Discuss data from the LEAF Battery app, and Comparisons

[klapauzius]

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.

 

[surfingslovak]

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 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]

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.

 

[GregH]

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.

 

[JPWhite]

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.

 

[DaveEV]

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?

 

[JPWhite]

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.

 

[DaveEV]

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]

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.

 

[opencar]

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?

 

[klapauzius]

I did read the AH values at various temperatures, when that car had sat for a while and I seem to get the same value everytime, over the course of a week now. I noticed that the 12 V voltage though varies wildly on single readings. Is that because the car is running? I cant get any data from my BT adapter, when the car is turned off.

Also, I noticed that the Wh counter goes up, regardless of load. I sat in the car, with no significant power input/output and it went up at a rate of 3-4 kW.

 

[DaveEV]

The 12V battery will typically read one of these values for me:

1. 13.0V - Car has been on a while, the 12V battery is being float charged.
2. mid-low 12V - Car is not fully on, DC-DC inverter is not on.
3. mid-high 13V - Car was just turned on, 12V battery is being charged.

 

[LEAFfan]

I noticed my AH and CAP readings decreasing as the ambient temps keep rising. We may hit 110F today (108 yesterday). Normal/Ave. is 100F.

 

[DaveEV]

Hit LBW today and watch watching the SOC on the app - right around 26% - quite high. Last time it was around 24%.

Interestingly, have the app's DTE zero'd at 4 kWh remaining / 4.0 mi/kWh and still had about 4 miles / 1 kWh to go.

Ah reading on my car is around 58.2.

 

[opencar]

Hit LBW today and watch watching the SOC on the app - right around 26% - quite high. Last time it was around 24%.

Interestingly, have the app's DTE zero'd at 4 kWh remaining / 4.0 mi/kWh and still had about 4 miles / 1 kWh to go.

Ah reading on my car is around 58.2.

drees - do you notice appreciable decrease in your Ah over the last month of logging? i've noted the steady decrease every since i started monitoring & I note we are in the same area. i'm at 57.4 currently & have dropped 2% over the last month.

 

[DaveEV]

May 1st it was 59.40, this morning 58.19, just about exactly 2%!

 

[JPWhite]

May 1st it was 59.40, yesterday 58.2, just about exactly 2%!

We seem to have similar aged LEAF's

In the last 15 days my Ah reading has dropped from 60.5 to 57.8 or about 4.5%.

I believe we are seeing evidence of Jack Ricards 'live by the turtle, die by the turtle' speech he gave regarding the Arizona range tests performed last year. He blames the BMS and says the battery is just fine. I don't agree it's just the BMS, but he has a point that the BMS is misbehaving in warm/hot climates during the summer.

I'm hopeful that Nissan will give us a BMS firmware update when they finally get round to issuing the retroactive capacity warranty. With any luck will will get part of this 'lost capacity' back.

 

[klapauzius]

The temperature effect must kick in somewhere higher than 25 C. This is what I measured today and AH cap is unchanged from earlier recordings at 18 C.

 

[Stoaty]

The temperature effect must kick in somewhere higher than 25 C. This is what I measured today and AH cap is unchanged from earlier recordings at 18 C.

I have had some loss of capacity (about 0.7% less on the Leaf Battery App) in the last month. Battery has spent some time between 76 and 86 degrees F. recently. For the prior 6 months, capacity appeared to be solid as a rock (but no Battery App then).

 

[JeremyW]

Went from 61.7 to 60.5 over May. Most of the loss happened after quick charging.

In fact, I have noted loss after EVERY quick charge, but do get a "bounce back" after a day or so. If it's one partial quick charge I usually get back to roughly the same Ah value. If it's multiple QC's in a day, the bounce back is substantially less (for a net loss).

Also to note, I'm at about 13,500 mi or so. Looks like I'm down just as much as the '11s in so cal. I believe this is due to my excessive use of quick charging (or more likely the heat caused by it).