vipergts
Posts: 10
Joined: Tue Jul 27, 2021 10:46 am

Battery kappa

Tue Jul 27, 2021 11:35 am

What is this and how do I check mine?

alohart
Posts: 2425
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Battery kappa

Tue Jul 27, 2021 12:57 pm

"Batt. Kapa. max" is the German abbreviation for the maximum usable battery pack capacity. It is only a calculated estimate of the capacity that can vary with temperature and other factors, so any single measurement should not be considered accurate. Multiple measurements over a period of time increase accuracy. It can be found in the service menu.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

vipergts
Posts: 10
Joined: Tue Jul 27, 2021 10:46 am

Re: Battery kappa

Wed Jul 28, 2021 8:02 am

Thank you for that. Mine is at 13.2. How bad is that and how bad does it have to be for bmw to replace the battery under warranty? I get terrible range even charging at 220v. Summer is around 59miles and winter around 29miles.

alohart
Posts: 2425
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Battery kappa

Wed Jul 28, 2021 2:04 pm

vipergts wrote:
Wed Jul 28, 2021 8:02 am
Mine is at 13.2. How bad is that and how bad does it have to be for bmw to replace the battery under warranty?
The usable capacity is guaranteed to be at least 70% of the new usable capacity of 18.8 kWh which would be ~13.2 kWh. The usable capacity of your battery pack might be near that limit, but the inaccuracy of the Batt. Kapa. max value makes that uncertain. Unfortunately, BMW dealers seem to require a system software update before measuring the usable capacity, both of which the owner must pay for. In almost all cases, the usable capacity increases a bit after the software update and measurement, so I wouldn't waste money on the test until several Batt. Kapa. max readings drop below 12.5 kWh or so.

My opinion is that BMW is trying so hard to avoid replacing i3 battery packs that they have found a way to temporarily increase the usable capacity. I suspect but can't prove that the software update resets the BMS to default values so that the usable capacity appears to be higher than it actually is.
vipergts wrote:
Wed Jul 28, 2021 8:02 am
I get terrible range even charging at 220v.
Range is not affected by the charging rate, so your i3 should have the same range after having been charged at AC Level 1 (120 V), AC Level 2 (208-240 V), or DC Levels 1 or 2 (DC fast charging).
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

vipergts
Posts: 10
Joined: Tue Jul 27, 2021 10:46 am

Re: Battery kappa

Wed Jul 28, 2021 2:57 pm

Actually I do get less range charging on 120v. I have tested it leaving it on the charger for 3 days. Another thing I found out is that my car was a lemon law buy back so it has no warranty. Does that apply to the battery pack too? They did do a recall for me once. If I'm at 13.2 right now, I wonder if the reading is much lower during the winter as I get half the range I get in the summer time.

alohart
Posts: 2425
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Battery kappa

Wed Jul 28, 2021 4:48 pm

vipergts wrote:
Wed Jul 28, 2021 2:57 pm
Actually I do get less range charging on 120v. I have tested it leaving it on the charger for 3 days.
When you write that you get less range, I assume you mean that the range prediction rather than the actual range might have been less. The range prediction varies for all sorts of reasons so isn't a very accurate estimate of actual range unless one drives the same route at the same speed at the same temperature consistently.

Charging at 240 V will warm the battery cells more than charging at 120 V which could result in a higher estimated range when charging at 240 V. When you charged for 3 days, no actual charging was occurring for probably the final 2 days because the battery was full. Therefore, the temperature of the battery cells was likely the ambient temperature which might have been cooler than cells being actively charged at 240 V.

The high-voltage battery doesn't know whether it's being charged at 120 VAC or 240 VAC. The on-board chargers (there are two) boost and rectify the input voltage to the 360-400 VDC necessary to charge the high-voltage battery. The amount of energy added to the high-voltage battery pack, which directly correlates to actual range, is identical regardless of the charging method.
vipergts wrote:
Wed Jul 28, 2021 2:57 pm
Another thing I found out is that my car was a lemon law buy back so it has no warranty. Does that apply to the battery pack too?
I have no idea. That's a question for your dealer.
vipergts wrote:
Wed Jul 28, 2021 2:57 pm
If I'm at 13.2 right now, I wonder if the reading is much lower during the winter as I get half the range I get in the summer time.
The capacity does vary with temperature which partially explains lower actual and predicted range during the winter. Other reasons include more drivetrain friction and air resistance at cold temperatures and the use of cabin heating. I'm sure the official usable capacity is at a specified temperature (25 ºC?). The dealer will perform the capacity test in the shop where the temperature would be much warmer than winter outdoor temperatures.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

mybmwi3test
Posts: 1
Joined: Wed Aug 18, 2021 8:45 am

Re: Battery kappa

Wed Aug 18, 2021 8:47 am

alohart wrote:
Tue Jul 27, 2021 12:57 pm
"Batt. Kapa. max" is the German abbreviation for the maximum usable battery pack capacity. It is only a calculated estimate of the capacity that can vary with temperature and other factors, so any single measurement should not be considered accurate. Multiple measurements over a period of time increase accuracy. It can be found in the service menu.
Thank you, this is useful

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