Battery Capacity Gauge and Leaf Spy.

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andymcw1

New member
Joined
Jul 14, 2022
Messages
2
Hi,

I'm intrigued to know how the battery capacity gauge on the dash (up to 12 bars), relates to various battery parameters that can be measured on Leaf Spy. Does anyone know?
I've just bought a 6-year old 30Kwh Leaf with 62K miles on the clock. After a full charge the capacity gauge gives 11 bars (and 100% charge). But after driving a bit, the capacity gauge goes up to 12 and stays there. Can't work out what's going on there. On Leaf Spy after a full charge I'm seeing SOH = 80%, SOC = 96%, 288 GIDS, and Hx = 56%.
I want to be sure my dash gauge is reading right in case I have to invoke the 'below 9 bars' battery warranty in the next couple of years.

Thanks,

Andy
 
Welcome. The first/twelfth capacity bar represents about 15% of battery capacity, so when that 'drops' there is about 85% left. Most of the other bars are worth about 6% each, with the last bar being again worth more. When the gauge shows 8 bars remaining, and you bring the car to a dealer, they will apply the BMS firmware patch for a BMS display glitch. This will cause the BMS to reset, and for a few weeks you will again be seeing 12 capacity bars, until the BMS re-learns the actual capacity. When the gauge shows 8 bars again after that point, Nissan will replace the pack.
 
Thanks Leftiebiker.

I suspect I might already have the BMS patch.

I guess I was trying to figure out whether the capacity guage is directly displaying something like the SOH% that Leaf Spy shows. Is SOH a parameter that is generated by the BMS, or is it some internal calculation that Leaf Spy does?

I'm still confused why my capacity gauge goes back up from 11 to 12. Might the capacity improve as the battery warms up?

Thanks, Andy
 
The back and forth between 11 and 12 happens sometimes as the 12th bar fades. I think it indicates a very slow drop in capacity, as opposed to a faster one. The BMS communicates raw information, and that has been interpreted by the LeafSpy app according to the most logical equivalences - educated guesses. The gauge does pretty much the same thing, but was programmed by Nissan, so we know for sure that it is showing capacity - at least in the manner that Nissan wants it to be shown.
 
It is weird that LeafSpy reports SOH at 80% but the Leaf flips between showing 12 capacity bars and 11 bars. At that SOH, it should be 11 bars all the time.
 
Is SOH a parameter that is generated by the BMS, or is it some internal calculation that Leaf Spy does?

I think SOH is a parameter generated by the BMS and reported by LeafSpy. Like the 'Hx' reading which is also reported by LeafSpy.

I've never heard a definitive answer on how either one is calculated and I don't think anyone here even knows exactly what Hx means.
 
goldbrick said:
Is SOH a parameter that is generated by the BMS, or is it some internal calculation that Leaf Spy does?

I think SOH is a parameter generated by the BMS and reported by LeafSpy. Like the 'Hx' reading which is also reported by LeafSpy.

I've never heard a definitive answer on how either one is calculated and I don't think anyone here even knows exactly what Hx means.

Do a search, and you will find that longitudinal data indicate that on the GEN 1 Leaf's Hx is battery conductance,
decreasing with SOH, as has been noted a number of times on MNL.
 
goldbrick said:
Is SOH a parameter that is generated by the BMS, or is it some internal calculation that Leaf Spy does?

I think SOH is a parameter generated by the BMS and reported by LeafSpy. Like the 'Hx' reading which is also reported by LeafSpy.

I've never heard a definitive answer on how either one is calculated and I don't think anyone here even knows exactly what Hx means.
https://www.mynissanleaf.com/viewtopic.php?p=497564#p497564
https://www.mynissanleaf.com/viewtopic.php?f=44&t=14285&p=516444&hilit=nissan+meaning#p516444

Re: the bolded part, we'd need to hear some official acknowledgement, statement or documentation from Nissan about what Leaf Spy renders as SOH or Hx. AFAIK, there's been none, so all we can do is compare notes.

Some values that Leaf Spy renders can be verified like temps, tire pressures and voltages (https://www.mynissanleaf.com/viewtopic.php?t=17470).
 
cwerdna said:
goldbrick said:
Is SOH a parameter that is generated by the BMS, or is it some internal calculation that Leaf Spy does?

I think SOH is a parameter generated by the BMS and reported by LeafSpy. Like the 'Hx' reading which is also reported by LeafSpy.

I've never heard a definitive answer on how either one is calculated and I don't think anyone here even knows exactly what Hx means.
https://www.mynissanleaf.com/viewtopic.php?p=497564#p497564
https://www.mynissanleaf.com/viewtopic.php?f=44&t=14285&p=516444&hilit=nissan+meaning#p516444

Re: the bolded part, we'd need to hear some official acknowledgement, statement or documentation from Nissan about what Leaf Spy renders as SOH or Hx. AFAIK, there's been none, so all we can do is compare notes.

Some values that Leaf Spy renders can be verified like temps, tire pressures and voltages (https://www.mynissanleaf.com/viewtopic.php?t=17470).

Really? Surely some on MNL have the engineering background to gather Leaf data using LeafSpy/LeafDD and
infer what the data indicate, right? Here're battery resistance (mohms), increasing over time, data presented
numerous times on MNL from my Gen 1 Leaf ;

11/20/14 -13,700 miles, 76 mohms per LeafDD, 20 Deg, 73% SOC
11/27 -13,800 miles, 67 mohms per LeafDD. 25 deg, 63% SOC
11/30 - 13,900 miles, 56 mohms per LeafDD, 27 deg, 71% SOC
12/2 - 14.100 miles, 55 mohms per LeafDD, 28 deg, 67% SOC
12/16 - 14,500 miles, 89 mohms per LeafDD, 15 deg, 93% SOC
12/27/14 - 14,800 miles, 103 mohms per LeafDD, 11 deg, 24% SOC
3/10/15 - 17,400 miles, 60 mohms per LeafDD, 30 deg, 73% SOC
3/14 - 17, 550 miles, 56 mohms per LeafDD, 32 deg, 47% SOC
4/14 - 19,100 miles, 59 mohms per LeafDD, 25 deg. 38% SOC
5/4 - 19,989 miles, 64 mohms per LeafDD, 24 deg.  48% SOC
5/15 - 20,400 miles, 73 mohms per LeafDD, 20 deg. 41% SOC
5/22 - 20,700 miles, 58 mohms per LeafDD, 28 deg. 50% SOC
12/10/15 - 28,000 miles, 90 mohms per LeafDD, 19 deg. 92% SOC
4/5/16 - 32,000 miles, 74 mohms per LeafDD, 24 deg, 55% SOC
5/16 - 33,700 miles,89 mohms per LeafDD, 22 deg, 47% SOC
5/16 - 33.700 miles, 58 mohms per LeafDD, 31 deg, 76% SOC
10/5 - 39,300 miles, 100 mohms per LeafDD, 22 deg, 50% SOC
10/6 - 39,400 miles, 61 mohms per LeafDD, 30 deg, 51% SOC
10/7 - 39,500 miles, 80 mohms per LeafDD, 25 deg, 56% SOC
10/15/16 - 40,000 miles, 71 mohms per LeafDD, 27 deg, 45% SOC

Lowest Temp (11 degrees C) - 103 mohms - 15K miles
Highest Temp (32 degrees C) - 56 mohms - 18K miles

Lowest mohms - 55 (28 deg, 14K miles)
Highest mohms - 103 (11 deg, 15K miles)

Battery Aging Per Mileage - 55 mohms (28 deg, 14K miles), 71 mohms (27 deg, 40K miles)

Since conductance is the inverse of resistance, one can conclude that battery conductance (Hx) declines over
time with SOH as to be expected, i.e. a battery becomes less efficient - SOH declines.
 
I agree that SOH seems to be a pretty good measure of battery capacity. I also agree that on pre-2018 Leafs Hx seems to be an inverse of the battery pack's internal resistance. Hx on the 2018+ Leafs seems to be different.

The point I was trying to make is that the internal calculations are hidden and while we can say that SOH tracks capacity very well and Hx (pre-2018) tracks battery pack conductance very well, they are just values snagged from the CAN bus by LeafSpy and we don't know how they are calculated.

The 3 month 'adjustment' period and nearly linear drop in SOH vs time between adjustments seen on 2018+ Leafs could be explained by assuming some sort of model in the firmware that estimates the battery capacity and is updated periodically. But that's just a guess. We really don't know.

Automobile gauges aren't always what they seem. I've owned several VW Passats. The temperature gauge in these will indicate the coolant temperature to be 90C (needle straight up, in the center of its range) for quite a wide range of actual temperatures. Apparently this was done so that people didn't complain when their engine ran hotter while under a heavy load, like going up a hill. The actual temperature can be read from the OBDII port since the engine control firmware needs to know that but the display on the dash hides a lot of information.

On a Leaf, the GOM needs to know the battery capacity and the Hx could be used to calculate charging rates (?). But what Nissan decides to display on the dash is up to them.
 
goldbrick said:
I agree that SOH seems to be a pretty good measure of battery capacity. I also agree that on pre-2018 Leafs Hx seems to be an inverse of the battery pack's internal resistance. Hx on the 2018+ Leafs seems to be different.

The point I was trying to make is that the internal calculations are hidden and while we can say that SOH tracks capacity very well and Hx (pre-2018) tracks battery pack conductance very well, they are just values snagged from the CAN bus by LeafSpy and we don't know how they are calculated.

The 3 month 'adjustment' period and nearly linear drop in SOH vs time between adjustments seen on 2018+ Leafs could be explained by assuming some sort of model in the firmware that estimates the battery capacity and is updated periodically. But that's just a guess. We really don't know.
...
On a Leaf, the GOM needs to know the battery capacity and the Hx could be used to calculate charging rates (?). But what Nissan decides to display on the dash is up to them.
Bingo. We have no idea what Nissan intended these values to be or their caveats, accuracy, precision, necessary preconditions, etc. For all we know, Nissan might say something like you need to discharge to x% or dead and charge to full x # of times before this value is accurate. And, battery temp needs to be between x and y.
 
cwerdna said:
goldbrick said:
I agree that SOH seems to be a pretty good measure of battery capacity. I also agree that on pre-2018 Leafs Hx seems to be an inverse of the battery pack's internal resistance. Hx on the 2018+ Leafs seems to be different.

The point I was trying to make is that the internal calculations are hidden and while we can say that SOH tracks capacity very well and Hx (pre-2018) tracks battery pack conductance very well, they are just values snagged from the CAN bus by LeafSpy and we don't know how they are calculated.

The 3 month 'adjustment' period and nearly linear drop in SOH vs time between adjustments seen on 2018+ Leafs could be explained by assuming some sort of model in the firmware that estimates the battery capacity and is updated periodically. But that's just a guess. We really don't know.
...
On a Leaf, the GOM needs to know the battery capacity and the Hx could be used to calculate charging rates (?). But what Nissan decides to display on the dash is up to them.
Bingo. We have no idea what Nissan intended these values to be or their caveats, accuracy, precision, necessary preconditions, etc. For all we know, Nissan might say something like you need to discharge to x% or dead and charge to full x # of times before this value is accurate. And, battery temp needs to be between x and y.

Totally laughable! Then why even use any data from LeafSpy, or even monitor any battery data the Leaf displays.
 
Because we can glean useful information from it even though we can’t be assured of its universal truth.

lorenfb said:
Totally laughable! Then why even use any data from LeafSpy, or even monitor any battery data the Leaf displays.
 
91040 said:
Because we can glean useful information from it even though we can’t be assured of its universal truth.

lorenfb said:
Totally laughable! Then why even use any data from LeafSpy, or even monitor any battery data the Leaf displays.

It's hardly a mystery how the Leaf BMS most likely determines battery conductance (Hx). Some can still remember from
basis electronics that resistance (R) is equal to voltage (V) divided current (I), then R = V / I. Using differential calculus,
R = dV / dI, or R = (V1 - V2) / (I1 - I2). So to determine battery resistance;

1. The BMS A/D converter determines the needed parameters;
V1 is the no-load battery voltage, V2 is the voltage (new load) with a measurable current I differential,
e.g. when the AC compressor is activated.
2. The BMS processor chip then calculates the reciprocal of R to determine Hx (battery conductance),
and allows the Hx data to be read via a CAN using the OBDII connector with LeafSpy.

It appears you probably have disbelief in any technology you can't visually see how it functions, right?
 
It's hardly a mystery how the Leaf BMS most likely determines battery conductance (Hx). Some can still remember from
basis electronics that resistance (R) is equal to voltage (V) divided current (I), then R = V / I. Using differential calculus,
R = dV / dI, or R = (V1 - V2) / (I1 - I2). So to determine battery resistance;

1. The BMS A/D converter determines the needed parameters;
V1 is the no-load battery voltage, V2 is the voltage (new load) with a measurable current I differential,
e.g. when the AC compressor is activated.
2. The BMS processor chip then calculates the reciprocal of R to determine Hx (battery conductance),
and allows the Hx data to be read via a CAN using the OBDII connector with LeafSpy.

It appears you probably have disbelief in any technology you can't visually see how it functions, right?
[/quote]

Sorry but your math is a bit confused. Unless resistance R is an exponential function of I, its derivative does not equal itself. In other words the change in resistance is not equal to the resistance. Also a derivative involves a limit and so dV/dI is not equal to
(V1 - V2/(I1- I2). Are you just bringing calculus into your post to show that you do not understand derivatives.
 
lorenfb said:
91040 said:
Because we can glean useful information from it even though we can’t be assured of its universal truth.

lorenfb said:
Totally laughable! Then why even use any data from LeafSpy, or even monitor any battery data the Leaf displays.

It's hardly a mystery how the Leaf BMS most likely determines battery conductance (Hx). Some can still remember from
basis electronics that resistance (R) is equal to voltage (V) divided current (I), then R = V / I. Using differential calculus,
R = dV / dI, or R = (V1 - V2) / (I1 - I2). So to determine battery resistance;

1. The BMS A/D converter determines the needed parameters;
V1 is the no-load battery voltage, V2 is the voltage (new load) with a measurable current I differential,
e.g. when the AC compressor is activated.
2. The BMS processor chip then calculates the reciprocal of R to determine Hx (battery conductance),
and allows the Hx data to be read via a CAN using the OBDII connector with LeafSpy.

It appears you probably have disbelief in any technology you can't visually see how it functions, right?

It appears that your math is a bit confused. The derivative of resistance is not equal to the resistance itself unless the resistance is an exponential function of the current I. In addition, derivatives involve a limit so your expression (V1-V2/(I1-I2) is not the derivative. Why do you bring calculus into your post unless you want to show that you do not understand derivatives?
 
bmw said:
lorenfb said:
91040 said:
Because we can glean useful information from it even though we can’t be assured of its universal truth.

It's hardly a mystery how the Leaf BMS most likely determines battery conductance (Hx). Some can still remember from
basis electronics that resistance (R) is equal to voltage (V) divided current (I), then R = V / I. Using differential calculus,
R = dV / dI, or R = (V1 - V2) / (I1 - I2). So to determine battery resistance;

1. The BMS A/D converter determines the needed parameters;
V1 is the no-load battery voltage, V2 is the voltage (new load) with a measurable current I differential,
e.g. when the AC compressor is activated.
2. The BMS processor chip then calculates the reciprocal of R to determine Hx (battery conductance),
and allows the Hx data to be read via a CAN using the OBDII connector with LeafSpy.

It appears you probably have disbelief in any technology you can't visually see how it functions, right?

It appears that your math is a bit confused. The derivative of resistance is not equal to the resistance itself unless the resistance is an exponential function of the current I.

Where do you see a "derivative of resistance"? The expression (R = dV / dI) just defines how one typically determines
battery resistance, i.e. a change of battery output voltage divided a change of battery load current.

Battery resistance is typically determined by measuring the no load voltage (open circuit voltage) of the battery minus
the loaded voltage divided by the load current, R = (V1 - V2) / I1, where V1 is the no-load voltage, V2 is the loaded
battery voltage, I1 is the load current, and I0 (open circuit current - no load) is zero.

bmw said:
In addition, derivatives involve a limit so your
expression (V1-V2/(I1-I2) is not the derivative. Why do you bring calculus into your post unless you want to show
that you do not understand derivatives?

Again, R can be defined as a change of voltage divided a change of current, so R = (V0 - V1) / (I0 - I1) or R = dV / dI.
One can also correctly express a change of voltage as, dV = R * dI, or this, dV = (I / C) * dT.
 
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