klapauzius
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Re: Discuss data obtained from the LEAF Battery app

Thu May 30, 2013 12:33 pm

GregH wrote: Without calibration the difference of 1A over the course of a 5 hour charge at 8-9A can be rather large. We haven't found anything akin to a running Ah counter in the data so far.
How the car calculates the Ah capacity (or Gids for that matter) is not entirely understood... but it seems to be a mixture of Ah counting and voltage and temperature analysis..
[edit] Actually I should amend that.. Doing a bunch of partial charges on the new car (say from 30% to 70% up and down) does introduce a drift in the SOC such that at lower voltages sometimes the car snaps down to the lower Gid/SOC over the course of a few minutes when it realizes it's off. I've seen this a few times and it's somewhat alarming. Now I pay more attention to voltage than Gids when I'm under LBW.
If it is a 1 A bias that would make a difference, yes. Can this be measured over the course of an hour? I assume the Amps-in value is on the CAN bus, so it could be recorded? If so, one could do an integration and match with the reported value?
I think the poor sensor quality is no real hindrance to coulomb counting, if it does not introduce bias.

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surfingslovak
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Re: Discuss data obtained from the LEAF Battery app

Thu May 30, 2013 12:55 pm

Stoaty wrote:
GregH wrote:I actually notice slight cooling during the morning commute which tells me cooling the underside of the car is more important than cooling the passenger compartment. Kinda flies in the face of thermodynamics, but that's what I've seen so far.
Image
Makes me wonder if putting a small fan under the car at night to circulate air better would improve night time cooling during the summer months when I need it most. The air in my underground parking garage doesn't move much.
I always thought that there was significant airflow around the battery case during operation of the vehicle, and your recent observation would seem to corroborate that.

GregH
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Re: Discuss data obtained from the LEAF Battery app

Thu May 30, 2013 1:47 pm

Stoaty wrote:
GregH wrote:I actually notice slight cooling during the morning commute which tells me cooling the underside of the car is more important than cooling the passenger compartment. Kinda flies in the face of thermodynamics, but that's what I've seen so far.
Makes me wonder if putting a small fan under the car at night to circulate air better would improve night time cooling during the summer months when I need it most. The air in my underground parking garage doesn't move much.
I do. I put a cheap little fan blowing air under the car and crack the garage door about 4 inches.
'17 blue Volt Premier w/ACC
'12 SL black Leaf
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GregH
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Re: Discuss data obtained from the LEAF Battery app

Thu May 30, 2013 1:52 pm

klapauzius wrote:
GregH wrote: Without calibration the difference of 1A over the course of a 5 hour charge at 8-9A can be rather large. We haven't found anything akin to a running Ah counter in the data so far.
How the car calculates the Ah capacity (or Gids for that matter) is not entirely understood... but it seems to be a mixture of Ah counting and voltage and temperature analysis..
[edit] Actually I should amend that.. Doing a bunch of partial charges on the new car (say from 30% to 70% up and down) does introduce a drift in the SOC such that at lower voltages sometimes the car snaps down to the lower Gid/SOC over the course of a few minutes when it realizes it's off. I've seen this a few times and it's somewhat alarming. Now I pay more attention to voltage than Gids when I'm under LBW.
If it is a 1 A bias that would make a difference, yes. Can this be measured over the course of an hour? I assume the Amps-in value is on the CAN bus, so it could be recorded? If so, one could do an integration and match with the reported value?
I think the poor sensor quality is no real hindrance to coulomb counting, if it does not introduce bias.
Early versions of the Dash Display (with the 8 line screen.. GizmoV1 as Gary called it) had a resettable Ah counter. Frankly after seeing the big difference between the two cars I just gave up. Yeah I could have had it self calibrating (we did this at EnergyCS and EDrive) but with all the other info from the car, adding more on my side didn't really seem to be worth while.
'17 blue Volt Premier w/ACC
'12 SL black Leaf
'11 SL blue Leaf
RAV4-EV 2002-2005
Gen1 & Gen2 EV1 1997-2003
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JPWhite
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Re: Discuss data obtained from the LEAF Battery app

Fri May 31, 2013 5:50 pm

drees wrote:It's obvious that the Ah reading like GIDs are affected by battery pack temperature - but that doesn't necessarily correlate to an actual change in capacity.

So you should only be comparing those readings under similar temperature conditions.
I would tend to agree with you. In the last 15 days my Ah reading has dropped 4.4%. I doubt my battery is falling apart, probably the buggy s/w in the LEAF over-protecting the battery.

Get LBW most days now as I arrive home thanks to the 'reduced capacity'. SOC shows 22.5% at LBW and 59 'estimated GID's' so I'm not worried about it.

That first bar may go out this summer if the Ah reading keeps going down. I'm within 1-2% now.
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DaveEV
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Re: Discuss data obtained from the LEAF Battery app

Fri May 31, 2013 10:52 pm

JPWhite wrote:I would tend to agree with you. In the last 15 days my Ah reading has dropped 4.4%. I doubt my battery is falling apart, probably the buggy s/w in the LEAF over-protecting the battery.

Get LBW most days now as I arrive home thanks to the 'reduced capacity'. SOC shows 22.5% at LBW and 59 'estimated GID's' so I'm not worried about it.
The real request is - where is that capacity going? If anything, short-term warming of the pack should increase usable capacity, not the opposite, yet the Ah reading and GIDs seems to respond pretty quickly to an increase in temperature. Is the pack voltage at LBW getting higher? Pack voltage at 80, 100% charge seems to remain constant. Or perhaps the pack voltage readings through the CAN bus is not accurate and they are being fudged?

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JPWhite
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Re: Discuss data obtained from the LEAF Battery app

Sat Jun 01, 2013 5:12 am

drees wrote:
JPWhite wrote:I would tend to agree with you. In the last 15 days my Ah reading has dropped 4.4%. I doubt my battery is falling apart, probably the buggy s/w in the LEAF over-protecting the battery.

Get LBW most days now as I arrive home thanks to the 'reduced capacity'. SOC shows 22.5% at LBW and 59 'estimated GID's' so I'm not worried about it.
The real request is - where is that capacity going? If anything, short-term warming of the pack should increase usable capacity, not the opposite, yet the Ah reading and GIDs seems to respond pretty quickly to an increase in temperature. Is the pack voltage at LBW getting higher? Pack voltage at 80, 100% charge seems to remain constant. Or perhaps the pack voltage readings through the CAN bus is not accurate and they are being fudged?
I agree the capacity should be going up, but I believe the BMS is being over conservative and is putting more and more capacity into 'reserve' as pack temperature rises and hiding it from the drivers instrumentation. My pack has been pretty consistently in the mid to high 80's throughout this 15 day period at the end of my commute home. I believe this is a symptom of the 'instrumentation error' Nissan alluded to in the Phoenix degradation debacle. Some real degradation did occur in Pheonix, but 'instrumentation error' just exacerbated the issue by reducing driveable range further. If they ever issue the retroactive battery capacity warranty along with a firmware fix, It'll be interesting to see if any 'lost' capacity magically returns.

To answer one of your questions, in a random sample of one, hardly significant, I see an increase of pack voltage by 3 volts (a little less than 1%) for the same 26.5% SOC% reported across the CAN bus over the same 15 day period. This is indication that some capacity is being hidden at the same SOC.
--
JP White
http://jpwhitenissanleaf.com
2011 Blue SL-e, 132,400 Miles.
Lost 5 Capacity bars
7/18/13 (29,206), 8/25/14 (51,728), 7/12/15 (71.108), 5/12/16 (88,362), 10/17/16 (96,532)
New Battery 12/3/16 (98,956)
2018 Model 3 20,000 Miles.

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DaveEV
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Re: Discuss data obtained from the LEAF Battery app

Sat Jun 01, 2013 3:40 pm

JPWhite wrote:To answer one of your questions, in a random sample of one, hardly significant, I see an increase of pack voltage by 3 volts (a little less than 1%) for the same 26.5% SOC% reported across the CAN bus over the same 15 day period. This is indication that some capacity is being hidden at the same SOC.
Very interesting. Would be nice to try to collect battery pack voltage at various low SOC% levels to try to draw some conclusions here.

jclemens
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Re: Discuss data obtained from the LEAF Battery app

Sat Jun 01, 2013 4:26 pm

I have been doing some logging of the voltage, but doing it right takes a while. There is no value in measuring the voltage after driving or charging. The only accurate way to know true state of charge is on cells that have had a few hours to rest with no load and no charging. The longer the better. This can be done when the car is in acc mode.

I recently did an experiment, i left the car with low battery warning uncharged overnight, recorded the data befor and after charging. when i turned it on to check after charge was complete, it was at 80% as expected. But after i disconnected the 12v battery to clean the terminals (blue fuzz), i turned the car back on and it was only at 75%. I plugged it in and it took 1kwh... Very odd.
I will post my data when i have more info... Might take a couple months.
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opencar
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Re: Discuss data obtained from the LEAF Battery app

Sun Jun 02, 2013 9:10 am

trying to determine what factors affect the fluctuations of the Ahr parameter reported by the app. Logging over the last couple weeks didn't provide any obvious correlation to traction battery temps. i did notice a correlation of changes in Ahr coinciding w/ sudden high voltage readings of the 12V battery. anybody have any insight into this issue?
1st bar- 22K, 27mo, Ah=55.29
2nd- 33K, 37mo, Ah=51.54
3rd- 41K, 46mo, Ah=47.47
4th- 49K, 53mo, Ah=43.28
Warranty Lizard- 50K, Oct'15
1st bar- 34K, 44mo, Ah=55.25, 84K cum mi

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