Oleksiy
Posts: 93
Joined: Fri Mar 23, 2018 4:30 am
Location: Kyiv, Ukraine

Some stats for the year of use

Mon Jun 10, 2019 2:14 pm

Here's the screenshot of the pivot table with monthly averages from my daily stats file I've logged for more than a year of use. My i3 is 09/2015 60Ah BEV, 30.5K miles now, I bought it at 15.7K miles in the US and brought it to Ukraine in the end of May 2018. The A column contains months - May-Dec 2018 and Jan-June 2019. Somehow I can't display these in En in the pivot. Other column names should be self-explanatory, but let me know if it's not the case.

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Last edited by Oleksiy on Mon Jun 10, 2019 5:03 pm, edited 1 time in total.

gps1539
Posts: 42
Joined: Tue Jul 03, 2018 3:08 pm

Re: Some stats for the year of use

Mon Jun 10, 2019 3:30 pm

Doesn't look like your image was uploaded.

Oleksiy
Posts: 93
Joined: Fri Mar 23, 2018 4:30 am
Location: Kyiv, Ukraine

Re: Some stats for the year of use

Mon Jun 10, 2019 5:03 pm

Should work now, thanks

gt1
Posts: 350
Joined: Sat Nov 07, 2015 7:31 pm
Location: Baltimore

Re: Some stats for the year of use

Tue Jun 11, 2019 10:27 am

The downward trend is worrisome.
I forgot, have you explained how you capture the data?

Oleksiy
Posts: 93
Joined: Fri Mar 23, 2018 4:30 am
Location: Kyiv, Ukraine

Re: Some stats for the year of use

Tue Jun 11, 2019 11:10 pm

All data are captured from the dashboard and instrument panel. I take photos of SOC and ambient temperature when I depart and arrive home, otherwise only temperature when in between trips. Once a day, usually upon arrival, I also get Batt.Kapa, Batt.Ladung and battery temperature data from hidden menu, and also make a screenshot of the mileage, efficiency and average speed info for the day.

gt1
Posts: 350
Joined: Sat Nov 07, 2015 7:31 pm
Location: Baltimore

Re: Some stats for the year of use

Wed Jun 12, 2019 12:27 pm

What can I say, you're a thorough and patient man.

Oleksiy
Posts: 93
Joined: Fri Mar 23, 2018 4:30 am
Location: Kyiv, Ukraine

Re: Some stats for the year of use

Thu Aug 29, 2019 4:48 am

I've done the battery re-initialization in my 2015 BEV recently, so the stats are going to be skewed for some time. Hence sharing my previous logged data for over one year of use and 29K km driven.

- All data points are monthly averages of daily logs (days I drove the car). I logged data before the charges. The data is sourced from the trip computer , dashboard and "hidden menu".
- Ambient temperature is the average for the trips, so may differ a little bit from the whether history for my location (Kyiv, Ukraine).
- The range estimate is calculated as follows. Suppose, I drove 108 km yesterday, started from 100% SOC and arrived with 35% SOC remaining. I divide 108 km by 65% (depth of discharge) to arrive at 166 km range estimate for this day. The result is more robust the more km I drive during the day.
- The battery capacity estimate calculation: I take 108 km of my mileage for the day and divide it by 8.7 km/kWh average efficiency from the trip computer to arrive at 12.41 kWh energy spent. Dividing this number by 65% depth of discharge, I get the estimate of 19.1 kWh.[/list]

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So, based on the data, my battery capacity estimate went down from 18.2 in May 2018 to the current pre-reinitialization 16.4 kWh. The Batt.Kapa trend is very similar, albeit a lot smoother.

The range estimate is driven by the battery capacity and efficiency. It goes down in winter, and this summer is lower compared to 2018, reflecting the battery degradation.

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The efficiency is driven by average speed and temperature, the former being a very weak predictor in my case (maybe 'cos my average speed is quite stable). The temperature could be used for forecasting the efficiency (R-squared = 0.93).

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Obioban
Posts: 74
Joined: Wed May 22, 2019 6:16 am

Re: Some stats for the year of use

Thu Aug 29, 2019 5:30 am

That seems like pretty significant degradation, for the mileage!

Oleksiy
Posts: 93
Joined: Fri Mar 23, 2018 4:30 am
Location: Kyiv, Ukraine

Re: Some stats for the year of use

Thu Aug 29, 2019 5:55 am

Other 60Ah that I know of in Kyiv are in the same ball park. Also, I bought it used, so the total mileage is 34K miles / 54.5K km now.

Secondly, the i3's BMS is notorious of not knowing what's going on with the battery, degradation included. Most likely, it just guesses the level of degradation based on time / mileage, end preemptively cuts the bottom buffer by voltage. E.g., my car at 3% SOC showed 3.55V cell voltage (my report on this is here viewtopic.php?f=11&t=13535&p=56484#p56484).

I have 19.1 kWh Batt.Kapa now, after the reinitialization, the range estimate and battery capacity estimate went up accordingly. Will try to get closer to zero SOC to check the real level of degradation.

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