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planet4ever said:
AndyH said:
Cross-checking with the Owners Manual, it appears that the 'battery low' warning light activates when the pack reaches 4kWh remaining
Agreed.

AndyH said:
and that's the power reduction threshold.
Huh? No way! Power reduction is when the turtle light comes on, formally known as the 'power limitation indicator light'. That's a completely different light from 'battery low warning light'.

AndyH said:
It also appears that's when the last bar goes dark - 16.25% remaining from a 24kWh hour pack is 3.9kWh.
Umm ... Andy, you were looking at the wrong table. 16.25 is in the Capacity table, not the Available Charge table. If I am reading the table correctly, the last red bar turns off when the available charge drops to 4%, i.e. about 1 kWh left.
Nice job - thanks! Sometimes a little bit of info is dangerous... Let's try this again...once reviewed 'll edit the original.

bg6.jpg


12 - Driving Range Display
13 - Battery Available Charge Gauge (Fuel Gauge)
14 - Battery Capacity Level Gauge (Battery Condition/Total Capacity Gauge)

The inner gauge is the 'Battery Available Charge Gauge'.

bg3.jpg


bg4.jpg


bg5.jpg


bg7.jpg


Ok, my head hurts now. The low battery charge warning light (fuel pump) activates when we discharge the pack to 4kWh (16.7% capacity) or less. How many Available Charge Gauge bars are lit at that point? And the timing table - do bars represent different states of charge during discharge and charge? What's with the 4% 'missing' between bars? (As an aside, the EVC section says the low charge warning light extinguishes when the pack has recovered 4.5kWh or more energy.)

The turtle light...Power Limitation Light...will illuminate when the battery level is low (but how low?), or when the battery can provide 40kW or less power, or when the motor or inverter is overheated, or the pack temperature is too high or too low, or battery capacity is low, or... (EVC p.53)

bg6.jpg


12 - Driving Range Display
13 - Battery Available Charge Gauge (Fuel Gauge)
14 - Battery Capacity Level Gauge (Battery Condition/Total Capacity Gauge)

bg1.jpg


bg2.jpg


This gauge loses bars as the battery degrades. It looks like this is a joint BMS and car controller function.
 
AndyH said:
bg6.jpg


12 - Driving Range Display
13 - Battery Available Charge Gauge (Fuel Gauge)
14 - Battery Capacity Level Gauge (Battery Condition/Total Capacity Gauge)
As Fonzie used to say, "I knew that." Sorry. Clearly anything I said or anyone else said about the two red bars was nonsense. Maybe I'll feel differently once I'm driving my LEAF, but at the moment the display seems counter-intuitive, as if the most obvious part (capacity) is the part we need to pay little attention to while driving.

AndyH said:
Ok, my head hurts now. The low battery charge warning light (fuel pump) activates when we discharge the pack to 4kWh (16.7% capacity) or less. How many Available Charge Gauge bars are lit at that point? And the timing table - do bars represent different states of charge during discharge and charge? What's with the 4% 'missing' between bars?
As someone pointed out earlier, the 4% is so the bar doesn't flicker on and off when at the transition point. If I'm reading the table correctly, at 16.7% there will be two bars lit. When the charge drops to 12% one of those two bars will go out. If you pick up some regen juice and get back up to 14% you will still see only one bar. You have to get back up to 16% to see the second bar.

AndyH said:
The turtle light...Power Limitation Light...will illuminate when the battery level is low (but how low?), or when the battery can provide 40kW or less power, or when the motor or inverter is overheated, or the pack temperature is too high or too low, or battery capacity is low, or... (EVC p.53)
Clearly there are multiple conditions that can cause this to come on, and they are all sort of "emergency room" situations. But as for the available charge case, my guess is at 4%, the same point where the last bar disappears. However, evnow could be right that it is more like 8%. I lean toward the lower figure since someone reported that they "believed" they had traveled about 10 miles after the battery charge warning came on, and they hadn't seen the turtle light yet. It also seems to me that you are going to get (be forced to get) very high mileage in turtle mode; probably at least 7 miles/kWh. I would think that 5 miles in that mode would be about all that anyone could tolerate. So why force it with more than 1 kWh left?
 
Here is my interpretation of the "Battery Available Charge Gauge (Fuel Gauge)" and the "Li-ion battery available charge gauge segments ON/OFF parameters"

Looking at the chart there is two thresholds for the illumination of the 12 bars. The ON timing threshold is used when energy is going into the battery pack such as charging or regen breaking and the OFF timing threshold when energy is going out of the pack such as driving the wheels or running the climate control.

So if I was to look at the gauge and I saw it change from 10 bars lit to 9 bars lit according to the chart the battery would be at 76% of capacity and assuming a 24kWh pack that would come out to 18.24kWh.

Now I just happened to reach the peak of a long hill when that 10 bar turned off so I will now be putting energy back into the battery by using regen breaking but it won't be until the battery is 80% charged or about 19.2kWh before the 10 bar is lit again.
 
evnow said:
My reading.
- Battery low when 2 bars are lit (4kwh)
- Turtle when one bar is lit (2kwh)
I see from the images in this thread that the mileage indicator will start blinking at 4kWh remaining and go to "---" at 2kWh remaining but I did not see where turtle mode kicks in. If I had to guess it would be at the no bars threshold or 4% or about 1kWh of the 24kWh usable.
 
I hope I am not stating the obvious but here is a little math using the chart and assuming 24kWh usable pack. This is assuming the battery is discharging
Code:
12 bars lit 100% to 92%  24.00 kWh to 22.08 kWh
11 bars lit  92% to 84%  22.08 kWh to 20.16 kWh
10 bars lit  84% to 76%  20.16 kWh to 18.24 kWh
09 bars lit  76% to 68%  18.24 kWh to 16.32 kWh
08 bars lit  68% to 60%  16.32 kWh to 14.40 kWh
07 bars lit  60% to 52%  14.40 kWh to 12.48 kWh
06 bars lit  52% to 44%  12.48 kWh to 10.56 kWh
05 bars lit  44% to 36%  10.56 kWh to  8.64 kWh
04 bars lit  36% to 28%   8.64 kWh to  6.72 kWh
03 bars lit  28% to 20%   6.72 kWh to  4.80 kWh
02 bars lit  20% to 12%   4.80 kWh to  2.88 kWh  Low battery and charge warning and range blinking at 4 kWh  
01 bar  lit  12% to  4%   2.88 kWh to  0.96 kWh  Range displays "---" at 2 kWh and turtle mode suspected
00 bars lit   4% to  0%   0.96 kWh to  0.00 kWh
Hopefully this will help with the discussion. Does it make sense?
 
]I think you will get battery low at 2 bars. Anyway - it will be a good test.[/quote said:
I got low batt yesterday as I pulled into my garage with 14 mi left with 2 of 12 bars (the red 2)

Malcolm :geek:
 
Although the BMS can measure the net kWh leaving the battery since it was last charged, and could do this quite accurately, it has only an inaccurate ESTIMATE of the Pack's SOC, obtained from measuring the voltages on the cells, and probably using the lowest cell's voltage to ESTIMATE that cell's SOC.

Sure, it might calculate a 87.1% SOC from a 3.52v reading, but the actual SOC is probably +/- 5% of that "calculated" value. While driving and current out of the pack is fluctuating substantually, it is even difficult to "calculate" the cell's "resting" voltage, since each cell's internal "resistance" will vary with age, temperature, and current flow rate. Sure, averages can be used to create estimates of the "resistance", and those estimates used to calculate an estimate of the cell's resting voltage from an in-use measured voltage, and that value used to "approximate" the cell's SOC, assuming it is a cell with "typical" characteristics.

So, the calculated SOC is not accurate at all, just an approximation.

Yes, you can know that you have used 13.15 kWh from the cells, but you really have no way of telling exactly how full the pack was when you started measuring, or where the "bottom" of the pack (weakest cell) will be until you actually get there.

Perhaps the "yearly" test is a "fill-drain-and-refill" test?
 
garygid said:
Sure, it might calculate a 87.1% SOC from a 3.52v reading, but the actual SOC is probably +/- 5% of that "calculated" value.

Shhhh ! Didn't you read how important it is to display the soc to 0.1% ?
 
OK, here's what happened.

Left home at 83% charged with 86 miles range, and arrived at the office 50% charged and with 48 miles of range. BTW, that's the same 33% discharge from the previous 2 days!

83_percent.jpg

50_percent.jpg


Underestimated a bit what I would get in terms of miles per bar - I had reckoned 6.6 miles but actually got 6.8 miles @ ~4mpkWh, and a hair better when my consumption went up to ~4.3mpkWh. As you can see from the first two photos - 6.8 miles for each of those exactly. Photo three (20.7 miles) might have come a bit late....was focused more on the truck in front of me at the time. But by photo four (28.2 miles), which is the point at which I went from 7 bars to 6, you can clearly see that I'm doing ~7 miles per bar.

9_bars.jpg

8_bars.jpg

7_bars.jpg

6_bars.jpg

6_bars_dest.jpg
 
garygid said:
It appears that the Capacity Bars do not even WARN you of any CAPACITY loss until you have LOST 15% (down to 85%), presumably of "usable" capacity.

The capacity loss thresholds are as they are. One point is that the 'fuel gauge' function varies and is affected by both pack temperature and usable capacity. We can gain another 'fuel gauge' bar sitting in the driveway if the pack cools and loses overall capacity.
 
I think that much granularity would confuse many. 80, 90 and 100 would be nice however. It should be noted, though, that unless these batteries are substantially different form lithium batteries in general, charging to 100 percent does less long term damage to a batter than discharging to 10 percent or less. So, if you are routinely getting home with the low battery light on or close to it when you charge to 80 percent, you are likely better off in the long run going to 100 percent.


Gonewild said:
I would like Nissan to add more % like 80% 85% 90& 100%
 
Gary, let's take this apart. I'd like to understand what you're trying to say here.

garygid said:
Although the BMS can measure the net kWh leaving the battery since it was last charged, and could do this quite accurately,...
The car has three current sensors installed. One is in the pack and measures energy coming in and out. I haven't positively identified the other two, but have seen CAN bus messages that report regen energy flow from the inverter, and charger current, so expect the other two current sensors are in or near those systems. This suggests to me that we can get a pretty accurate count of energy movement and sources. (Let's ignore small tolerances this time around...)

garygid said:
...it has only an inaccurate ESTIMATE of the Pack's SOC, obtained from measuring the voltages on the cells, and probably using the lowest cell's voltage to ESTIMATE that cell's SOC.
I expect the phrase 'inaccurate estimate' wasn't intended to communicate 'measurement confidence'. ;) Here's a place I don't agree. Here's why.

Voltage isn't a direct measurement of state of charge (SOC) but we have had plenty of time with lead-acid batteries and have been able to accurately estimate state of charge from the voltage (with a temperature allowance). We've been able to do that because lead-acid has a sloped discharge curve. The red line shows a constant current discharge curve from a sealed lead acid battery. The black line is the discharge curve from a LiFePO4 battery under the same conditions.

LiFePO4_vs_PBA_10A_800.jpg


Please note the downward slope of the lead-acid battery VS. the flat discharge of the LiFePO4 battery. We cannot measure SOC from LiFePO4 until the cell is nearly completely charged or nearly completely discharged - but we can track lead-acid's SOC throughout the entire charge or discharge.

Here's where you say "why should I pay attention to this nonsense - we don't use lead-acid or LiFePO4 in the Leaf!" - and you're right. Here's why it's important to see two examples of the SOC measurement problem:

EIG_LiMn_discharge.jpg


This is a series of constant current discharge charts from a laminated LiMn2O4 cell - just like we use in the Leaf. The discharge slope is more dramatic than lead-acid.

I hope you can see that we can get a pretty good estimate of SOC from LiMn2O4 - and likely a more accurate determination than lead-acid due to the steeper slope.

garygid said:
Sure, it might calculate a 87.1% SOC from a 3.52v reading, but the actual SOC is probably +/- 5% of that "calculated" value. While driving and current out of the pack is fluctuating substantually, it is even difficult to "calculate" the cell's "resting" voltage, since each cell's internal "resistance" will vary with age, temperature, and current flow rate. Sure, averages can be used to create estimates of the "resistance", and those estimates used to calculate an estimate of the cell's resting voltage from an in-use measured voltage, and that value used to "approximate" the cell's SOC, assuming it is a cell with "typical" characteristics.

So, the calculated SOC is not accurate at all, just an approximation.
I see a couple of concerns here. First, we know that the car is aware of current into and out of the pack. We know it's aware of ambient temperature from the front bumper sensor, and of pack temperature from the four temp sensors in the pack. We know that the car's battery controller monitors and logs individual cell degradation and cell internal resistance. We don't pull energy from an EV pack the way a bench test can maintain a constant discharge current - but we also don't spent the entire 2-hour drive with our foot on the floor. There are plenty of places in the drive where we have true 'resting voltage' to measure. And since the car is aware of and actively using all of the other parameters necessary, it can continue to model and track the discharge. So no - I absolutely do not agree with what appears to be an attempt to suggest any attempt to estimate SOC while in motion is 'voodoo.' ;)

garygid said:
Yes, you can know that you have used 13.15 kWh from the cells, but you really have no way of telling exactly how full the pack was when you started measuring, or where the "bottom" of the pack (weakest cell) will be until you actually get there.

Perhaps the "yearly" test is a "fill-drain-and-refill" test?
We've talked about this before, Gary (including the charts - I reported this back in May) and while I agree that the "actual" SOC and the "car's SOC log" can diverge over time, I've studied the GM EV1/S10 system and the Ranger EV system. I think the Leaf's battery monitoring system is a significant improvement over the other two - and over ANY of the monitoring or management systems available to the do-it-yourself market. While I desire truth more than ego or post count, and will absolutely accept being proven wrong when we get more real-world experience with the car, I don't think our SOC numbers are going to be that far off. Pizza bet time? ;)

I've not seen anything in the manuals that suggest that the annual pack test includes either a discharge or recharge. The car's systems track each cell and the pack health report can be generated in seconds by downloading the data from the car. The only time cells are charged or discharged is when cells and/or modules are replaced in the pack.

SOC is directly reported and available on the CAN bus, as are cell condition variables like internal resistance, voltages, pack temperature and the rest. Time will tell.

edit...fixed link
 
mogur said:
It should be noted, though, that unless these batteries are substantially different form lithium batteries in general, charging to 100 percent does less long term damage to a batter than discharging to 10 percent or less.
What you say is absolutely true - charging or discharging completely will take cycles off the cell's life. But as end-users we do not have to worry about this because Nissan will not let us get into the end-zones that negatively impact pack life. We can't get there - therefore we cannot put ourselves in danger and therefore cannot protect ourselves from it.

We must stop trying to bend the spoon - there is no spoon!

spoon.jpg
 
AndyH said:
mogur said:
It should be noted, though, that unless these batteries are substantially different form lithium batteries in general, charging to 100 percent does less long term damage to a batter than discharging to 10 percent or less.
What you say is absolutely true - charging or discharging completely will take cycles off the cell's life. But as end-users we do not have to worry about this because Nissan will not let us get into the end-zones that negatively impact pack life. We can't get there - therefore we cannot put ourselves in danger and therefore cannot protect ourselves from it.

We must stop trying to bend the spoon - there is no spoon!

spoon.jpg

So do you recommend to go ahead and charge to 100% (per the car display) every night without worry since is not really "100%"?
 
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