Forward sheilds are down! Heater, AC, Power stearing Pics.

[Quixotix]

I've always wandered what Mitsubishi meant by "compressor" when they refer to the heater as "Electric compressor cabin heater". Apparently it doesn't mean anything.

Today I removed the front shields from the bottom of the car to see the heater. The heater is the aluminum box in this picture (looking toward the rear). I thought the AC system might be able to operate as a heat pump (thus "compressor"), but there are no connections between the heater and the AC. I also looked to see if the heater could get heat from the motor cooling system. The lines for the motor coolant can be seen just to the left of the heater box in this picture (the two olive-greenish tubes). However, there is no connection between the two systems.

In the next picture (looking forward), you can see the power steering motor in the upper middle of the picture. The silver item just below it is the steering rack. The lower silver unit is the AC compressor.

Here is the inside of the forward battery shield. The gray thing you see lining it is a metal mesh (stainless steel I think). I'm not sure of the reason for this mesh, but it does has a little plate and screw dedicated to grounding the screen to the car body (more on this below).

CAUTION: If you decide to remove the battery shield from your car, it has one hidden fastener. There are a bunch of small bolts and a few plastic push connectors that are visible, but the ground screw for the metal mesh has a cover over it. The cover is the small rectangle with the rounded corners that you see in the center of this last picture. The cover just pops off to expose the ground screw. If you don't remove the ground screw before you drop the main shield from the bottom of the car, then you will rip the metal screen off the plastic shield.

Also note, the black screws in the center of the plastic shield are shorter than silver ones on the rest of the shield. Don't put the long screws in the wrong place or you might poke a hole in the battery case.

 

[FiddlerJohn]

Quixotix, Great photographs. Thanks.

...I thought the AC system might be able to operate as a heat pump (thus "compressor")...

I though the heater was the A/C. I was wrong, also. Heat pumps don't heat well when it's cold. That's is a big, heavy 600W heater *** Correction 4.2kW PTC HEATER***. Below is an album with a few heater related snipets.
http://www.facebook.com/media/set/?set=a.2873223782092.2126522.1004832596&type=1&l=b8da2eaa7f

 

[jjlink]

Thanks for the pictures. Which motor coolant line is closest to the heater box (hot or cold line)?

 

[Quixotix]

Thanks for the pictures. Which motor coolant line is closest to the heater box (hot or cold line)?

I'm not sure but I think the cold line is closer. Because of the battery pack, I can't follow the lines back to the motor area. One line connects to the top corner of one end of the radiator. The other line connects to middle of the other end tank on the radiator. I'm assuming the lower connection is the cold one.

PS - It sure looks like the radiator is right out of the ICE car due to the large size of its inlet and outlet connections as well as it's overall size.

 

[hBridgeDriver]

Great pics, it is helpful to see what's under the covers.

Here's a link to a SAE paper describing the i-MiEV HVAC system:

http://www.sae.org/events/aars/presentations/2010/W2.pdf

From the pics and dates in the paper, it looks like they're describing the JDM version, not the NA one.

Has anyone looked at the power draw when preheating or cooling the car? Since the heater (5.0kW) or AC (4.5kW) both exceed the EVSE and charger power rating, it looks like full HVAC performance won't be available.

 

[FiddlerJohn]

...the heater (5.0kW) or AC (4.5kW) both exceed the EVSE and charger power rating, it looks like full HVAC performance won't be available ... both exceed the EVSE and charger power rating

Thanks for the SAE presentations. GREAT POST!



... Crickets



Background Research:
1.Positive Temperature Coefficient (PTC) heating elements have fast heating response times and plateau once the pre-defined reference temperature is reached, and thereby creating it's self-limiting properties. The rise in resistance is experienced within a few degrees centigrade. This attribute of the PTC results in a heating element that self-regulates to a pre-set temperature and automatically varies its wattage in order to maintain that pre-set temperature.

2.Other sources say iMiEV heater is 4.2 kW and A/C is 3.5kW. Both use variable amounts of power.

 

[hBridgeDriver]

I'm getting the impression that Mitsu is being quite conservative in their claims for the MiEV. Not a bad way to bring technology to market. The higher power levels referenced in the SAE paper could be for the heater or A/C in isolation, but the lower numbers might apply to the integrated system (possibly with some derating thrown in).

I've got a reservation on one, and am very interested in the preconditioning performance. My driving mix is a bunch of short trips, and it is a real pain with an ICE (Internal Combustion Engine) since the darn motor never even warms up in the winter. But if the preheat is limited to the output of a few hair dryers...then it won't be as nice as I hoped on a Minnesota winter morning.

Anyone have insight into how the battery warming system functions? I'm assuming it is using energy from the PTC heater (meaning less will be available to precondition the cabin). Is it taking the heated cabin air and uses that to warm the battery?

 

[FiddlerJohn]

I'm ... very interested in the preconditioning performance. My driving mix is a bunch of short trips, and it is a real pain with an ICE ... motor never even warms up in the winter. But if the preheat is limited to the output of a few hair dryers...then it won't be as nice as I hoped on a Minnesota winter morning.

Anyone have insight into how the battery warming system functions? I'm assuming it is using energy from the PTC heater (meaning less will be available to precondition the cabin). Is it taking the heated cabin air and uses that to warm the battery?

My brother, who lives in Minnesota, says a garage is a reliabilty requirement. Even a little power (say one kW) over time could raise the battery temperature if the heat loss is low enough. Mitsubishi sells a Cold Zone option, which includes a battery warming system and heated outside mirrors for an extra US$150.

When the battery is cold, it has less range and takes longer to charge. That might be okay if your trips are short enough.

 

[hBridgeDriver]

I agree that garaging will be necessary -- and I have them available at home and at work. The cold zone package is of course going to be a requirement up here! Trips are usually pretty short, under 20mi total/day.

However, if the charger only draws 3200 watts from a L2 EVSE, and assuming a very efficient charger (90% optimistic guesstimate), there's only 2880 watts available to: preheat the cabin, warm the battery, and possibly finish off any charging.

It doesn't seem like much, even inside a garage to keep it out of the wind. Thus my query to any owners who've had some experience with MiEV preconditioning performance.

 

[Quixotix]

I wish I could give you real wattage numbers for the preheat function, but I haven't tried to measure them. So these are just my impressions:

If you are charging with the stock level 1 charger (120 Volt), the preheat capacity is very limited. Even if the batteries are fully charged, the system doesn't seem to send much power to the heater. When the temperature was around freezing, the car would not get warm even after the full preheat cycle. I'd guess the interior temp. increased about 20 deg. F after 1/2 hour. The warming seemed significantly better when on a level 2 charger, but I only did that once and don't remember enough to give any more details.

One big unknown is if the car heats faster if the batteries are fully charged. It should, but my impression is that it didn't - I'm not sure.

 

[hBridgeDriver]

Thanks Quixotix. I was suspecting that preconditioning with the 120V L1 EVSE would be marginal at best.

I would think it would precondition faster if the batteries are charged. From this link (which has been quoted before) http://www.greencarcongress.com/2011/10/imiev-20111010.html the battery warming system diverts heat from the HVAC system (taking heat from the cabin), then exhausts it. They aren't clear, but I'll suspect they don't exhaust it back to warm the passenger compartment!