Better battery cooling.

I was watching the battery temp on my test run yesterday. The cabin temps were in the high80's. The battery got to 115 F. Even at temperatures of less than 100 on the battery, if the batterys are charged heavily for several minutes straight (long downhill full regen) the charge will get limited to 12-25 amps. A few minutes of non use and full regen returns. The limit is not MIMA related, as the regen with brake activation in normal IMA mode is limited the same way. I think it is nearly time to open my pack, check all connections for tightness, install a temp circuit on all of the subpack and then compare the temps under heavy use conditions to see if a subpack is getting hotter than the others. I can design a separate temp monitoring micro based system that watches all the pack temps, and sends the average to the MIMA processor, or possibily does the temp control for the fans and opens up the MIMA pins now used for temp and fan control for other functions. Engine rpm(NEP),and the brake switch, are the first signals on my wish list. :wink:

Some other ideas I had.

Idea #1
Using a Liquid Cooling system of some sort (that they use in computers). I have no knowledge on how effective this would be. The other aspect of this is that they normally plug into 110v AC, but the fans/pumps work on 12v ?.

http://www.coolerguys.com/alllicoit.html
for example.. one of the cheaper units
http://www.coolerguys.com/840556058205.html

If you had to put these metal things in direct contact on each battery cell... that would add up in cost quickly and make this prohibitive. If you could just string this tubing all around and suck up the heat... that would be a lot cheaper and easier to install. Added Ok, these metal things are heat sinks 1) you need them and 2) they need to be in nearly perfect contact with the object to be cooled. In addition, I've read that only 4 of the battery packs can be accessed easily so only 4 of ? could actually be cooled. This is looking like an expensive dead end.

Idea #2
Redirecting the passenger AC output directly into the Battery Area. Whether this is partial and/or full depends on what is set up. I figure you intercept the 'tubing' with a 'T' (45 degree angle?) under the dash and run it back there. The question is whether you are adding excess moisture at all (condensation would be a very bad thing I would expect).


Idea #3
Rigging up a mini cooler (the cooling part obviously) which uses the Peltier Process and cooling the battery compartment. It would plug right into the DC power plug. The question is whether you are adding excess moisture at all (condensation would be a very bad thing I would expect).
http://www.compactappliance.com/xq/...7/iProductID.6993/qx/shopping/product/P25.htm

The cheap $100 coolers don't freeze anything and in Arizona your humidity is almost nothing. So I'd be surprised if condensation is a problem there. New England or during a rainstorm (high humidity) is a different scenario! This table (in blue) gives you an idea what to expect for creating a condensation problem. Another issue is this is basically a heat transfer, the inside get colder and the outside gets hotter so the interior of the car is going to get hotter while the batteries get cooler. That's a potential problem for the driver and perhaps would require the vent behind the passenger seat to be blocked off? That wouldn't be a big deal if you operated this when not driving (just keeping the batteries cool). Also... this little appliance will suck your battery dry (it will keep on working in the Insight after you turn the power off; however it doesn't do this in the Pilot.. check other threads on battery usage for details on this phenomenon), but you can buy an attachment that 'cuts out' when it reaches a certain point to mitigate that. This battery sucking thing may make this whole thing a moot point!

Whether condensation occurs, depends on the temperature of the cooled object, on the ambient temperature, and on the air humidity. Here is a table that will give you an indication whether you are risking condensation problems:

Air humidity . /
Air temperature 30% 35% 40% 45% 50% 55% 60% 65% 70% 75% 80% 85% 90% 95%
30 C° 10,5 12,9 14,9 16,8 18,4 20,0 21,4 22,7 23,9 25,1 26,2 27,2 28,2 29,1
29 C° 9,7 12,0 14,0 15,9 17,5 19,0 20,4 21,7 23,0 24,1 25,2 26,2 27,2 28,1
28 C° 8,8 11,1 13,1 15,0 16,6 18,1 19,5 20,8 22,0 23,2 24,2 25,2 26,2 27,1
27 C° 8,0 10,2 12,2 14,1 15,7 17,2 18,6 19,9 21,1 22,2 23,3 24,3 25,2 26,1
26 C° 7,1 9,4 11,4 13,2 14,8 16,3 17,6 18,9 20,1 21,2 22,3 23,3 24,2 25,1
25 C° 6,2 8,5 10,5 12,2 13,9 15,3 16,7 18,0 19,1 20,3 21,3 22,3 23,2 24,1
24 C° 5,4 7,6 9,6 11,3 12,9 14,4 15,8 17,0 18,2 19,3 20,3 21,3 22,3 23,1
23 C° 4,5 6,7 8,7 10,4 12,0 13,5 14,8 16,1 17,2 18,3 19,4 20,3 21,3 22,2
22 C° 3,6 5,9 7,8 9,5 11,1 12,5 13,9 15,1 16,3 17,4 18,4 19,4 20,3 21,2
21 C° 2,8 5,0 6,9 8,6 10,2 11,6 12,9 14,2 15,3 16,4 17,4 18,4 19,3 20,2
20 C° 1,9 4,1 6,0 7,7 9,3 10,7 12,0 13,2 14,4 15,4 16,4 17,4 18,3 19,2
19 C° 1,0 3,2 5,1 6,8 8,3 9,8 11,1 12,3 13,4 14,5 15,5 16,4 17,3 18,2
18 C° 0,2 2,3 4,2 5,9 7,4 8,8 10,1 11,3 12,5 13,5 14,5 15,4 16,3 17,2
17 C° -0,6 1,4 3,3 5,0 6,5 7,9 9,2 10,4 11,5 12,5 13,5 14,5 15,3 16,2
16 C° -1,4 0,5 2,4 4,1 5,6 7,0 8,2 9,4 10,5 11,6 12,6 13,5 14,4 15,2
15 C° -2,2 -0,3 1,5 3,2 4,7 6,1 7,3 8,5 9,6 10,6 11,6 12,5 13,4 14,2
14 C° -2,9 -1,0 0,6 2,3 3,7 5,1 6,4 7,5 8,6 9,6 10,6 11,5 12,4 13,2
13 C° -3,7 -1,9 -0,1 1,3 2,8 4,2 5,5 6,6 7,7 8,7 9,6 10,5 11,4 12,2
12 C° -4,5 -2,6 -1,0 0,4 1,9 3,2 4,5 5,7 6,7 7,7 8,7 9,6 10,4 11,2
11 C° -5,2 -3,4 -1,8 -0,4 1,0 2,3 3,5 4,7 5,8 6,7 7,7 8,6 9,4 10,2
10 C° -6,0 -4,2 -2,6 -1,2 0,1 1,4 2,6 3,7 4,8 5,8 6,7 7,6 8,4 9,2

All values are in °C.
Example for using this table: Ambient temperature=20°C, air humidity=65%. Result: Condensation will occur at a surface temperature (CPU, Peltier cooler) of 13.2°C

This table is copied from this website: Page 4 http://www.heatsink-guide.com/peltier.htm. In fact there might be a lot of other interesting things (beyond Peltier) about cooling there as well. Perhaps the same idea that doesn't use the Pelier process would work better. I'm going to check it out and will post again if i find something.

CABIN/CONTROL CABINET POWER VENT MOD

I got the fans mounted to the plastic vent grill behind the passenger seat. All thats left is to get a male aux. power plug from auto parts house, which I will do today. I will begin collecting data on the commute tonight. What I will get is the difference between cabin temps and BAT/MPI temps with the new vent fan running. We already have data without the fan, as that is the data I had previously collected. I have a temp probe (per Mike) on both the BAT and MPI locations.

I removed the plastic vent from the carpet, and cut out the grill portion in the middle of it. I will take this opportunity to say that the little grill is ONE_OVER_ENGINNERED_PIECE_OF_HARDWARE. Unless its part of the SRS . I mounted two (2) 80 MM case cooling fans to the face of the modified grill frame, and ran the wires under the carpet up the center console to the front. I'll hardwire them in later with a switch.

It might be that a blower of some configuration...squirrel cage or centrifigal, etc........could provide a greater volume of air movement. Finding the right one to go behind the seat will be the limiter.

These fans add about 3/4 of an inch (20MM) of height to the vent grill. If there is a passenger onboard they will need to keep the seat clear of the fans.

The original grill is made with an angle to the openings. This angle is canted toward the inside of the cabin (the back of the passengers seat), instead of toward the passengers door. It is made to fit the carpet only one way. Looks like it would have been better to point the angled grills toward the door, as it is real easy to restrict the airflow to this vent in the stock configuration. Have you got anything in that pouch on the back of the seat . Maybe it was thought that the air near the window would be to hot :?:

Took plenty of pics, if it will help anyone send me a PM. (Until I get hooked up with a hosting page)

In a subterainian garage at approx. 70 deg. F, I noticed that the battery pack temperature increased by about 3 deg. F in about a 2 hour period. This is with all power off, and with the car windows open.

This observation would suggest a large thermal inertia of the Insight battery pack.

While in some parts of the world, the ambient temperature of the Insight interior in a parking lot in the summer, despite the best radiation-deflective efforts, can reach the upper limits of optimal perfomance and longevity for the battery pack, modifications to the sub-optimal stock cooling system, like those in the MIMA_C system and Highwater's previous message would seem to be worthwhile investments.

For those who may not have followed the details of this and other related threads, the Insight battery pack cooling fan doesn't remain on during auto-stop, possibly to maintain the "silence" of the situation.

From my observations and that of other MIMA modification users, the auto-stop condition is often where forced convective battery pack cooling is most necessary and effective.

Mike is right about my commute, and I certainly want to make sure folks understand that my given conditions are most likely quite different than most. I drive at 11PM and return at 9AM, never seeing much intense direct sunlight, as I park in the garage at home.

I have also observed that thermal inertia with the 144 volt pack.

For a qiuck summary of what I am seeing with this vent fan behind the seat, the battery temps are staying within a couple of degrees(F) of the cabin temps, and also quite often end up less than the beginning of the trip. Prior data indicates battery temps as much as 12.0 more than cabin and only once was the battery temp less at the end of trip and that occured when the cabin temp had dropped about 10 degrees. I use some assist on quite a few hills and get all the regen I can on deceleration, so the battery sees a little activity. I intend on working the battery more when I get MIMA.
I will put a couple more trips on tonight and post some actual figures tomorrow.
I would think that those units seeing daylight might benefit more than my data indicates, but it certainly looks like putting more_GOOD_air into that little vent is a_GOOD_thing. The MPI temp is also realizing some good out of this.

My fans are the 80mm size, so there might be some smaller fans that would fit inside the vent frame after the grill is cut out, providing a lower, flush profile, just a thought............

Guys
I took some aluminum duct tape, some reflectrix attic insulation, (bubble wrap with aluminum on each side)and made a duct that goes from the AC exhaust on the passenger side, across the bottom of the dash, takes a corner, goes down on the passenger door pillar, then fits between the seat and door jam, then finally expands and is stuck to the plastic battery inlet vent. All out of the way so the seat can slide back and forth. All the way back still bumps it , but it is flexable so that don't matter.I made a 100 mile round trip, with lots of mima use. The battery emp got to 113 at the max. with the cabin temp at 77. The AC being on, dropped the inlet air to 55 degrees, and was making the car too cold as I had the blower on full. I turned off the AC and tried just the blower. The result was that the battery did respond by staying at the 113 temp, and cooled down when no assist or regen was happening, but not as fast as I would have expected with so much air flow(I could hear the rear fan speed up when the blower was turned on)and at such a large differential in temp. 55 to 113 is a lot.
Conclusion! the battery pack cooling is a joke. I should have been able to cool that mass much faster than It was able to, especially with the cold air, and the booster blower.
I wish I had a prius pack configured so I could just drop it in, and set up a good cooling system. I am sure I could do better than the poor Insight pack. The circumfrence of the duct was 8 inches.
:wink:

Well sounds like we might be barking up the wrong tree here, since the thermal inertia is significant with the MIMA usage, that is if your going to do MIMA, but I will post the afformentioned temp data for whatever good it may be. The temps are in (F) and are the differencial from cabin temps.

Perhaps in the winter we would want the battery cabinet vented into the passenger compartment or pushed back through the secondary duct into the defroster :?:

BEFORE VENT FAN
TIME MPI BAT
11PM 36.3 11.8
9AM 20.9 2.7
11PM 36.6 7.6
9AM 16.1 2.1
11PM 36.7 10.2
9AM 17.0 1.0
11PM 45.1 8.2
9AM 13.1 -7.4
11PM 40.3 10.8
9AM 14.9 -0.2
11PM 47.5 10.2
9AM 13.7 -3.6
11PM 45.9 12.2
9AM 16.2 -0.9

AFTER VENT FAN
11PM 39.0 1.6
9AM 23.5 -0.6
11PM 35.5 2.4
9AM 16.9 -1.9
11PM 33.8 3.2
9AM 23.2 0.3
11PM 40.3 2.3

Noticable improvement under my current driving conditions, is the lesser values of the battery temps on the 11PM drive. Used to be an increase of 10 degrees, now along the line of 2 degrees(F).
Randall
Sorry about the tight fit, I couldn't get the data to paste in like i wanted.