Questions regarding the Mercedes B-Class Electric kWh

[jlsoaz]

[edited to correct for usable kWh and link to Tony Williams' points, and a couple of other things.]

Hi - I can't figure out where to post this or whether an answer has been posted. I've been trying better to understand the claims as to the kWh of the Mercedes B-Class Electric vehicle. I think Tony Williams indicates 36 kWh, with 31.5 usable. Is this firm?

http://www.mybclasselectricdrive.com/forum/viewtopic.php?f=8&t=327" onclick="window.open(this.href);return false;

One of the things that is confusing to me is this business of opting to charge up to a higher amount. Does that mean that one is charging to 36 kWh or to 31.5 kWh? Is that optionality still part of the car? It seems similar to my 2012 Leaf (I normally charge to 80% but sometimes charge to 100%). I've never really verified - for my Leaf, if I charge to 100%, I'm guessing this is not 24 kWh, but rather charging to ~21 or 22 kWh?

Lastly (and I guess keeping in mind the involvement of Tesla in the Mercedes Powertrain) are there analagous option-to-charge-to-a-higher-amount features on the Tesla Model S?

 

[TonyWilliams]

Mercedes B-Class ED battery

Just reset the data and you'll get the range of the GOM to a "rated" standard at 3 miles per kWh consumption. The battery needs to be near room temperature.

Mercedes B-Class ED battery

36.0kWh total – 100% SOC (never used)
31.5kWh usable- 90.0% SOC (default 3 miles per kWh * 31.5 = 94 miles)
28.0kWh usable- 80.0% SOC (default 3 miles per kWh * 28.0 = 84 miles)
1.0 kWh unusable- 2.7% SOC

*** Mercedes consumption meter is calibrated so that 3.6 miles per kWh will show as 3.0 on the dash, as will 3.0 miles per kWh show as 2.5 on the dash. The correction factor is 83.333%, or 1.2

As the battery degrades over time, those mileage figures will drop. Also, know that if your car's battery is at room temperture, you can reset the GOM and know that whatever miles are shown with a "full charge" (either normal 80% or extended charge at 90%), if you divide by 3, that is the usable kWh.

Then , you can calculate the degradation over time. At 87 miles shown with a extended charge, 87 / 94 = 92.5% of new capacity. Of course, we don't know yet what other manipulation that Daimler / Mercedes does with degradation data, yet.

**********

The published voltage range 4.2v to 2.5v, which is 3.35v average.

3.35v * 2900mah * 3696 cells = 35.9kWh

88 in series, 42 cells per 4.15v module

365.2 volts @ 4.15v
369.6 volts @ 4.2v

 

[jlsoaz]

Mercedes B-Class ED battery
[...]

Ok, thanks Tony.

 

[TonyWilliams]

Range at 65mph (100km ground speed) on dry, hard surface level road with no wind or cabin climate control with new condition battery at 70F, battery capacity is "useable" amount, not advertised amount. Ranges are at maximum available charge and EPA rating is the maximum published.

Nissan
LEAF - 4 miles per kWh (250 wattHours per mile) * 21.3kWh = 85.2 miles / EPA 84

BMW
i3 - 4.7 miles per kWh (213 wattHours per mile) * 18.8kWh = 89 miles (the "REx" version has less electric range)

I3 "REx" (with gasoline engine) - 4.6 miles per kWh (217 wattHours per mile) * 18.8kWh = 86 miles minus reserve held for gasoline engine operation = 80 miles

Kia
Soul EV - 4 miles per kWh (250 wattHours per mile) * 27kWh = 108 miles / EPA 93


VW
eGolf - 4.1 miles per kWh (244 wattHours per mile) * 24kWh = 100 miles

GM / Chevrolet
2014 Spark EV - 5 miles per kWh (200 wattHours per mile) * 19kWh = 95miles / EPA 82

2015 Spark EV - 5 miles per kWh (200 wattHours per mile) * 18kWh = 89 miles / EPA 82

Mercedes
B-Class ED - 3.6*** miles per kWh (278 wattHours per mile) * 31.5kWh = 113 miles / EPA 87
*** Mercedes consumption meter is calibrated so that 3.6 miles per kWh will show 3.0 on the dash. The correction factor is 83.7%, or 1.2

Toyota
Rav4 EV - 3.4 miles per kWh (295 wattHours per mile) * 41.8kWh = 142 miles / EPA 113