Alternative Approach to Battery Health Check

I monitor my battery via LeafSpy once a month, but the effect of battery temperature and perhaps less than stellar instrumentation in the LEAF prompted me to cook up another, distance traveled method as a x-check. This one depends on the accuracy of the battery SoC and the consumption meter. Since my readings will occur after I have used at least half of the battery capacity each time I hope for reasonable accuracy*.

Method:
Set trip meter to zero
Set consumption meter to zero
Charge to 100%
Drive to work (45 miles), note SoC drop(1)
Charge to 100%
Drive home (45 miles), note SoC drop(2)
Note consumption meter (CM) after 90 miles

kWh consumed = 90 miles / CM

* The CM has only one sig digit, so the result is ~ +/- 1%

100% battery capacity = kWh_consumed / (SoC_drop_1 + SoC_drop_2)

I wonder the benefit of keeping such an eagle eye on your battery. Sorry, but I don't see the need to worry about this... I do a Leafspy about once every 6 months of so for giggles

I kind of see it the same as someone who is counting down how many days of life they have left before you die..

You really cant do anything about it, and when it happens, you will know how long your battery lasted... Then it is time for a new one.

...

powersurge said:

I
I kind of see it the same as someone who is counting down how many days of life they have left before you die..

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Not a bad analogy. Lifestyle choices make a HUGE difference to quality of life and group longevity.
Have you ever noticed the US Surgeon General's warnings to not get fat and sedentary, and to avoid tobacco ?

No need for you to apologize, or post in this thread. It is directed towards people who want to know the battery health of the car.

powersurge said:

You really cant do anything about it, and when it happens, you will know how long your battery lasted... Then it is time for a new one.

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Complete bull.

There are plenty of steps one can take to increase longevity besides moving to a cooler climate, such as limiting time at high state of charge, parking in cooler areas and out of the sun, limiting time at high battery temps.

If you had started following Leaf back at the beginning and lived in a hotter climate, perhaps your tune would be different.

The problem I see with this approach is that it doesn't correct for headwinds or tailwinds, or for that matter, air density at different temps. I assume you use it only when you are alone in the car. You can probably see changes in capacity in maybe 5-10% increments this way, but not much less than that.

cwerdna said:

powersurge said:

You really cant do anything about it, and when it happens, you will know how long your battery lasted... Then it is time for a new one.

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Complete bull.

There are plenty of steps one can take to increase longevity besides moving to a cooler climate, such as limiting time at high state of charge, parking in cooler areas and out of the sun, limiting time at high battery temps.

If you had started following Leaf back at the beginning and lived in a hotter climate, perhaps your tune would be different.

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+1

There is a HUGE difference in battery health from one to another car INCLUDING cars in the same region. It should be obvious by now that its US causing the good and the bad. Now we can waste our time blaming Nissan or we can simply realize this what we got so now what? Realize we may not be happy with the LEAF but for most of us, that is all we got and we have to learn to live with it.

We do have options and some are easy, some are not but knowing what matters is the key. Then it becomes up to us to determine how much effort we want to put into getting more effective use from our LEAFs.

LeftieBiker said:

The problem I see with this approach is that it doesn't correct for headwinds or tailwinds, or for that matter, air density at different temps.

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None of that should matter. I could go up hills all the way for the test. The forces acting on the car, and the distance driven are corrected for in the test -- at least at distances long enough to impart accuracy to the consumption and SoC meters.

Driving up (or down) a hill doesn't negate the extra force applied by the wind on the car. The two are separate components of the equation.

LeftieBiker said:

Driving up (or down) a hill doesn't negate the extra force applied by the wind on the car. The two are separate components of the equation.

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You are not getting it. If a hill does not affect the result, why would wind ? LOL
Apply any wind (less than a hurricane) you care to, it DOES NOT MATTER to this test.

SageBrush said:

LeftieBiker said:

Driving up (or down) a hill doesn't negate the extra force applied by the wind on the car. The two are separate components of the equation.

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You are not getting it. If a hill does not affect the result, why would wind ? LOL
Apply any wind (less than a hurricane) you care to, it DOES NOT MATTER to this test.

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I don't get it either then...

When the wind blows it can drop Leaf range by a significant amount. If you get tailwind both ways or a headwind both ways of equal speed and direction, then it doesn't matter.

I basically do this all the time. Sometimes 40+ miles, usually 20-25mi one way. My car always lives at 100%. I don't care enough to charge limit or time it. I plug it in when I park and it charges to 100% until I am ready to drive it again. At the beginning of every 100%-SOC drive I reset the trip meter.

I have had many days where my 25 mile drive has used 75% or 80% of the battery due to winds versus the 40% it usually takes. And on the way back it is usually 25% to 30% but I have also seen it in the 80% used.

Wind makes a huge difference as does speed.

I guess Sagebrusque has undergone a metamorphosis and...become a god. This is two people in one day telling me I don't understand the laws of physics as they do. Maybe I should start trying to find out if I've crossed over to another universe, with somewhat different laws.

EDIT: what he is doing is trying to measure percent charge drop per mile driven, corrected for relative efficiency. In theory this would give the pack's capacity at that time, but I doubt very much that the instrumentation upon which he is relying is accurate enough to give a good result.

2k1Toaster said:

I don't get it either then...

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I'm calculating kWh per full battery charge.
It does not matter if the kWh are used up in 30 miles or 100 miles.

Say my full battery capacity is B in kWh
And my test consumption rate is C in kWh/mile
And distance traveled during the test is D in miles

Then
C * B = D

I read the C and D meters, and calculate battery capacity

In the beginning, we there were 12 bars on the dashboard. Then came Leafspy, which was an amazing product...

Now we are calculating different formulas with ambient temperature, relative humidity, and angle of attack of the car in relation to the earth's core.... Each person can do what they want, but what difference is it to know your battery is 90% STATE OF HEALTH... or 91.39%??

There are many other calculations one can make, like balancing our checkbooks and measuring how much money we waste at Starbucks and Dunkin on mococho-lates.....

I tried out the method today, but decided to use only a way-one trip that is an elevation climb in order to use up most of my battery on one charge.

Per LEAF meters:
Start SoC: 99%
End SoC: 19%

Trip: 47 miles
15-25F
3-4 Temp bars on battery meter

Consumption Rate: 3.2 miles/kWh

47 miles / 3.2 miles/kWh = 14.68 kWh consumed over 80% SoC use,
So 14.68/0.8 = 18.36 kWh battery capacity

The other direction was (IIRC) 46 miles using 52% SoC at a rate of 4.8 kWh/mile. That works out to 18.43 kWh battery capacity.
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LEAFspy reported 57.57 Ahr capacity when I measured at 50% SoC earlier in the month. This works out to 20.7 kWh by LSpy using 360 v average over the discharge cycle.

I am not sure how to resolve the LSpy Vs metered travel discrepancy. Does the SoC reading have a built-in lower buffer that is unreported at the lower end ? Or perhaps this is just a battery temperature effect. One thing for sure though, this method can resolve uncertainly whether a battery reset has recently occurred

We have no reason to think that Nissan was careful to provide an accurate SOC reading, as opposed to one that offered a little more protection against running the car out of charge.

LeftieBiker said:

We have no reason to think that Nissan was careful to provide an accurate SOC reading, as opposed to one that offered a little more protection against running the car out of charge.

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Easy enough to check:

Go out for a test drive and note results at say 50,40,30,20, and (10 and Turtle, close to home.) Should take less than an hour with cabin heating and higher posted speed limits.

Anyway, I think a better question is whether the SoC and consumption meters are relying on the same underlying measure in part. That could negate a systemic bias.

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Meter accuracy is a fair discussion. Wind effect is not. Have you gotten up to speed on that point of New Age Physics and beginners algebra yet, Leftie ?

I'm tired of your shitty attitude, and while you do occasionally contribute something worthwhile, it isn't worth having to deal with your personality. Had you just explained your reasoning up front, there would have been no misunderstanding. Anyway, welcome to my user filter.

LeftieBiker said:

Anyway, welcome to my user filter.

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Thank you.