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TonyWilliams
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How to Check Battery Capacity, Degradation and Range

Sun Mar 25, 2012 11:03 am

RegGuheert wrote:I recently purchased a demo Leaf and just yesterday had a very similar excursion to the one which TickTock described in the OP. GOM was reporting 43 miles and five bars were left after driving only 32 easy miles starting from 80% charge.


Reg,

Congrats on your new car. I'm not sure how much you've followed along on here prior to your purchase, but nobody puts much thought into what the GoM says. Personally, I cover the thing, since bad data (to me) is worse than no data.

The only true method to determine how far your car will go is to actually drive the car from 100% to Turtle. The important parameters to consider are listed in the notes in the bottom of the range chart (link in my signature line).

If you ever think your battery is experiencing an abnormality, as previously suggested in the thread, try to duplicate a test drive in the same conditions (and preferably course) that you test drove when you bought the car. That means you have to make this run now, and then compare it to that same run in the future when you suspect an abnormality. You should always use climate control off, as there are too many variables there, and I suggest as level highway as can be found in your area.

Temperature is easy to match, but an important note is BATTERY temperature. If you just used a DC quick charger 6 times in a row, and the ambient air is 55F, your battery might be 120F.

Conversely, if your car is left sitting outside in the freezing cold overnight, but it's now 70F in the afternoon, your battery is not at 70F. This is a typical southern California winter weather pattern.

So, the baseline run when your car is new (and record all the data for future use) and a subsequent future run when you suspect a battery abnormality later needs similar battery temperature, ambient temperature (it's important to match up air density at the same elevation), same level terrain if possible (level terrain and steady speed will eliminate the variables of regeneration, because there won't be any), no heater or a/c (for hopefully obvious reasons), the same vehicle weight and dry road conditions. The end result should give you a baseline to compare your performances to consider battery degradation. Some great tools for data collection are Gidmeter or LEAFscan tools !!!

Some more notes to gather your baseline range data; you want a road where you can maintain a steady speed. To compensate for any wind and to compensate for elevation variations (you absolutely will be returning to the same elevation when you pull back in your driveway at the end of the test), I recommend 40-ish miles out, and return of 40-ish miles in the opposite direction, all at 60mph. If you can't travel at 60mph, match whatever speed you use with your estimated range; for example, 50mph steady speed can go about 97 miles per the range chart, so drive outbound about 45-47 miles before turning around for the return.

You need to reset your odometer and miles/kWh economy meter on the dash at the beginning of your run, but don't reset this data until you've collected the data at the end of the test. You should use the Nav economy meter (which reads 0.1 high with the present firmware) to get steady speed data. Get your car at the stable target speed (again, let's choose 60mph) and then reset the Nav economy meter while at that target speed to (hopefully) get the target miles/kWh at that speed. For instance, while on the outbound 40-ish mile leg, at 60mph with cruise control, hit reset on the Nav economy screen reset, and at the end of a continuous 40-ish miles while still at 60mph, expect to see 4.0 miles/kWh on that meter before you start slowing down to reverse course. Then subtract 0.1 to match the console date, to get 3.9 miles/kWh.

Then do the same on the return run. Get to speed, then reset Nav economy gauge, and read the result at the end BEFORE you change the speed. Again, if there's any wind, or elevation changes, or both, you'll get two different numbers for each direction. Again, do not reset the dash economy meter until you've recorded that data for the entire trip, from 100% charge to Turtle mode. Naturally, the dash miles/kWh number won't match your two way averaged 60mph Nav data (even when corrected -0.1), since you weren't driving 60mph the entire trip, like in your driveway, and through the neighborhood to the highway that your test was conducted on.

Its not so important to note fuel bars (but you can) as they are a variable In energy capacity per unit (but not as crazy as the GoM). For instance, the fuel bars will show 12 units at "100%" charge, even if the battery is -20C with 50% degradation. Important "hard data" landmarks are the mileage readings at Low Battery Warning, Very Low Battery, and subsequently Turtle. You don't need to drive the car to dead, just Turtle mode.

Check the tire pressure before a run! 36psi is recommended, many of us run right up to the 44psi limit specified by the tire manufacturer. Reset both economy meters and odometers. Do not attempt this on windy days. Do NOT use the GoM (that's just dumb) or CarWings (current firmware is off 2.5% for mileage). DO NOT USE AVERAGE SPEED.

BALANCE THE BATTERY CELLS FIRST!!! That means, charge to 100% and let the car sit for 4 hours after the car reaches 100% while still plugged in. Or, if you observe a top off charge between one and four hours after reaching 100%, you can then consider the cells balanced (as much as is possible). You don't have to do anything else. The LEAF's automation will take care of all the dirty work.

Checklist before the data collecting run:

1. Any changes to car from stock (different tires, bike rack, Texas cattle horns, etc)
2. Tire pressures set, heater and air conditioning off, car at 100% charge, cells allowed time to balance
3. Gross vehicle weight? 3350 pounds plus operator, passengers, spare tire, bags, concrete, etc
4. Route, length, elevation, hills if any, general conditions (dry, concrete/asphalt, etc)
5. Assumed or measured battery temp (from LEAFscan tool)
6. Ambient air temp
7. Gid count at start, if available
8. SOC, if available (from LEAFscan)
9. Starting total voltage (should be 393.5v from GidMeter or LEAFscan tools)

Data to record:

1. Outbound steady speed (confirm with cruise control on)
2. Outbound observed steady speed miles/kWh from Nav adjusted -0.1
3. Inbound steady speed (confirm with cruise control on)
4. Inbound observed steady speed miles/kWh from Nav adjusted -0.1
5. Miles at Low Battery Warning
6. Miles at Very Low Battery
7. Overall miles covered to Turtle
8. Overall miles/kWh from dash economy display
9. Calculated battery useable energy (miles / miles/kWh = battery kWh)
10.Ending pack voltage, SOC, and Gid (350v-ish from GidMeter or LEAFscan tools)

Post all this data on here for our crack team of LEAFers to decode, but plug the car in to recharge first!

Tony

jstack6
Posts: 137
Joined: Tue Dec 21, 2010 12:32 pm
Delivery Date: 28 Sep 2012
Location: Chandler Arizona

Re: How to Check Battery Capacity, Degradation and Range

Sat Jun 02, 2012 1:11 pm

In Arizona we have been gathering readings using a prototype SCAN GAUGE made by the local company linear logic right here in Tempe AZ. We have been finding all 1 year old LEAF vehicles that are charged to 100% read a battery capacity of 85-90% on the gauge. I'm trying to arrange to read some brand new LEAF's that are charged to 100% for a baseline.

We will also try to gather data in the Tesla, MiEV and FOCUS very soon. each EV maker seems to build the diag port differently which is where we gather data. We'll write up a report after we gather more data and have it on this site as well as in the Elec Auto Assoc. Magazine Current EVent.

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TonyWilliams
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Location: San Diego
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Re: How to Check Battery Capacity, Degradation and Range

Sat Jun 02, 2012 2:49 pm

jstack6 wrote:In Arizona we have been gathering readings using a prototype SCAN GAUGE made by the local company linear logic right here in Tempe AZ. We have been finding all 1 year old LEAF vehicles that are charged to 100% read a battery capacity of 85-90% on the gauge. I'm trying to arrange to read some brand new LEAF's that are charged to 100% for a baseline.


Yes, I believe "LEAFfan" has one of those in Phoenix. Is that the one you're using?

A new LEAF baseline will read 100% (or very,very close to that) if it has no battery degradation. There is no need to find cars to figure this out. What the SCAN GAUGE is reading is a value reported by the LEAF in digits 1 through 281. The instrument merely divides whatever value it reads by 281 to get a percentage. We have been using a similar instrument since last summer which we call the Gid-meter, and those values of 1 through 281, we call "Gids".

A single Gid is multiplied by 80 watt-hours to arrive at the battery energy stored to be used. 281 multiplied by 80 equals 22.5kWh stored energy. The battery, of course, can hold 24kWh maximum energy, but the top 5% and the bottom 2% are not available to protect the battery. Also, there are losses in using that 22.5kWh for your LEAF, which equals approximately 21kWh available to power the car. This all assumes a properly balanced battery at 70F or warmer.

So, if you're driving at 4 miles/kWh as reported by the dash, the LEAF can travel 4 * 21 = 84 miles. A cold battery will not hold 21kWh usable, and I use a rule of thumb of each 4F below 70F equals 1% loss in capacity. For instance, a 30F battery would hold 70 - 30 = 40F difference divided by 4 equals 10% loss, or 18.9kWh. Now, your same drive at 4 miles/kWh read from the dash will only go 75.6 miles. You would also have to drive slower to reach 4 miles/kWh since your heater will likely be on, using valuable energy that would otherwise be powering the car.

Another instrument soon to be released called LEAFSCAN will not only offer Gids, but much more data from the LEAF that neither the Gid-meter or SCAN GAUGE has access to. One of those data points is reported battery temperature, which will be quite important to folks with the LEAF in places like Phoenix.

Check out the range charts here to help understand the relationship of Gids to range. There is also a chart with 15% degradation (85% capacity) for your Phoenix LEAFs that have lost that first battery capacity bar.

Both can also be downloaded at www.LoveMyLEAF.com

Hope this helps,

Tony

Yogi62
Posts: 176
Joined: Sat Jan 12, 2013 7:29 pm
Delivery Date: 13 Apr 2013
Leaf Number: 405771
Location: Boston

Re: How to Check Battery Capacity, Degradation and Range

Sun May 12, 2013 10:01 am

Tony, I'm still trying to find a section of Massachusetts highway to do the range test as described. Level and constant speed are very rare. But I am 51.4 miles into a "100 mile on a charge" challenge and I am recording all of the dash and ELM327 readings for later analysis. Not shown are the air temps, in the mid 60's today, lower overnight. Given the additional data we have to work with now (2013 dash % and ELM327) and what I have recorded so far, what would your models predict for final capacity and range?

After adding some more usage, after adjusting for pack temp and indicated capacity loss in the app, the numbers appear to be converging on an original capacity of 21.5 usable KW/H.

Code: Select all

                Est.   Dash     Est.                                      Original
Dash   Dash     KW/H   SOC      Pack        Pack     @70       App        Pack
Miles  KW/M     Used   Used     KW/H        Temp     KW/H      Cap.       KW/H?
26.3    5.3     4.96   26%      19.09       66.3     19.26     93.79%     20.54
51.4    5.5     9.35   46%      20.32       66.9     20.47     93.86%     21.81
68.2    5.7    11.96   59%      20.28       69.4     20.31     94.04%     21.60
Last edited by Yogi62 on Sun May 12, 2013 6:02 pm, edited 1 time in total.

DougWantsALeaf
Posts: 287
Joined: Fri May 10, 2013 8:21 pm
Delivery Date: 18 May 2013
Leaf Number: 407811
Location: Chicago North Side

Re: How to Check Battery Capacity, Degradation and Range

Sun May 12, 2013 5:51 pm

Please post us on your findings. There have been some good single range tests posted around the boards, but repeatability is the key, as relative airspeed, road conditions, speed consistency etc.. all effect the end range.
2013 SV Black
Miles: 17500
Average Carwings/Dash Efficiency: 4.5-6.5M/KWh (summer) ~2.8-3.9 winter
100 Mile Club Member (Number 87), Max distance 120 miles

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TonyWilliams
Posts: 10032
Joined: Sat Feb 19, 2011 1:48 am
Location: San Diego
Contact: Website

Re: How to Check Battery Capacity, Degradation and Range

Sun May 12, 2013 6:49 pm

DougWantsALeaf wrote:Please post us on your findings. There have been some good single range tests posted around the boards, but repeatability is the key, as relative airspeed, road conditions, speed consistency etc.. all effect the end range.


All those things you quote (I like "airspeed") will be reflected in the "miles per kWh" economy.

So, we take miles driven divided by economy to determine battery capacity when driven from "landmarks".... 100%, 80%, LBW, VLB, Turtle, or using all the fantastic data we now have with Turbo3's new Android program.

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TonyWilliams
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Re: How to Check Battery Capacity, Degradation and Range

Sun May 12, 2013 7:30 pm

Yogi62 wrote:Tony, I'm still trying to find a section of Massachusetts highway to do the range test as described. Level and constant speed are very rare. But I am 51.4 miles into a "100 mile on a charge" challenge and I am recording all of the dash and ELM327 readings for later analysis. Not shown are the air temps, in the mid 60's today, lower overnight. Given the additional data we have to work with now (2013 dash % and ELM327) and what I have recorded so far, what would your models predict for final capacity and range?

After adding some more usage, after adjusting for pack temp and indicated capacity loss in the app, the numbers appear to be converging on an original capacity of 21.5 usable KW/H.

Code: Select all

                Est.   Dash     Est.                                      Original
Dash   Dash     KW/H   SOC      Pack        Pack     @70       App        Pack
Miles  KW/M     Used   Used     KW/H        Temp     KW/H      Cap.       KW/H?
26.3    5.3     4.96   26%      19.09       66.3     19.26     93.79%     20.54
51.4    5.5     9.35   46%      20.32       66.9     20.47     93.86%     21.81
68.2    5.7    11.96   59%      20.28       69.4     20.31     94.04%     21.60



Lots of great info, but I think you're assuming there is 100% to work with? It's really only about 95% CAP with a new battery with 2% not usable at the bottom (for 93% of 24kWh, or about 22.5kWh of "stored" energy). Of that 22.5, we have about 21kWh "usable".

So, lets look at some of your data. Your calculated 11.96kWh on the third line of data suggests 57% of 21kWh used; it looks to me like you're in great shape (is the 59% used estimated from the 2013 dash %?).

Good luck getting to 100 miles.

Yogi62
Posts: 176
Joined: Sat Jan 12, 2013 7:29 pm
Delivery Date: 13 Apr 2013
Leaf Number: 405771
Location: Boston

Re: How to Check Battery Capacity, Degradation and Range

Sun May 12, 2013 7:54 pm

TonyWilliams wrote:
Yogi62 wrote:Tony, I'm still trying to find a section of Massachusetts highway to do the range test as described. Level and constant speed are very rare. But I am 51.4 miles into a "100 mile on a charge" challenge and I am recording all of the dash and ELM327 readings for later analysis. Not shown are the air temps, in the mid 60's today, lower overnight. Given the additional data we have to work with now (2013 dash % and ELM327) and what I have recorded so far, what would your models predict for final capacity and range?

After adding some more usage, after adjusting for pack temp and indicated capacity loss in the app, the numbers appear to be converging on an original capacity of 21.5 usable KW/H.

Code: Select all

                Est.   Dash     Est.                                      Original
Dash   Dash     KW/H   SOC      Pack        Pack     @70       App        Pack
Miles  KW/M     Used   Used     KW/H        Temp     KW/H      Cap.       KW/H?
26.3    5.3     4.96   26%      19.09       66.3     19.26     93.79%     20.54
51.4    5.5     9.35   46%      20.32       66.9     20.47     93.86%     21.81
68.2    5.7    11.96   59%      20.28       69.4     20.31     94.04%     21.60



Lots of great info, but I think you're assuming there is 100% to work with? It's really only about 95% CAP with a new battery with 2% not usable at the bottom (for 93% of 24kWh, or about 22.5kWh of "stored" energy). Of that 22.5, we have about 21kWh "usable".

So, lets look at some of your data. Your calculated 11.96kWh on the third line of data suggests 57% of 21kWh used; it looks to me like you're in great shape (is the 59% used estimated from the 2013 dash %?).

Good luck getting to 100 miles.


Thanks for explanation of stored and usable. I was a little concerned that I might be down 5% after less than 1000 miles. Now it makes more sense. I was seeing 90.3% when it was colder out. Another degree of pack temp and it will be about 94.3%.

Yes, the 59% is based on the dash starting at 100% and now is 41%. I should hit LBW on the way home from work tomorrow, which is a 32 mile RT. I hope I am in a good place to stop and getting a set of readings when I hit LBW.

Yogi62
Posts: 176
Joined: Sat Jan 12, 2013 7:29 pm
Delivery Date: 13 Apr 2013
Leaf Number: 405771
Location: Boston

Re: How to Check Battery Capacity, Degradation and Range

Mon May 13, 2013 7:40 pm

Well, I went a little further than I planned. Right through LBW and VLBW but did not turtle, so the last dash SOC is a worst case estimate. It went from 6% to "---". App SOC started at 97.0%.

Code: Select all

                Est.   Dash     Est.                                     
Dash   Dash     KW/H   SOC      Pack        Pack     @70       App     
Miles  KW/M     Used   Used     KW/H        Temp     KW/H      SOC
26.3    5.3     4.96   26%      19.09       66.3     19.26     74.5%
51.4    5.5     9.35   46%      20.32       66.9     20.47     57.7%
68.2    5.7    11.96   59%      20.28       69.4     20.31     46.6%
84.7    5.8    14.60   74%      19.73       55.6     20.44     33.7%
98.5    5.7    17.28   82%      21.07       57.9     21.71     25.5%   LBW
100.1   5.7    17.56   83%      21.16       58.0     21.79     24.3%
117.1                  92%                  58.0               15.6%   VLBW
124.4   6.0    20.73   98%*     21.16       58.3     21.77     12.1%   Parked

DougWantsALeaf
Posts: 287
Joined: Fri May 10, 2013 8:21 pm
Delivery Date: 18 May 2013
Leaf Number: 407811
Location: Chicago North Side

Re: How to Check Battery Capacity, Degradation and Range

Mon May 13, 2013 8:41 pm

Wow, fantastic distance on a charge. What sort of speeds were you driving to keep the 6 Miles/Kwh? (I know what the chart says, but curious to see how real life situations map to it.)
2013 SV Black
Miles: 17500
Average Carwings/Dash Efficiency: 4.5-6.5M/KWh (summer) ~2.8-3.9 winter
100 Mile Club Member (Number 87), Max distance 120 miles

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