edatoakrun
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 8:08 am

RegGuheert wrote:
drees wrote:
TonyWilliams wrote:turtle voltages had a SIXTY volt spread. I'll suggest that batteries at 350 volts could have gone much farther, maybe as far as my car went with 290 volts remaining. This reeks of a BMS problem; hardware of software, or both.
There's only two things that might cause one car to turtle at 350V and another to turtle at 290V.

1. A software problem. No further explanation needed here.
2. At least one cell-pair with significantly lower capacity than the rest - one cell-pair hit the low-voltage limit and the BMS shut the party down. Should be easy to check with a Consult by taking this car down near turtle.
Agreed, except I think a software problem is a very long shot here. I would expect software problems to arise in more than a couple cars and in more than just one climate.

The BMS in the LEAF terminates both charging and discharging based on voltages at the cell and the pack level. Phil has told us that his LEAF's voltmeters appear to be accurate to within about 0.1% and that the low-voltage meters cross-check with the high-voltage meters and throw codes if there is a discrepancy. So, no, I do not think we are losing any range due to instrumentation issues.

The sixty-volt difference in discharge voltage is *precisely* what I would expect to see between a new pack and a severely degraded pack. The cells in the new pack should all have similar capacities, so none should go below the knee prematurely. But in a pack without a TMS driven in a very hot climate some cells will live in an even HOTTER environment than others. Those cells will deteriorate faster and will therefore have higher internal electrical resistance, possible greatly higher. As a result those cells will get even hotter and will quickly go downhill.

This condition is exactly what Nissan's CELL VOLTAGE LOSS INSPECTION test is designed to identify. If Scott's car is the one that terminated at 350V, then I find it irresponsible that Nissan has not reported the amount of variation found in the cells in his pack.

Again, I will say that I would find a histogram of cell capacities from a degraded LEAF to be quite informative right about now. I don't think we can expect to get that from Nissan. Anyone want to purchase a battery and give the old one to Phil to document?
Can you rule out the possibility of adaptive battery management by the BMS?

IMO, Nissan must have designed the LEAF BMS with battery life, rather than convenience to owners, as the primary goal.

How successful Nissan was, is now the larger question.

But can you conclusively rule out variable battery warning levels, and shut down, as evidence of a the BMS functioning as designed, rather than a malfunction?

Would it not make a lot of sense for Nissan to include measures intended to protect of the battery from premature capacity loss (or, much worse from Nissan's point of view, a "failure" warranty claim) based on the prior conditions of use, into the BMS?

As one example, the BMS may have noticed a Nissan driver believes they can make daily 60 mile freeway commute in Phoenix temperatures on one charge, (or a 80 mile one, with a quickie at the local DC) in their LEAF and now, the BMS is trying to tell the Driver, that he or she cannot, and still expect to maintain (some unknown level of) capacity for (some unknown) period of time.
Last edited by edatoakrun on Thu Sep 20, 2012 8:26 am, edited 1 time in total.
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Stoaty
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 8:18 am

edatoakrun wrote:
Stoaty
Ed, we already know your opinion. Please give it a rest.
No, I don't think I will.
OK, added to ignore list. I hope you aren't channeling Orientexpress.
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TonyWilliams
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 8:45 am

edatoakrun wrote:
Stoaty
Ed, we already know your opinion. Please give it a rest.
No, I don't think I will.

I wrote that summary above because of the deficiencies of Tony’s own effort.
Ed, YOU'RE A WINNER !!!!!

My test is bad. Now, you can rest easy tonight. Night, night.

:roll:

PS: OrientExpress might want to snuggle tonight, so you two should get together for a Tony bashing.
Last edited by TonyWilliams on Thu Sep 20, 2012 9:03 am, edited 1 time in total.

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DaveEV
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 8:53 am

KJD wrote:
drees wrote:Interesting though when faced with a battery that is 70%, 80% or 90% capacity knowing that at best, LBW occurs with about 4 kWh remaining in the pack and for the sake of the argument, range when new is 80 miles.

We all know that the average user doesn't like to go below LBW - which means leaving 4 kWh (out of 22.5 kWh assuming 281GID and 1GID=80Wh) on the table. We'll call 100% - LBW "usable".
OK correct me if I am wrong here but I seem to remember reading somewhere else that 21 kWh was what was usable not 22.5
22.5 kWh assumes 1 GID = 80 Wh and 281 GID = max charge.

Realistically, even a new car will not always hit 281 GIDs on a full charge - ~276 appears to be common, for example - perhaps if your battery isn't perfectly balanced. And turtle comes on around 7 GIDs, so 276-7 = 21.5 kWh usable. Pretty close to 21.5 kWh "usable".

That post is really just showing how a fixed LBW set point makes capacity loss look worse than it is for most people since most people only look at range from 80-100% to LBW as "usable". The actual numbers don't matter all that much.

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TonyWilliams
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 9:00 am

KJD wrote:
drees wrote:Interesting though when faced with a battery that is 70%, 80% or 90% capacity knowing that at best, LBW occurs with about 4 kWh remaining in the pack and for the sake of the argument, range when new is 80 miles.

We all know that the average user doesn't like to go below LBW - which means leaving 4 kWh (out of 22.5 kWh assuming 281GID and 1GID=80Wh) on the table. We'll call 100% - LBW "usable".
OK correct me if I am wrong here but I seem to remember reading somewhere else that 21 kWh was what was usable not 22.5
22.5 is the official stored capacity, as shown above (281*80). But, there are losses to extract that stored power, and my rule of thumb is 75*281 of extracted power, AS MEASURED BY THE DASH INSTRUMENTS. That means that if you drive 4 miles/kWh as the dash displays, the car will go 84 miles (84/4=21), so I call that "useable energy", as opposed to 22.5 "stored energy". Edit: yes, like drees said, we leave a tiny bit of power at the bottom, between turtle and the point that the battery shuts down.

The car absolutely will NOT go 22.5*4 = 90 miles. This comes up a lot. The battery's rated capacity is 24kWh, but it is never charged above 95% SOC, and never allowed to discharge below 2% SOC of the rated capacity of the battery. 22.5/24=93.75% of the rated battery capacity is stored for use.

You'll note that I used 4 miles/kWh for all the examples, and that was exactly the target economy we intended to have at 100kmh speed.

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RegGuheert
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 9:07 am

edatoakrun wrote:Can you rule out the possibility of adaptive battery management by the BMS?
No, I cannot rule out anything since we have very limited data. I am reading the tea leaves like everyone else and making educated guesses about what I believe is going on.
edatoakrun wrote:Would it not make a lot of sense for Nissan to include measures intended to protect of the battery from premature capacity loss (or, much worse from Nissan's point of view, a "failure" warranty claim) based on the prior conditions of use, into the BMS?
Perhaps, but doing it by ONLY raising the voltage at which you go into turtle makes NO sense to me. If Nissan wants to protect the car from us, they should trim the top end AND the bottom end and keep us closer to the middle of the SOC band.

Again, the signature here looks just like a failing cell or cells which have gone below the cutoff voltage way before the rest of the pack. Until that obvious conclusion is ruled out I don't see a need for speculating that the BMS is starting to analyze the desires of the driver in its algorithms.
RegGuheert
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DaveinOlyWA
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 9:17 am

TonyWilliams wrote:
KJD wrote:
drees wrote:Interesting though when faced with a battery that is 70%, 80% or 90% capacity knowing that at best, LBW occurs with about 4 kWh remaining in the pack and for the sake of the argument, range when new is 80 miles.

We all know that the average user doesn't like to go below LBW - which means leaving 4 kWh (out of 22.5 kWh assuming 281GID and 1GID=80Wh) on the table. We'll call 100% - LBW "usable".
OK correct me if I am wrong here but I seem to remember reading somewhere else that 21 kWh was what was usable not 22.5
22.5 is the official stored capacity, as shown above (281*80). But, there are losses to extract that stored power, and my rule of thumb is 75*281 of extracted power, AS MEASURED BY THE DASH INSTRUMENTS. That means that if you drive 4 miles/kWh as the dash displays, the car will go 84 miles (84/4=21), so I call that "useable energy", as opposed to 22.5 "stored energy". Edit: yes, like drees said, we leave a tiny bit of power at the bottom, between turtle and the point that the battery shuts down.

The car absolutely will NOT go 22.5*4 = 90 miles. This comes up a lot. The battery's rated capacity is 24kWh, but it is never charged above 95% SOC, and never allowed to discharge below 2% SOC of the rated capacity of the battery. 22.5/24=93.75% of the rated battery capacity is stored for use.

You'll note that I used 4 miles/kWh for all the examples, and that was exactly the target economy we intended to have at 100kmh speed.
TOTALLY a different page here; but in relaying personal experience using questionable means.

i mention this only because of exact same results two days in a row.
checked LEAF this morning after full charge. performance last night 4.2 m/k. GOM 88 and SOC 271 GID.

this does equate to the 4m/k and 84 miles.

in the interest of full disclosure. drove 62.9 miles and used 18 Kw (rounded) to recharge.
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Volusiano
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 9:23 am

surfingslovak wrote:But back to Volusiano's question. What other instrument or control is out of whack or behaving inconsistently? I could think of the obvious one: battery capacity bars. If I recall correctly, they were not showing the correct remaining capacity in a number of cars. Several of us have the 2011 shop manual and could make the relevant section available.
Yes, the Tempe AZ test results established that the capacity meter instrument is not accurate. But I can't simply take those results to a dealership and tell them to fix my own capacity meter because they will say that those are other cars' results and not mine.

OK, I can do a test on my own car to get my own result, but it doesn't mean that the dealership will have to agree with any test result I claim to have obtained myself, unless they agree to do the test again themselves to independently verify their own result. And don't forget that the test is meaningless without having a valid control car's result for use as reference.

So more likely than not, they will just brush it off and say "Are you kidding us? We don't have the time and inclination to do all those testings. Even if we agree to do the test, it'll cost a lot of time and money and Nissan will not sanction and pay us for such a test."

Or they can also say "We checked with Nissan and they told us that the capacity bar instrument is only for rough estimation and is not guaranteed to be 100% accurate. Nissan told us they will revise the documentation to reflect this".

The way I see it, unless instrument accuracy is required because it has a direct effect on the safe operation of the car, Nissan and the dealerships can easily squirm their way out of guaranteeing instrument accuracy.

For example, if you reach turtle all of a sudden without seeing LBW and VLBW first, then that's an obvious safety issue that Nissan has to concede and address. Or if the speedometer is insanely wrong, causing you to drive much faster than the speed limit, which constitute a safety hazard. Or if the odometer is insanely wrong, causing you to underestimate your trip, resulting in not being able to complete it before the battery juice runs out. But almost anything else probably does not require Nissan to guarantee instrument accuracy. They can simply say that they don't have to guarantee the accuracy of anything else that is not a safety related issue.

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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 9:31 am

DaveinOlyWA wrote: checked LEAF this morning after full charge. performance last night 4.2 m/k. GOM 88 and SOC 271 GID.

this does equate to the 4m/k and 84 miles.
Guys, we don't need to continue beating a dead horse. Nissan says it will go 84 miles at 4miles/kWh in their own published data, and I know it will, also, after having done it about a gazillion times. Obviously, climate control is a variable that we didn't use (and how a spread of 76-84 miles makes sense). It will only go 76 miles (or actually less with significant heater use) with climate control on. Simple.

With no climate control, 4 miles/kWh, every new LEAF that shows 281 Gid will bang out 84 miles with the control parameters met (level, no significant wind, 70F, etc).

Let's please stop hammering this. If Nissan is dumb enough to spew out an "Ed" or "OE" styled soliloquy, we have more ammo.

Ok, so truce?

edatoakrun
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Re: Phoenix Range Test Results, September 15, 2012

Thu Sep 20, 2012 9:44 am

RegGuheert wrote:
edatoakrun wrote:Can you rule out the possibility of adaptive battery management by the BMS?
No, I cannot rule out anything since we have very limited data. I am reading the tea leaves like everyone else and making educated guesses about what I believe is going on.
edatoakrun wrote:Would it not make a lot of sense for Nissan to include measures intended to protect of the battery from premature capacity loss (or, much worse from Nissan's point of view, a "failure" warranty claim) based on the prior conditions of use, into the BMS?
Perhaps, but doing it by ONLY raising the voltage at which you go into turtle makes NO sense to me. If Nissan wants to protect the car from us, they should trim the top end AND the bottom end and keep us closer to the middle of the SOC band.

Again, the signature here looks just like a failing cell or cells which have gone below the cutoff voltage way before the rest of the pack. Until that obvious conclusion is ruled out I don't see a need for speculating that the BMS is starting to analyze the desires of the driver in its algorithms.
Where are the voltage levels at "100%", and at warning levels and stop for all the test LEAFs posted?
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