . At the end of the run, the gauge would show 60kWh used: 10 - 5 + 55. Therefore, the battery capacity when you started was 60kWh. This assumes that you filled the battery, which resets the "energy used" reading to zero, before you started.

The only complication in this is if you recharge the car partway through the run by plugging it in. Unlike regen, charging does not subtract energy being put into the battery, all it does is reset the reading to zero if the charge completes.

Of course the car's measurement isn't 100% accurate, and the more regen you use the more the small inaccuracies might add up. But for a typical drive where the energy being regenerated back into the battery is a pretty small percentage of the battery's capacity I wouldn't expect it to be significant. Other factors such as temperature, driving style, individual cell variances, etc. are probably just as big a source of errors.

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