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TonyWilliams
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Sun Sep 22, 2013 12:08 pm

surfingslovak wrote:
TonyWilliams wrote:I believe the current LEAF Spy app display of kWh is merely Ah * nominal voltage (sorry, I'm not sure of the exact method of calculation since if it's not useful data for range estimation, I really don't care how it's calculated).

That has changed. Since Jim was able to get real GIDs off the CAN bus, he is using 80 Wh per GID to calculate the total stored energy. I did not use the app recently to tell you if battery charging and discharging efficiency is taken into account, but Jim confirmed above that he has implemented temperature correction. He also subtracts the fixed reserve at the bottom. I believe that it's user adjustable, and one can select how much reserve should be loped off the indicated stored energy. I think Jim needs to be lobbied to changed the GID multiplier from 80 to something else. Perhaps this could be exposed as an adjustable value in the preferences as well? That could be more easily understood than a battery efficiency factor, which was proposed earlier.


We're making progress then!!

Yes, a very simple user adjustment of 75 to 80 watt/hours per Gid in 0.5 increments would finally get all DTE and kWh data compatible. I would have it DEFAULT to 77.5

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garygid
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Mon Sep 23, 2013 7:33 am

I thought that the 80 Wh was the energy applied to the battery,
and less is actually stored in the battery. Then, less than that is
available, since there are losses when extracting energy from
the battery, just as there are losses when filling the battery?

So, maybe something like 78 is stored and 76 is actually recovered for use?

Just asking TMWK (the man who knows).
Thanks, Gary
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TonyWilliams
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Mon Sep 23, 2013 8:22 am

garygid wrote:I thought that the 80 Wh was the energy applied to the battery,
and less is actually stored in the battery. Then, less than that is
available, since there are losses when extracting energy from
the battery, just as there are losses when filling the battery?

So, maybe something like 78 is stored and 76 is actually recovered for use?

Just asking TMWK (the man who knows).
Thanks, Gary


The 80 value checks out perfectly against the government battery measurements. At 22.031kWh from the charger to the battery, plus the absolute likely minimum of 0.300kWh to 0.400kWh still in the battery, the total divided by 281 Gid equals 79.47 to 79.83 wattHours each.

Of course, we don't know that the government test actually showed 281 Gid. Just 280 Gid would put the value at 79.75 to 80.11. So, I'm glad we have non-Nissan lab results to back up our data.

The 21.381kWh actually recovered means there is a direct battery energy recovery loss of 21.381 / 22.031, or 97.05% efficient.

If we apply that 97.05% in this example to 80 wattHours, it becomes 77.64 per Gid for "energy from the battery during discharge".

Since they did this all in a lab at room temperature, it's perfect data to apply temperature correction factors to. But, the above example is why I chose 77.5 per Gid as the default. GIDs continue to be the gold standard for determining the only thing the end user cares about; usable capacity for range.

That usable battery capacity, with temperature correction and compensated for UNusable energy will generally align with the dash miles per kWh economy meter to get ultimate range.

The displayed kWh on the LEAF Spy app should reflect this data. Conversely, we get exactly the same ultimate result with continuing to call a Gid = 80 with a 97.05% correction factor.

Now, the app would show a 281 Gid battery at 70F temperature to have:


(((281 - 6 UNusable) * 80) * .9705 energy recovery factor) * 0% temp correction = 21.351kWh usable


Isn't is great how all that works out?

When the car is being driven at 4.1 miles per kWh, the DTE value in the app will show:


4.1 * 21.351 = 87.5 miles, or just about EXACTLY what it will actually do.


LEAF battery capacities

Energy from the wall from dead to 100%: 25.414 kWh
Energy from the onboard charger to battery: 22.031 kWh (86.6% charger efficiency)
Energy from the battery during discharge: 21.381 kWh (our generic "21kWh" useable at 70F)

http://www1.eere.energy.gov/vehiclesand ... 2012_o.pdf

http://www1.eere.energy.gov/vehiclesand ... 2012_p.pdf

GregH
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Tue Sep 24, 2013 10:26 am

Why 281? The 2013s go to 284.. And shouldn't this discussion be in one of the many Gid or kWh threads and not active CAN sampling?
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TonyWilliams
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Tue Sep 24, 2013 2:12 pm

GregH wrote:Why 281? The 2013s go to 284.. And shouldn't this discussion be in one of the many Gid or kWh threads and not active CAN sampling?


Well, 281 has been the typical highest value for most LEAFs, including the 2013 that I tested March 2013. Yes, there have been 2011-2012 that have had 282 and 283 (I don't think I've ever heard of 284), and many reports of 284 on the 2013 LEAF. 281 is the number that stuck. If you get 284, congrats, that might be worth almost another mile in range. With any app that would multiply the miles/kWh from the dash by the Gid with correction factors, that extra mile of 284 will be reflected in the range estimate.

I've been writing about this so long that I'm confident that you could find some variation of what I posted above in just about any pertinent thread in this forum. That includes from the very first time that Ingineer officially told us that a Gid was 80 watthours (well, it was actually disclosed at the Dec 3, 2011 Nissan Love-Fest at Google headquarters, which I attended). I disputed the 80 value then, explaining that just because Nissan says 80 doesn't make that useful for the end user for range calculations or available usable capacity.

I prefer accurate data, and I also want to accurately know how far I can drive.

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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Mon Jan 06, 2014 9:51 am

With the help of a few LeafDD customers in colder climates, we can now extend the temperature translation table (first post of this thread) down to 0C.. and soon hopefully confirm down to -10C..
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Mon Jan 06, 2014 10:50 am

GregH wrote:Why 281? The 2013s go to 284.. And shouldn't this discussion be in one of the many Gid or kWh threads and not active CAN sampling?

Is there a special trick to make it go to 284?
I've never seen more than 256 in mine.

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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Mon Jan 06, 2014 11:09 am

GregH wrote:With the help of a few LeafDD customers in colder climates, we can now extend the temperature translation table (first post of this thread) down to 0C.. and soon hopefully confirm down to -10C..

Very nice! These remain surprisingly linear - looks like extrapolation should be valid outside this range.
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Mon Jan 06, 2014 11:23 am

Tomasz wrote:
GregH wrote:Why 281? The 2013s go to 284.. And shouldn't this discussion be in one of the many Gid or kWh threads and not active CAN sampling?

Is there a special trick to make it go to 284?
I've never seen more than 256 in mine.

Ha! Now there's a can of worms.. In olden times, the MNL Elders thought the highest possible Gid reading was 281 and thus many equations were postulated to calculate true SOC or capacity. Not really one to say "told ya so" (well ok, maybe) but of course newer batteries might well have slightly higher capacity or new software might tweak it to give slightly higher numbers. Sure enough SOME 2013 packs report 284. Oddly other new 2013s are surprisingly lower, but that's another topic. In the future we might get Leafs that go up to 300 Gids or beyond (we can only hope, right?)

Anyway.. the debate between SOC and remaining energy as far as best thing to gauge rages on.. Personally I'm dabbling with capacity*soc (reported as Ah, 4th option on LeafDD page 1), although I still like plain old raw Gids... Both of which might be considered remaining energy rather than SOC btw.

Rambling on and getting more philosophical.. What is "State of Charge" anyway? Who says it needs to be a % of full? Maybe remaining energy (be it Gids or Ah) is a better "State of Charge" anyway.
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Re: Active EV-CAN sampling: cell voltages, pack temperatures

Mon Jan 06, 2014 11:27 am

TickTock wrote:
GregH wrote:With the help of a few LeafDD customers in colder climates, we can now extend the temperature translation table (first post of this thread) down to 0C.. and soon hopefully confirm down to -10C..

Very nice! These remain surprisingly linear - looks like extrapolation should be valid outside this range.


I know! Personally I'm shocked it's still 10 clicks per degree C all the way down to 0C.. I would have thought for sure the nonlinearity of the thermistor would have resulted in 12 or 13 clicks per degree C down in the colder realm (as it is confirmed 8 or 9 on the hot side). Could it be the Leaf's own temperature calcs are lazily linear? And in the end, do we care what the real temps are or what the trigger points for things like temp bars and battery heaters is?
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