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post #11 of 27 (permalink) Old 07-10-2016, 09:43 AM
 
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Working ED Battery Checker in Toronto

@odyssey I finally got around to soldering the pins on the CANBus board and flashing the arduino. Piece of cake. Thanks for all your hard work!

One thing that I did find interesting is that the last service reported 50.2 Ah. About 1 Ah lower than any of the calculated min/max/mean CAP values.

From the individual cell values I verified the summary CAP values using a spreadsheet. The numbers match those reported from the arduino firmware.

Any thoughts?

For reference here's some of the data from the first reading:


-----------------------------------------
Time [hh:mm]: 11:05, ODO : 23229 km
-----------------------------------------
Battery-Production [Y/M/D]: 2013/9/28
Rev.[Y/WK/PL] HW:2013/29/0, SW:2013/29/1
Initial Capacity : 53.1 Ah, Loss: 0.005 %
-----------------------------------------
SOC : 86.5 %, realSOC: 84.8 %
HV : 374.3 V, -1.03 A, -0.44 kW
LV : 14.0 V
-----------------------------------------
Temperatures Battery-Unit /degC:
module 1: 25.6, 26.5, 25.7
module 2: 25.8, 26.4, 25.8
module 3: 25.6, 26.3, 25.4
mean : 25.9, min : 25.4, max : 26.5
coolant : 24.5
-----------------------------------------

-----------------------------------------
Individual Cell Statistics:
-----------------------------------------
CV mean : 4005 mV, dV = 29 mV, s = 7.58 mV
CV min : 3991 mV, # 49
CV max : 4020 mV, # 11
-----------------------------------------
CAP mean: 18806 As/10, 52.2 Ah
CAP min : 18477 As/10, 51.3 Ah, # 72
CAP max : 19053 As/10, 52.9 Ah, # 9
-----------------------------------------
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post #12 of 27 (permalink) Old 07-10-2016, 12:53 PM
 
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Congrats! Now we have two in north America!

Quote:
Originally Posted by Blaine View Post
the last service reported 50.2 Ah. About 1 Ah lower than any of the calculated min/max/mean CAP values.
Reproducibility is about +/- 1Ah, so that difference is not surprising. There also seems to be a temperature coefficient (even though the reported numbers are temperature compensated - just not quite enough). I get on average 1.5Ah more now than I did last winter.

The smallest individual cell capacity is what would show up in the MB battery test report. 51.3Ah in your case.
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post #13 of 27 (permalink) Old 07-10-2016, 02:05 PM
 
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Good info - thanks. Just had my battery service last week and it came in at 50.8 Ah.

Len
2014 EV
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post #14 of 27 (permalink) Old 07-11-2016, 10:55 AM Thread Starter
 
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Thumbs up

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Originally Posted by Blaine View Post
@odyssey I finally got around to soldering the pins on the CANBus board and flashing the arduino. Piece of cake. Thanks for all your hard work!
Great news! (Y) and THX for the compliment ;-) SuperSmartie also worked hard on validating the readouts - so a great THX to him, too!!!

Some of the data is still experimental like the initial capacity and the loss. In an upcoming release I will make a "experimental"-section to clarify the untested values.

As SuperSmartie said: the minimum capacity in the individual section counts. All cells are connected in series and the lowest value limits the usable capacity.

In the github-repo I made a Wiki and hopefully will add some explanations in the future.

Congrats to the 51.3 Ah - I think is a good value for the pack @ ~23000 km ;-)

Best regards
odyssey
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post #15 of 27 (permalink) Old 07-16-2016, 06:36 AM
 
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Battery temperatures after a highway run

For those who might be curious, here are some battery temperatures after a run on the highway. Total trip time was about 55 minutes with half the distance slow and the other half at about 120 km/h. Distance was approximately 40 km. Outside temperature was roughly 28 C and the car had been sitting outside during the day. AC was not in use inside the car.

Battery started out fully charged.


-----------------------------------------
Time [hh:mm]: 18:14, ODO : 23557 km
-----------------------------------------
SOC : 73.0 %, realSOC: 74.5 %
HV : 364.3 V, 8.72 A, 3.19 kW
LV : 13.8 V
-----------------------------------------
CV mean : 3892 mV, dV = 21 mV
CV min : 3882 mV
CV max : 3903 mV
OCVtimer: 1128 s
-----------------------------------------
Temperatures Battery-Unit /degC:
module 1: 31.7, 34.4, 32.3
module 2: 32.0, 34.2, 32.2
module 3: 31.5, 34.4, 33.2
mean : 32.9, min : 31.5, max : 34.4
coolant : 29.3

-----------------------------------------
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post #16 of 27 (permalink) Old 07-18-2016, 01:43 PM
 
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So with the published spec of 17.6kWh, that's 3.7V for the 93 cells with a peak capacity of 51.1Ah. Charging the batteries up to 4.2V with a "real" initial capacity of 53.1kWh pushes the maximum to 20 kWh. I'm guessing the "real" SOC versus advertised SOC is to absorb some buffer? Is there some hidden potential here we can unlock?

PS - I'm planning on making one of these as well, so there'll be one in Cow-Town soon.
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post #17 of 27 (permalink) Old 07-18-2016, 02:59 PM
 
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I think the effective max capacity of the lowest cell in each of the three modules will limit the usable top end charge, and limit squeezing out extra from the pack.

When (if?) i get some time from work I want to setup the logger behaviour and see what happens while the car is in use.

It will be good to have multiple data points though. Let us know if there is anything we can do to help with your build.
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post #18 of 27 (permalink) Old 07-18-2016, 03:14 PM
 
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Quote:
Originally Posted by nonarkitten View Post
17.6kWh, 20 kWh
Battery capacity is always measured in Ah. The kWh energy capacity is very dependent on discharge conditions, so it's always just a "nominal" value, assuming some "nominal" voltage, typically 3.7V for LiIon. Don't pay too much attention to the kWh figures, focus on the Ah ones.


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I'm guessing the "real" SOC versus advertised SOC is to absorb some buffer? Is there some hidden potential here we can unlock?
Only in so far that the two diverge at the low end: When the dashboard guessgauge shows zero, the BMS typically still shows >10% left, which is really there and can be used (I tested that). So you can still get home if the dashboard gauge hits zero and you have a few miles left to go.
Problem is, without the odyssey box you can't depend on it. The difference is not always 10%, it can be anywhere between zero and 20%.

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PS - I'm planning on making one of these as well, so there'll be one in Cow-Town soon.
Excellent! The more heads, the more ideas!
How about building a local display that shows realSOC, so you really can use the hidden potential?
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post #19 of 27 (permalink) Old 07-19-2016, 01:48 PM
 
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Quote:
Originally Posted by SuperSmartie View Post
Battery capacity is always measured in Ah. The kWh energy capacity is very dependent on discharge conditions, so it's always just a "nominal" value, assuming some "nominal" voltage, typically 3.7V for LiIon. Don't pay too much attention to the kWh figures, focus on the Ah ones.
Ah, gotcha (see what I did there?).

Quote:
Originally Posted by SuperSmartie View Post
Only in so far that the two diverge at the low end: When the dashboard guessgauge shows zero, the BMS typically still shows >10% left, which is really there and can be used (I tested that). So you can still get home if the dashboard gauge hits zero and you have a few miles left to go.
Problem is, without the odyssey box you can't depend on it. The difference is not always 10%, it can be anywhere between zero and 20%.

Excellent! The more heads, the more ideas!
How about building a local display that shows realSOC, so you really can use the hidden potential?
That's a great idea -- a smart ED "scangauge".
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post #20 of 27 (permalink) Old 09-04-2016, 05:18 PM
 
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Originally Posted by odyssey View Post
The first step is to verify if your OBD-reader is CAN-Bus capable. The data requests are not standard OBD (PID) queries. If your software is flexible enough you can send CAN-Bus messages and get the multi-frame reply. Look at my code - you will find predefs for the the requests... Then you have to parse the packet and have to know the data-position and calculate your own values - have fun!
In theory, I can use a bluetooth CANBUS Capable OBDII Reader and build up android app to do the same thing, as long as I take your queries and parse the response?
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