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TonyWilliams
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 11:11 am

Ingineer wrote:There are a lot of factors that are needed to "accurately" calculate range. For instance, cooler denser air will increase energy consumption, so you have to take that into account as well. For the same reason that Nissan was unable to create an accurate range estimator, we also have that problem


Nissan didn't even include air density in their calculations, so to suggest they couldn't figure it out isn't quite accurate.

We can fly around the world and figure to within a very close tolerance air density. It's not rocket science anymore.

I use a simple rule of thumb on my chart of 1.5% increase in economy per thousand feet increase of density altitude. I also subtract 1% per 4F loss of battery temperature below 70F.

Hopefully with scan gauge, we can refine those.

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Nubo
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 1:33 pm

klapauzius wrote:...

In any case, "remaining kWH", regardless of the battery capacity etc, would be most helpful for me.


+1 for most of the time this is the number I'd be interested in. Expressed as "remaining watt-hours", would give plenty of resolution. Occasionally checking the "degradation factor" would be useful but for driving I just want to know how much "gas" I have in the tank -- not the percent of an idealized tank, or artificial units.
I noticed you're still working with polymers.

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Ingineer
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 2:22 pm

TonyWilliams wrote:
Ingineer wrote:There are a lot of factors that are needed to "accurately" calculate range. For instance, cooler denser air will increase energy consumption, so you have to take that into account as well. For the same reason that Nissan was unable to create an accurate range estimator, we also have that problem


Nissan didn't even include air density in their calculations, so to suggest they couldn't figure it out isn't quite accurate.

We can fly around the world and figure to within a very close tolerance air density. It's not rocket science anymore.

I use a simple rule of thumb on my chart of 1.5% increase in economy per thousand feet increase of density altitude. I also subtract 1% per 4F loss of battery temperature below 70F.

Hopefully with scan gauge, we can refine those.
I didn't suggest Nissan couldn't figure out how to add air density, I do however assert that Nissan couldn't figure out how to make an accrate range display. That system would really have to be psychic, or know the exact destination, route, traffic, and be in total control of the car. (Even then, it would still have some error)

What I'm saying is I don't want to try to make another inaccurate range display, I'll leave that calculation to the wetware upstairs. I want to give that wetware as much accurate information as I can at high resolution and at a fast rate.

-Phil
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klapauzius
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 2:26 pm

In order to see if the remaining kWH can be computed one would need the following:

1) charge the car to 100%, note the AH and pack voltage at full
2) drive around, record amps drawn from battery and current pack voltage e.g. every second
3) charge back to 100% and note the AH before charge and after and again keep track of the amps/voltage during charging.

I would assume during charging at least it should be straightforward to compute the energy put into the battery by integrating the charging amps times charging voltage. If that sums roughly up to the same integrated amps x voltage during driving, then the remaining energy could be computed, IF the energy at full was known....so once in a while one would have to repeat step 3) with an (almost) empty pack to keep track of the current max capacity.
For now we could assume 21 kWH for most packs?
In any case, if enough data was collected during driving, one could look for a relationship between integrated input power vs integrated output power, based on the instantaneous pack voltage/current draw/input

I am not sure if pack-voltage x amp hours at 100% full is a good indicator, since that voltage after charging stays not constant under load. But at least it puts an upper limit on max -capacity and maybe one can derive an average capacity correction factor based on individual driving habits?
Hopefully, that number wont fluctuate too much.

If anyone wants to post these numbers, we could see if a "remaining kWH" algorithm can be implemented...I guess it would need a lot of numbers to begin with...

klapauzius
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 2:32 pm

Ingineer wrote:Nissan didn't even include air density in their calculations, so to suggest they couldn't figure it out isn't quite accurate.

What I'm saying is I don't want to try to make another inaccurate range display, I'll leave that calculation to the wetware upstairs. I want to give that wetware as much accurate information as I can at high resolution and at a fast rate.

-Phil


I agree! I think a range estimator can be done by each driver, who knows the terrain in which he/she operates, but some estimate of the amount of energy in the battery would be helpful.

I wonder if the 12 bars that Nissan gives us are that, but I suspect not, since those bars scale with overall capacity.
I would really like a X kWH remaining number, although this might require some calibration of the overall battery capacity.

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TickTock
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 3:04 pm

klapauzius wrote:In order to see if the remaining kWH can be computed one would need the following:

1) charge the car to 100%, note the AH and pack voltage at full
2) drive around, record amps drawn from battery and current pack voltage e.g. every second
3) charge back to 100% and note the AH before charge and after and again keep track of the amps/voltage during charging.

I would assume during charging at least it should be straightforward to compute the energy put into the battery by integrating the charging amps times charging voltage. If that sums roughly up to the same integrated amps x voltage during driving, then the remaining energy could be computed, IF the energy at full was known....so once in a while one would have to repeat step 3) with an (almost) empty pack to keep track of the current max capacity.
For now we could assume 21 kWH for most packs?
In any case, if enough data was collected during driving, one could look for a relationship between integrated input power vs integrated output power, based on the instantaneous pack voltage/current draw/input

I am not sure if pack-voltage x amp hours at 100% full is a good indicator, since that voltage after charging stays not constant under load. But at least it puts an upper limit on max -capacity and maybe one can derive an average capacity correction factor based on individual driving habits?
Hopefully, that number wont fluctuate too much.

If anyone wants to post these numbers, we could see if a "remaining kWH" algorithm can be implemented...I guess it would need a lot of numbers to begin with...

Cetainly a good way to get confidence. However I don't think it is necessary. For my car, which is an outlyer, I get 80wh/gid. My max gids of 245 versus 281 for everyone else correlates really well to the 22kWh I measure from the wall versus 25kWh that everyone else sees. I had already estimated a gid=80wh for my car by logging the battery votlage and amps for several trips before Phil indicated that this was the standard. It is also very linear across the entire battery range. So, while you could go through all these steps to get better accuracy, simply multiplying by 80 should be good enough.

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TonyWilliams
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 3:31 pm

Ingineer wrote:
TonyWilliams wrote:
Ingineer wrote:There are a lot of factors that are needed to "accurately" calculate range. For instance, cooler denser air will increase energy consumption, so you have to take that into account as well. For the same reason that Nissan was unable to create an accurate range estimator, we also have that problem


Nissan didn't even include air density in their calculations, so to suggest they couldn't figure it out isn't quite accurate.

We can fly around the world and figure to within a very close tolerance air density. It's not rocket science anymore.

I use a simple rule of thumb on my chart of 1.5% increase in economy per thousand feet increase of density altitude. I also subtract 1% per 4F loss of battery temperature below 70F.

Hopefully with scan gauge, we can refine those.
I didn't suggest Nissan couldn't figure out how to add air density, I do however assert that Nissan couldn't figure out how to make an accrate range display. That system would really have to be psychic, or know the exact destination, route, traffic, and be in total control of the car. (Even then, it would still have some error)

What I'm saying is I don't want to try to make another inaccurate range display, I'll leave that calculation to the wetware upstairs. I want to give that wetware as much accurate information as I can at high resolution and at a fast rate.

-Phil


Even with the best Flight Management system, it still takes a little grey matter and experience to make it all work with airplanes, like it does every day, thousand of times per day, all over the world, in all weather, temperatures, weights, etc.

A computer is the best method to give us all the data, and processed data at that. I understand you don't want to do a range function, but computers don't need to be psychic to give a plausible solution. Your grey matter can determine to what degree that processed data is accurate.

Surely, you wouldn't suggest that computers that calculate range on existing equipment (if reasonably accurate) should be turned off to revert to grey matter calculating? I can assure you that aviation wouldn't then goes years between major crashes, like it does now.

So, to the LEAF. We all agree that the GoM is a piece of dog doo doo, and perfection is never going to happen, so I'll bet something in between is. You call that inaccurate; I call that a huge improvement.

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davewill
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 3:35 pm

I wish I could have a DTE that was simply based on my current displayed mi/kWh. Then I could reset the mi/kWh figure if I'm interested in knowing an "immediate" figure, or let it accumulate if that best meets my needs...of course if I had an accurate SOC, I could do the math in my head almost as easily.
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klapauzius
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 3:47 pm

TonyWilliams wrote:
So, to the LEAF. We all agree that the GoM is a piece of dog doo doo, and perfection is never going to happen, so I'll bet something in between is. You call that inaccurate; I call that a huge improvement.


I wonder if that ever has been corroborated by a real scientific study? While the range estimation is not very accurate at high levels of charge, once you have driven the car a bit, it becomes in my subjective (n-of-one) experience, quite accurate.

Again with automatic logging (or even pen and paper) it should be trivial to sum up actual miles driven + DTE and check how constant these numbers are over the length of the trip. If we do that across e.g. 100 drivers in different locations, we can easily compute a confidence level for the GOM and conclude if it is really dog-doo-doo or the innocent victim of prejudice...

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Ingineer
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Re: Real SOC (State of Charge) - Information

Mon Mar 19, 2012 6:12 pm

All we need to calc kWh remaining is the total pack amp-hour figure (67.568 on my car) and then correct that for the actual usable range, then multiply that by the SOC percentage to get amp-hours remaining, then multiply that by the current average voltage. Or, just display amp-hours directly and use that.

-Phil
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