Why different air ducts depending on seat heating?

[kd7iwp]

I was looking at a diagram on realoem and was surprised to see two different part numbers for the front air duct depending on whether there is seat heating. Can anyone chime in on why this would be? I imagine seat heaters can't use more than 100-200 watts so I don't see how there would need to be extra cooling required for any of the electrical systems.



Edit: Looks like I wasn't the first to ask this question https://www.mybmwi3.com/threads/forward-cooling-radiator.5782/

 

[alohart]

I was looking at a diagram on realoem and was surprised to see two different part numbers for the front air duct depending on whether there is seat heating. Can anyone chime in on why this would be?

I have never been able to imagine an explanation.

Edit: Looks like I wasn't the first to ask this question https://www.mybmwi3.com/threads/forward-cooling-radiator.5782/

The final comment in this thread is incorrect: whether the louvers are present isn't a REx vs. a BEV thing; it is a seat and battery pack heating option thing as indicated on the realOEM Website. Our former 2019 and current 2021 U.S. BEV's, both with the seat and battery pack heating option, have louvers while our 2014 BEV without this option did not.

 

[kd7iwp]

I didn't know there was a battery pack heating option (I thought it was standard equipment to have battery pack heating). If it's combined with heated seats perhaps it is some type of cold weather package? I imagine the battery heater takes a fair bit of current and I'm unsure if it runs off high voltage or 12 volts, I'm guessing high voltage. Trying to think if the DC/DC converter has to work extra hard for battery heating hence requiring the electronics to need extra cooling and hence a different air duct up front to cool that down through the coolant loop that runs to the back?

 

[alohart]

I didn't know there was a battery pack heating option (I thought it was standard equipment to have battery pack heating).

Living in the tropics, I have no need for seat or battery pack heating, so I didn't want to pay for this option when I bought our 2014 i3 BEV new. This option became standard in U.S. i3's in 2015, I believe, so I did not have a choice when I bought used 2019 and 2021 i3's.

If it's combined with heated seats perhaps it is some type of cold weather package? I imagine the battery heater takes a fair bit of current and I'm unsure if it runs off high voltage or 12 volts, I'm guessing high voltage. Trying to think if the DC/DC converter has to work extra hard for battery heating hence requiring the electronics to need extra cooling and hence a different air duct up front to cool that down through the coolant loop that runs to the back?

A problem with that logic is that i3's without this option don't have louvers so probably have slightly greater airflow through the front heat exchangers. Why would i3's with this option close these louvers when the heat seater is off as another i3 owner indicated (haven't verified this myself)? Closed louvers might reduce the drag coefficient slightly, but that would benefit all i3's.

 

[kd7iwp]

A problem with that logic is that i3's without this option don't have louvers so probably have slightly greater airflow through the front heat exchangers. Why would i3's with this option close these louvers when the heat seater is off as another i3 owner indicated (haven't verified this myself)? Closed louvers might reduce the drag coefficient slightly, but that would benefit all i3's.

Ah great point. I didn't consider the fact that the version without automatic louvers are always open.

TIS describes the louvers but doesn't associate them with battery heating or seat heating.