Better (reverse) SOC meter already in the car?

surfingslovak said:

TonyWilliams said:

evnow said:

Actually the "gids" are not linear - at least near the top (and most probably near the bottom). I had a thread about it sometime back. That probably reflects the difficulty in getting a good measure of SOC near the top & bottom.

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Agreed, it's not linear. My statement is the Gid data is perfect (for me) for an SOC meter. Just a teeny, tiny amount of math is needed on the top and the bottom to make it linear.

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+1

I continue to gather data, and I'm quite impressed with the accuracy this method provides when trying to predict the remaining available energy, especially at a low state of charge. It's very good, but you are correct, the reverse SOC can in the best case be only be as accurate as a gid-o-meter would be.

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I think I need a tutorial for dummies on how to best use this method. Can you make one ?

tks

mdh said:

I think I need a tutorial for dummies on how to best use this method. Can you make one?

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Matt, happy belated New Year! This took a lot more effort than I anticipated, but here are my preliminary results.

The abbreviated version of my spreadsheet I linked to below is based on a dozen of battery cycles and about 500 individual odometer and energy economy readings. The majority of the cycles were 80% charges, but I went to 100% several times as well. Although I had to push the limits on occasion, I solemnly swear that no Leafs were harmed during the testing!

I'm happy to report that this approach is both practical and reasonably accurate, although it does take some work. But then, what doesn't? The data I've gathered indicates that one hour on the 120V charging display corresponds to 840 Wh on average. This value can go up and down, and I have seen lower figures especially when charging to 80%.

Turtle mode kicks in at 25 hours on a 100% charge and at 21 hours on a 80% charge. The very low battery warning comes one hour earlier, and there appears to be about 1 kWh of usable energy in the battery at that point. Low battery warning is generated at 21 and 17 hours respectively.

These readouts are quite consistent, and they can be used to determine the SOC nearly as well as Gary's meter, albeit with less granularity. As lukati and 91040 determined earlier in the thread, each hour corresponds to about 11.6 gids.

Please keep in mind that the mapping to battery bars is not quite finished, and it was only included as a point of reference. The tutorial is coming, I promise.

George

surfingslovak said:

This took a lot more effort than I anticipated, but here are my preliminary results.

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Definitely worth the wait! Looking great.

surfingslovak said:

This took a lot more effort than I anticipated, but here are my preliminary results.

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Thanks for the work and the chart! I'm checking the chart against what's reported by Carwings and matches up for me (currently reports 8 bars, 7.5 hours 120V, 2.5 hours 240V). Was confused for a bit because Carwings reports time to 100% even though my timer is set to 80% 7 days a week.

lukati said:

Definitely worth the wait! Looking great.

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Thank you, much appreciated! I found the data analysis you did earlier in the thread very useful.

drees said:

Thanks for the work and the chart! I'm checking the chart against what's reported by Carwings and matches up for me (currently reports 8 bars, 7.5 hours 120V, 2.5 hours 240V). Was confused for a bit because Carwings reports time to 100% even though my timer is set to 80% 7 days a week.

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Yes, that's good to hear and thank you for your patience. Carwings has a number of quirks, and this is definitely one of them. It does not respect the 80% charge timer, and it always shows the time needed for a 100% charge.

I would like to refine both the model and its presentation. It will be crucial to have access to more data, and if you were able and willing to help out, that woud be much appreciated. I plan to make the spreadsheet available both on the web and in the form a mobile app. Beta testers would be greatly appreciated.

A new version of the chart is available on Google Docs. I cleaned up and reformatted the spreadsheet, and both the estimated usable battery capacity and energy economy can be easily accessed and edited. This should help tailor range estimates to your car and driving conditions. I did not have time to refine the underlying model, although I would like to do that in the not too distant future.

If you would like to edit the spreadsheet online, you can do that for the time being. It's important to demo the potential of this approach, but I might have to restrict access if things get out of hand. Obviously, you can always download a copy and use as you seem fit. Thank you to everyone who has sent a PM, your feedback and correction requests are greatly appreciated.

The discussion initiated by Phil in another thread and the data presented there prompted me to update the spreadsheet. Version three is now available on Google Docs.

The revelation that Gids represented stored energy and corresponded to 80 Wh, allowed me to come up with an fairly simple model, which I used to replace the empirical data I've collected over the course of two months almost seamlessly. I feel much more confident about the data presented in the spreadsheet now, although the mapping to battery bars is still a bit iffy. I pulled up Tony's range chart as a reference, and tried to fix it, but ran out of time and had to admit defeat on that front.

The SOC column has been renamed to indicate that it's only an estimate, since we cannot reliably derive a true SOC reading from Gids or the hours on the charging time display. This estimate equates 300 Gids to 100% SOC, and it assumes that there is no additional reserve beyond the 4 Gids remaining in the battery when the car stops dead after turtle.

I've created a new column that indexes the energy available to the driver from 100% to 0. Perhaps this will be more useful than what we had previously. And finally, I've included a column with Gids. This is based purely on the assumption that each hour on the charing time display is 11 Gids. Surprisingly, this simple model, combined with the observation that there are 25 hours max on the display, delivers unexpectedly good results. It predicts 232 Gids for an 80% charge, where I typically observed 231. It also predicts the Gid value for LBW and VLBW quite accurately.

I moved the 25-hour mark down a notch to indicate that the car can enter power-restricted mode (announced by disappearing power bubbles) a bit earlier. This was driven by the model, which predicts very low energy at the 25th-hour mark. I observed this twice, most recently in January. On another occasion, I was able to drive a mile or two beyond this mark without any trouble. In any case, the car won't go very far once you see 24 hours on the charging time display.

Your feedback and correction requests are greatly appreciated.


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Thanks for posting these range estimation charts. I used them yesterday and they worked great. I noticed that there is another post that mentions a voluntary recall to update the calculation on the "time to charge" display.

http://www.mynissanleaf.com/viewtopic.php?f=27&t=7861" onclick="window.open(this.href);return false;

Anybody know more about this or have this service performed on their leaf? Did it make a difference in the carts predicted range?

shtimseht said:

Thanks for posting these range estimation charts. I used them yesterday and they worked great. I noticed that there is another post that mentions a voluntary recall to update the calculation on the "time to charge" display.

Anybody know more about this or have this service performed on their leaf? Did it make a difference in the carts predicted range?

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Thank you for your feedback. Glad to hear that you found this information useful. If you saw any inaccuracies or room for improvement, please let me know.

I've been ignoring your research on this, but finally decided it was time I paid attention. I have two questions:

• Are the Gids shown the max, mid, or min for the time? e.g. if Gids=218, would you expect to see 1:30 or 2:00 for a 80% charge?
• Your chart clearly shows an "80%" charge as 80% of usable. Phil (Ingineer) has told us that it is really 80% of SoC. (See this post.) That would put it at about 85% of usable. Has your testing shown convincingly that he is wrong for once?

Ray

planet4ever said:

I've been ignoring your research on this, but finally decided it was time I paid attention. I have two questions:

• Are the Gids shown the max, mid, or min for the time? e.g. if Gids=218, would you expect to see 1:30 or 2:00 for a 80% charge?
• Your chart clearly shows an "80%" charge as 80% of usable. Phil (Ingineer) has told us that it is really 80% of SoC. (See this post.) That would put it at about 85% of usable. Has your testing shown convincingly that he is wrong for once?

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Ray, thanks for considering this approach. Although I have gathered well over 1,000 data points, I should note that the spreadsheet represents a fairly simple model as of this writing. Each hour on the 120V charging time display represents 11 Gids, and your Leaf will be dead once you have passed the 25 hour mark. Empirical data seems to fit this model reasonably well, but there was too much noise to claim more than 3-5% accuracy. The linear relationship between Gids and hours to charge was established with the help of Gary's meter. The SOC % is just an estimate derived from the Gid count, and so is the total usable energy percentage.

You mention 80% charge. The model predicts 82% usable and 77% SOC, which is about 3% from Phil's numbers, and would be consistent with the accuracy implied in the model. For what it's worth, the empirical data I've gathered always indicated lower than anticipated range on an 80% charge. I have not been able to determine why that is, and it could be significant. In the light of this, 85% usable on an 80% charge sounds a bit too high, and I'm curious if it will hold up in your testing. That said, I would be happy to make a Gid meter available to you if needed.

The Gids listed in the chart indicate top of the hour, which means that you should see a change on the charging time display at or around the referenced Gid count.

Overall, this approach works quite well, and I have heard from several folks who have adopted it, including couple of Leaf owners in Canada. The biggest problem I see is the fact the the charging time display will lose its point of reference if you use the trickle charger. That said, you can correct for that by applying an offset. Alternatively, you can top off to 80 or 100% on 120V, and the display will reset.

For example, I have received the low battery warning at 23 instead of 21 hours once. Knowing the correct value, I could see that the offset was approximately 2 hours, and the Leaf would be dead around 27 hours instead of the anticipated 25. This additional indicator can be helpful in the lower SOC reaches, if you don't have a Gid meter, and don't want to rely solely on mile counting.

I was looking at the the very nice charts surfingslovak's created and realized with all the battery degradation talk that we should also consistently see some reduction in estimated charge times that goes along with the reduction in battery capacity. Accordingly, as one adjusts the "Battery kWh usable" in the chart, one should also see a change in the time to charge.

For example - if a new car which reads ~281 GIDs on a 100% charge normally reads 21/17 hours to charge to 100/80%, compared to a Arizona car which has lost a capacity bar and is 15% down on capacity, one might expect the car to show 18/15 hours to charge to 100/80% on L1.

This might be a useful proxy for a GID meter for those who are waiting for LEAFSCAN or otherwise don't have a GID meter yet... This might be worth mentioning in on the capacity degradation threads...

I ran a range test, recently, and was able to go 64.5 miles from a 100% charge to LBW with 4.0 miles/kWh showing on the dash. This was on a day where the temperature was 78F with calm winds. Using the spreadsheet, I had to reduce the usable capacity down to 19.2 kWh to get things to match up. This value for usable capacity is pretty consistent with what I’ve seen on my daily commutes. At 39 miles, I start with 80% charge and either just lose the fourth bar, or just lose the third bar by the time I’m done, depending on how efficiently I can drive that day.

I haven’t looked at the time to charge numbers on the dash to see if they match the numbers in the spreadsheet. Since my usable capacity appears to be running about 8.5% less than what would be expected for a new battery, it should be interesting to see if the time to recharge numbers have also adjusted downward.

Today I drove 53.8 miles on a 80% charge averaging 4.6 m/kWh and got LBW around a mile from home. GOM=6 mi. Didn't check the charge timer. Charged for 34 minutes on L2 and drove another 11.7 miles (65.5 mi total for the day) and got LBW about 2.5 mi from home. Still showing 4.6 m/kWh and GOM=6mi. Charge timer shows 16/20 hours to 80%/100%, but according to the chart it should show at least 17/21 hours once you hit LBW.

Since I have to adjust available capacity on the chart to down to 17.6 kWh (!!!) to match the expectation of getting LBW on a 80% charge around mile 53 at 4.6 m/kWh, it makes sense that the charge timer will read low. Although if one assumes that 21 kWh is normal capacity and that my battery has really gone down to 17.6 kWh usable (which seems low to me) then the car should really show 18-19 hours to full.

The reason it seems low is that just less than 2 months ago I drove 49.5 mi @ 4.0 m/kWh without hitting LBW (GOM=9 mi). I have to adjust usable capacity to 19 kWh to achieve that. Of course, a week ago I drove 65.4 mi @ 4.3 m/kWh and got home w/GOM=8 mi - but no LBW. I have started recording time/energy from 80%-100% when I needed it and in the past 6 months (charged to 100% 4 times) it has declined from 88 minutes to 74 minutes and 4.96 kWh to 4.38 kWh.

Have to wonder if I've been afflicted by the recent decline in capacity loss that everyone else seems to be showing up in the last couple months even though I very rarely charge to 100% and average temperature is very moderate here (only recently started seeing 6 temp bars here during the day and usually falls back down to 5 bars by the morning), but at the same time I've always felt my car to be a kWh or 2 low in capacity... Really need a GID meter and to run a capacity test - perhaps my battery is simply out of balance since I rarely charge to 100% and have really avoided letting the car sit there for any period of time.

Also wonder what the time to 100% reports after a 80% charge - should we see 4h or 4.5?

drees said:

Also wonder what the time to 100% reports after a 80% charge - should we see 4h or 4.5?

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Dave, very interesting, thank you for all that data. To be clear, at 80% you should see 4 hours at 120V on the charging time display. I like your idea, and this could be potentially the easiest way to get some battery performance metrics:

1) Charge the Leaf to 80% or 100% on level 2
2) Connect the trickle cord and wait until it stops charging again (this should reset the charging time display and get rid of` any offset)
3) Drive the Leaf to the low battery warning (the first warning that appears)
4) Note the hours at 120V on the charging time display

Without a timer, a new car should be showing 21 hours at 120V right at the low battery warning. With a 80% timer set, this value should be 17 hours. Anything less than that, would indicate lower usable capacity. Each hour represents about 10 or 11 Gids or 4% of usable capacity. I'm validating this idea on my car right now, and if you wanted to help with this and see what you get on your Leaf, that would be great.

drees said:

Also wonder what the time to 100% reports after a 80% charge - should we see 4h or 4.5?

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I tried to see what my car would give and failed. On the Carwings website it tells me 3.5 hours, but this sometimes does not match the car's estimate. But when I got into the car to check the value there, it just gives me dashes. I tried turning off the 80% timer, but nothing changed. Can someone please give me a procedure to read this number from the car after an 80% charge on a timer? TIA!

RegGuheert said:

drees said:

Also wonder what the time to 100% reports after a 80% charge - should we see 4h or 4.5?

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I tried to see what my car would give and failed. On the Carwings website it tells me 3.5 hours, but this sometimes does not match the car's estimate. But when I got into the car to check the value there, it just gives me dashes. I tried turning off the 80% timer, but nothing changed. Can someone please give me a procedure to read this number from the car after an 80% charge on a timer? TIA!

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Reg, CarWings should show the time to a 100% charge, and disregard the timer. So this would be a good way of doing it. It's bit surprising to hear that it was showing 3.5 hours. It should be 4 hours even. I confirmed this many times over on my vehicle, and it seemed to have worked for several others. The dashes would seem to indicate that the 80% timer was active, and the SOC was above 80%.

Carwings showed 4h / 1:30 for me charged to 80% this morning as expected. I tried to get the car itself to show me time to 100% by turning off timers, changing my 80% timer to 100%, but for some reason the car itself wouldn't show anything but --.

drees said:

Carwings showed 4h / 1:30 for me charged to 80% this morning as expected. I tried to get the car itself to show me time to 100% by turning off timers, changing my 80% timer to 100%, but for some reason the car itself wouldn't show anything but --.

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Hm, that's interesting, and I wouldn't have an explanation for that I'm afraid. For what it's worth, I did a bit of testing this weekend, and confirmed your idea. I turtled at 24 hours today, one hour earlier than in December. This would be consistent with a 270 Gid reading on a full charge, whereas I always had 281 before. I hope to do some additional testing this week, but if someone with a lower Gid count could help validate the idea, and see if they turtled at 22 or 23 hours that would be great. Be sure to top off on 120V though to reset the charging time display.

surfingslovak said:

I did a bit of testing this weekend, and confirmed your idea. I turtled at 24 hours today, one hour earlier than in December. This would be consistent with a 270 Gid reading on a full charge, whereas I always had 281 before.

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281 GIDs / 25 hours = 11.24 GIDs/hour, so that definitely fits. It certainly looks like one can use deviation from your chart at low SOC as an estimate for 100% GID count. Think of it as the poor-man's GID meter.

surfingslovak said:

Be sure to top off on 120V though to reset the charging time display.

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Can you clarify what that does and when to do it?