Passive cooling ?

You can drop up to 5 degrees C fairly quickly if you direct 50% of the air to the traction battery with the A/C system on high---you can send 100% of it to the pack if you wanted to. Over time the pack temperature will drop to the cabin temp. Looking at the battery sensor positioning in the pack I think you are actually reading a mixture of the cell temperature and the surrounding air temperature. If you start out with a pack sitting at a stable temperature (the canion reporting one temperature for all 66 sensors) you will see groups of three sensors cooling faster then the next group and so on. The cells are pretty large in size and therefore retain heat (or cold) for quite a while. If you were charging on L2 you could "pre-cool" the cabin and direct air to the battery to give yourself a head start on the cool down. As far as the factory battery fan is concerned---forget about using it for anything. The cabin A/C blower supplies more then enough air to pass through the small vent that exits the battery fan. The battery fan is driven by a PWM (pulse width modulation) motor that gets its speed signal from the BMU. It is the BMU that runs the fan for a few seconds and then shuts down after a self test and also to provide some air to clear anything out of the filter on the discharge side of the fan. Beyond that, if the fan is needed, the EV-ECU sends a CAN buss signal to the BMU to run the fan under certain conditions when charging. It is way too difficult to figure out what CAN signal is used to control the fan. Next time I have the pack out, I'm going to take the fan out as it is just blocking the exhaust air provided by the A/C blower.

As far as passing battery pack air back into the cabin instead of discharging it outside through the fan, I think it is a good idea. If I was going to do this with my car, I would cut an opening under the rear seat near where the tire repair kit sits. This is the high point on the battery above the rear bank of modules. Forward of that, you would be exhausting the air before it reached the back. It is also directly above the "bump" in the pack that holds the fan. A good connector for this purpose would be to use a boot like the one that surrounds the high voltage interlock to seal the top of the pack to the interior floor.

Thank you, siai47. Keeping them cool is the key to preserve the autonomy. I´ll try it my self im my i-MiEV.

siai47 said:

Yes, the picture marked "actuator" is the actuator in question. The quick and easy way to get instant cooling is to remove the connector and take the two screws out that hold the assembly to the heater duct. Manually move the linkage until the lower arm faces forward and you are done.

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There you go: pic 1 - air going to the footwell, pic 2 - air going to the battery pack. (the yellow deposit is grease)

siai47 said:

Yes, the picture marked "actuator" is the actuator in question. The quick and easy way to get instant cooling is to remove the connector and take the two screws out that hold the assembly to the heater duct. Manually move the linkage until the lower arm faces forward and you are done.

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I love this topic and Idea. Long history with EV's and batteries. The first EV's using lithium batteries were radio controlled airplanes and later helicopters. A hobby and passion of mine. Temperature and battery life are joined at the hip, it's that simple. With lots of experience abusing Lipoly batteries in sport planes (full discharge in as little as 6 to 8 minutes of flight, then charging at 2C to keep something in the air for most of the morning). I started charging hot batteries coming out of the planes in a small lunch cooler lined with those frozen ice substitute blocks. The other guys at the field laughed at first until my battery replacement costs reduced by 2/3rds. Now it's common practice among the pilots.

So back to the iMiev. I didn't like the idea of removing parts. I loose things when put away in a "safe" place. So I did some research on the actuator. Turns out it is not smart at all. I unplugged it and used a 9 volt smoke detector battery to trick it into moving to the full air to the battery duct position. Negative to the top pin and positive to the bottom one and it moves the damper to the floor vents closed, battery duct open position and stops. So all I need do is leave it unplugged. Everything is still where it belongs in the car so I can't misplace them. Due to the inventiveness of those on this forum and my own simplifying twist on an already good idea. I'll be cooling my battery while driving all, long, hot summer long! I applied the 9V power to the actuator pins with meter probe leads which was a bit tricky. I plan to get a copy of the plug used on the cars harness (anybody know what it is???) for future use with the battery, since in the winter I will want that heat on my feet and the battery is better warmed some by waste heat from timely charging anyway. Plus coldish but not too cold is good for longevity of the pack anyway.

Aerowhatt

Aerowhatt, thank you very much for this. Does reversing the polarity return the actuator to its other position? Be great if you could snap a photo of the connector and we'll see if it's recognizable ... maybe available off a junked different Japanese car?

JoeS said:

Aerowhatt, thank you very much for this. Does reversing the polarity return the actuator to its other position? Be great if you could snap a photo of the connector and we'll see if it's recognizable ... maybe available off a junked different Japanese car?

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Yes it does. If you reverse the polarity it returns to the floor vent open, battery duct closed position and stops. Also if one plugs it back into the wiring harness plug and then turns on the key it closes the battery duct too. I'll get a picture of the plug at first opportunity.

Aerowhatt

Aerowhatt said:

JoeS said:

If you reverse the polarity it returns to the floor vent open, battery duct closed position and stops.

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Hmm, in both cases when it stops I presume it also opens the circuit to the actuator coil? I'm looking ahead as to whether a regular DPDT switch will suffice or whether it should be a center-off spring-loaded switch?

If it functions similar to linear actuators, there are limit switches that cut off power, even if external voltage is kept to the actuator. Is it possible to have a voltmeter read the car's plug to see if it times out and shuts off power?

I also wonder what the middle wire is for if the outside two are power.

PV1 said:

If it functions similar to linear actuators, there are limit switches that cut off power, even if external voltage is kept to the actuator. Is it possible to have a voltmeter read the car's plug to see if it times out and shuts off power?

I also wonder what the middle wire is for if the outside two are power.

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Inside it has arcs of copper sheet that a "brush" rides on when the brush runs out of arc the motor stops in the desired position. So it could have power to it all the time without any issue. Simple DTDP switch would work to change polarity because of it's automatic stop nature. It's a super simple device!

The center pin may not be used or if it is it most likely gives a feed back voltage that the actuator is in one position or the other. For this system I would guess that if it is used at all it would "tell" the system that the battery duct damper was in the open position for QCDC charging.

I couldn't get a read on the middle wire with a meter at all when I was looking into it. Once I got the result I was looking for without any errors or warning lights I lost my motivation to investigate the middle pin

Aerowhatt

Possibly the middle wire is a CAN wire?

Phximiev said:

Possibly the middle wire is a CAN wire?

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Decided to take the thing apart to see. There is nothing in there electrical but the copper arcs on a circuit board and brush like structures which ride on them. A small resistor between the motor poles. One of the outside pins goes directly to the motor (simple brushed DC motor driving a worm gear reduction). The other outside pin goes to a donut of copper plate. The two arcs are outside of it and the brush like structures bridge the two. So power to one side of the motor directly from one pin. Power to the other side of the motor from one of the arcs depending on the position of the arm which moves the damper. The center pin is "switched" by the brush connecting it to the live donut. This would presumably provide a feedback voltage that would persist if the actuator was jammed or did not move as designed for some other reason.

Aerowhatt

Does there appear to be a mechanism to break the electrical connection once the servo hits one of the end limits?

Could you upload some pictures of the inner works?

PV1 said:

Does there appear to be a mechanism to break the electrical connection once the servo hits one of the end limits?

Could you upload some pictures of the inner works?

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OOPs . . . The brush just runs off the end of the copper arc to break the circuit and stop the motor, simple and effective.

I did take some pictures. Dropped a screw reinstalling it so I also got pictures of the entire shift console naked. I'm deciding on a file host since I will be stuck with it for a while. This is the first forum I have participated in that didn't host photo uploads "in house". So I'll have Photos posted before long.

Aerowhatt

Ok so I finally have links for my photos of the inside of the vent actuator for those interested. I still can't seem to imbed the photos which I would prefer to do??

This first one is the actuator open but nothing removed yet.

View attachment IMG Battery vent damper acctuator.jpg


The next one is with some of the gears removed and the "circuit" board lifted up. The back of the actuator arm gear is visible with the "brushes" exposed.

View attachment IMG Battery vent damper acctuator2.jpg


The last photo is a close up of the copper arcs on the board. The brushes (previous photo) bridge the circle in the middle to the partial arcs until the motor turns the brush to the end of the arc opening one side of the circuit to the drive motor stopping it in the right position.


View attachment IMG 3.jpg

Aerowhatt, thanks for posting and the explanations. Sorry, can't help with Flickr photos - anyone?

Click the "share photo" arrow, select "BBCODE", and copy the link, then paste it into your post:


gives

IMG Battery vent damper acctuator by T Pope, on Flickr

misterbleepy said:

Click the "share photo" arrow, select "BBCODE", and copy the link, then paste it into your post:

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For the life of me I can't find it on flickr. Am I in the wrong view or something? Help misterbleepy Help!!

Aerowhatt

Ok, so the temperature yesterday hit 105 and we are driving the iMiev with the AC on and AC fan on full bore. After reaching our destination, I turned the AC off (but left the car turned on) and heard two distinct noises: one was the louder sound of a fan (apparently coming from the battery?) and the second, the softer, whiny sound of a pump from the back of the car.

After a minute or two, the fan stopped; the other continued until I shut the car off.

So?

Very interesting. I think nearly all of us hear the motor coolant pump run when driving the car or shortly after. I've only heard the battery when once when quick charging (probably comes on with the vent fan inside, but couldn't hear it over the quick charger), and I had to practically crawl under the car to hear it.

Did you have the servo removed or manually turned to the battery position?

There is also a fan up front that comes on for the AC if needed. I've heard this come on when the car isn't moving, but it shuts off shortly after setting off. If it's running, though, it'll shut off as soon as you turn off the AC, it won't stay running, unless the motor needed additional cooling. I don't know how the car behaves at higher temperatures. Mine's only seen 95 F at the most.

Did the fan sound just like it does when you plug in?

I will check these questions later this evening, except I have not touched the actuator. My wife is out running the iMiev at the moment.

Its another hot day...