Real SOC (State of Charge) - Information

[copdoc]

<snip>If the "fuel" value shown always goes to 100%, even after the battery loses capacity, that is also misleading for calculating range. If the battery has lost 7.6%, I would want my "full" fuel gauge to show 92.4% (percentage of New-Battery usable "fuel", or energy).</snip>

+1 Seems like this will go hand-in-hand with Tony's range chart to give really accurate predictive capability ... but not if it changes over time.

(or perhaps I'm confused.....)

[surfingslovak]

Where are you getting these SOC values? Again, Gary's box only shows watt-hours, not SOC.

Phil, LEAFfan is using a modified, or prototype, ScanGauge in his car. As far as I know, it's reading the same CAN bus code Gary does.

[Ingineer]

The problem with using the watt-hours number is resolution. If you are happy with the ~280 step gauge, then by all means you can continue to use that on LEAFSCAN. However it's not for me, as I love seeing the SOC numbers tick down during my drive, and the 5 digit resolution is enough to even instantly see the effect using the climate control has on remaining energy. The "Gids" are just not a high enough resolution for me!

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. Seeing exactly how much energy is currently being used at all times and seeing how quickly your actions behind the wheel suck the pack dry allows your wetware upstairs to get a really good feel for range and also makes you a more efficient driver.

If someone can devise a good formula for displaying the usable energy in a higher resolution, I'll be happy to implement it. Maybe we can take the current capacity figure (amp hours with precision to the thousandths) and multiply that by corrected SOC and get a higher resolution watt-hours figure that both represents real energy (that will degrade over time) so you can "feel" it tick down.

-Phil

[edatoakrun]

Based on suggestion, I may add an expanded SOC variable that actually runs from 0% to 100% rather than 2% to 95%. The roughly 7% gap is what Nissan decided should not be used for longest life on the battery pack. Last time I checked, my Leaf was reporting 67.568 amp-hours full capacity.

-Phil

Phil-

What variability of battery capacity are you seeing, with battery temp changes only?

I don't think capacity loss over time will be too great a problem for a driver watching a % of capacity display, as an indication of available range, since this will occur slowly, over years.

But if battery capacity changes significantly due to battery temp, the % could be misleading for range purposes, from day to day, or even over a single day, even for drivers capable of using "wetware".

[garygid]

I believe LeafFan shows the same data that the "SOC-Meter" (GID-Meter) shows:

GID = EV:5BC:D1 and top 2 bits of D2 (of D1-D8)
And, the "soc" or "gid" percent = 100.0% * (GID / 281)

There should be no confusion about where the GIDs and GID% come from, but just a question of what it REALLY means, in spite of the 80 Wh description.

Only a few times have cars reported over 281, sometimes associated with a QC session.

Many cars have reported 281 occasionally, but most report slightly less (oftenvin the mid to high 270's).

A few cars (like TickTock's) report significantly lower values after a "100%" charge.

While watching digits whirl down, it is not possible for most people to get meaningful information, at least quickly. That is why we show significant rate-of-change meters: Wh/minute, Wh/mile, or Miles/kWh.

Hopefully the LS will be able to show both integrated (quantity from a starting-point from a rate) and differentiated (rate from a changing quantity) derived values.

Also, showing 0.001% value changes on a value that is unlikely to be accurate to 1%, would appear to be just a fun game, not really very useful IMO.

But, the ability to modify or ignore the "standard" screens and create one's own screens will allow a LOT of flexibility, especially if the last-seen screen (or a user-selected default screen) is displayed at boot-up.

Please keep up the great work.

[klapauzius]

For my internal range estimate I try to guess the remaining kWH in the pack, which
combined with the Miles/kWh measure on the dash works reasonably well...So if you
can display the kWH remaining, that would be great.

Since you have the remaining Ah it should be possible, although I dont know how much the voltage under load varies and how reliable integration of current amps*voltage would be? Maybe averaging over a few seconds will make it stable enough, but then I guess that is what the built-in SOC meter is doing anyway?

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

[TickTock]

For my internal range estimate I try to guess the remaining kWH in the pack, which
combined with the Miles/kWh measure on the dash works reasonably well...So if you
can display the kWH remaining, that would be great.

Since you have the remaining Ah it should be possible, although I dont know how much the voltage under load varies and how reliable integration of current amps*voltage would be? Maybe averaging over a few seconds will make it stable enough, but then I guess that is what the built-in SOC meter is doing anyway?

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

+1

[garygid]

I could easily display GIDs * 80 / 1000 = "kWh" (like "E24.8"),
as a 3rd value in Mode 1, but I think the resulting Energy
value is substantially misleading.

So far I have not seen any evidence that 80 Wh per GID
actually represents the USABLE Energy, but there appears
to be some evidence that it does not accurately do that.

Without knowing how the car measures, corrects, and thus
derives the GIDs, the value should be used with educated caution.

If I put this "E" feature in, I might need to use a multiplier lower than 80, and possibly make it user-adjustable.

Suggested values?

[TonyWilliams]

A MUCH more useful figure would be the Pack's usable-energy Capacity as a percentage of New-Battery (and in kWh). Right now, Nissan "hides" that dapacity-loss information until 15% is gone - MUCH too late to modify usage habits to better preserve the Pack Capacity.

Gary,

I think Phil said his unit will display the accurate loss of battery capacity (not the dumbed down 15% loss equals a bar).

With that data, shouldn't a remapped SOC at 100% (real 95% SOC) times a ten percent loss of capacity equal about 90% Gid that we expect to see (with the 10% capacity loss)?

I think we'll have enough data now (with battery temp also) to give a real world value of remaining kWh multiplied by miles/kWh equals how far you'll go in existing conditions.

Exciting times,

Tony

[TonyWilliams]

If I put this "E" feature in, I might need to use a multiplier lower than 80, and possibly make it user-adjustable.

Suggested values?

I thought we already had a good ballpark at 73.