Solar powered cooling fan mod

Discussion in 'Honda Hybrids' started by msantos, Jun 14, 2009.

  1. Daox

    Daox Well-Known Member

    Any thoughts on getting higher flow fans? The 120mms blow 75-80 cfm each.

    Nice work BTW, I like it!
  2. Maxx

    Maxx He who posts articles

    I think this idea is great. Glad to see some good wholesome ingenuity!
  3. msantos

    msantos Eco Accelerometrist

    Ahh, yes. More is indeed better. :D

    But in this case, we would need much more solar power than the barely 5W I have available. A larger solar panel would also be heavier and at some point the losses will start chipping away at the big picture.

    When it comes to fans its a fine balance as well. A high CFM fan will have a higher power rating and most of the high CFM ones will require 250mA or even more !!!:eek:

    A 120mm fan that consumes only 80mA can be had from the same source and brand but it would not be as much of a good fit as two 80mm.... and 2x80mm still push more CFM than a single 120mm.

    As you can almost tell, two 80mm side by side match nicely in size with each venting outlet. Almost a perfect fit.

  4. msantos

    msantos Eco Accelerometrist

    OK, one more last update. As it was Canada Day, I left the car out on the driveway since 9:00 in the morning up until this evening... and along the way I took a couple of measurements.

    The following shows the car's temperature on the inside and the OAT as well sometime after 2:45 PM :


    The test results:

    The outside temperature was recorded at 27C (80F), and the interior temperature of the passenger cabin with the fans ON was observed at 34.8C (94.64F).

    The car still felt warm when getting inside, but it was not as HOT as it would feel on a regular summer day. I believe that if I had used a windshield shade, the results would also have been better... but that level of testing is for another time and place.

    Anyhow, I hereby declare this mod as viable and despite it not being able to cool the cabin even further, it is even more appealing because of its "low cost and high fun" factor.

  5. Skwyre7

    Skwyre7 Well-Known Member

    I give you a :thumbs_up:, sir.
  6. ematzen

    ematzen Well-Known Member

    So, as a bit of a layman, I can make this system even simpler, correct? By not interacting with the battery whatsoever, and simply using all the power to power the fans? Any recommendations? Thanks.
  7. psyshack

    psyshack He who posts articles

    For kicks just find a cheap panel and cheap fans. Wire them up direct and play with it in the sun. Then place the panel on the rear window package shelf and see how the fan runs. You do have tint,,, right.

    The only reason I have not done this mod is because the car is tinted. And I don't know how much the tint will effect the panel.

    The over all idea is very sound and good.
  8. ematzen

    ematzen Well-Known Member

    Yeah, I'm curious about tint too. I have pretty extreme tint. I have everything ordered, a 5watt panel, four fans. We'll see. I'll keep you posted.
  9. ematzen

    ematzen Well-Known Member

    Well, I installed the solar powered cooling fan mod. 5 watt panel. Only installed 2 fans (on the drivers side). Connected a third to see how it runs, and the speed dropped dramatically. I think the tint plays a pretty large impact on the solar efficiency, however, it still works pretty well. The fans spin fast.

    So, all in all, it seems like a success, though I have my doubts as to whether it will make much of a difference. We'll see. Unfortunately, today's pretty overcast, so we won't know.

  10. msantos

    msantos Eco Accelerometrist

    Hi Evan;

    Awesome news. from what I gather, the initial attempt was a practical success since you managed to get one pair to spin with an overcast sky.

    In those situations it is unlikely that additional fans added in will help. That is why I have a switch inside the trunk that prevents the second set fans from spinning when the solar power is not enough. On a very sunny day, all four fans will spin like mad -- which is a good thing. ;)

    Now, provided that trunk lid is sealed well (make an air tightness test by locking yourself in the trunk with a thin foil strip in your hand while someone closes the driver's door. If the foil and the vent vanes move a bit then all is fine). Look for mis-aligned the rubber seals around the doors and the trunk lid just to be sure.

    Overall, the key is to ensure some form of air flow exists even if it appears very little. :)


  11. psyshack

    psyshack He who posts articles

    Sounds good! :)
  12. psyshack

    psyshack He who posts articles

    This what I'm looking at for the HCHII.



    I can even go to these and have head room.
    For two more CFM per fan.

    I feel good about the fold up panel. Just mount it with velcro on the package tray. Basic research is telling me I can power fans and maintain the 12v. Or shut the fans down and use the panel to charge a cell phone or other device. As much as it pains me. I can tell if I have a cell plugged in and charging when driving the HCHII. Or listening to music off the past ipod or the current iphone. So the panel gives me operation options but also portability.

    The fans are at/near rock bottom pricing. And I like trading with Jabtec. I need to shop the panel more. I have not got into the switches yet. Price is not a problem concerning them. I would like to be able to switch from the native 12v to the panel on dash and consul power ports and the 12v under the hood.

    Just thinking with finger. :)

  13. msantos

    msantos Eco Accelerometrist

    Awesome stuff Jeff. :D

    BTW, roughly a week ago I purchased a collection of flexible monocrystaline panels (@ 10W each) that I will use for the 2010 Prius just to make up for the hatch constraint.

    In total I hope to have 20+Watts worth for the Prius and 10+Watts for the HCH-II. I'll post some pics as soon as I have a chance.


  14. greenrider

    greenrider Well-Known Member

    Here's a question. I purchased a few of the clear plastic covers for A/C and heating vents for my home this winter. They are shaped plastic, and similar in shape to a piece of quarter round, except plastic to direct air flow out of floor or ceiling vents.

    Except on the most unbearable days of the summer that necessitate A/C, I simply keep my windows part-way or more open when driving. If I was to fit one of these plastic directional units over the IMA vent on the back deck of the HCH II, would it possibly yield an improved airflow through the pack?

    I'm thinking about something similar to this

    but in the right size.
  15. pasadena_commut

    pasadena_commut Well-Known Member

    Were there fan guards over the blades when the installation was completed?

    What was the material covering the vents originally? Hard to tell from the picture if it was rubber, perforated metal, or whatever. Whatever it was, what was it's purpose? The fans are very much the equivalent of an open hole, so if the original covers actually did something beyond cleaning up the look, the fans are probably not doing that job now.

    Interesting modification, but I have to wonder, in terms of keeping the inside of the car cool, how it compares to cracking the back windows slightly. While low tech, opening the windows does have the distinct advantage that it lets the rising hot air just keep on moving right on out of the car. Balanced against the disadvantage that it lets dust, rain, and bugs in, and is a bit of a temptation for thieves.
  16. msantos

    msantos Eco Accelerometrist

    No, I did not use any fan guards over the fan blades in this application and also not on the similar operation I had done this summer on my 2010 Prius. I will post the pics of the mod on my 2010 Prius as soon as I have a chance in the Prius section.

    If you check on page 2 you'll see that the vents were generally blocked by horizontal lightweight rubber vanes (like gravity shutters) and it does not take much to get them to swing open. They swing only in one direction (outward) which means that if you create positive air pressure inside the vehicle the vanes will let air out but will not allow air in even if a negative pressure exists inside the car.

    The fans create air pressure against the vents which will then create a slight negative air pressure inside the car. The idea is to let the air flow into the car through the font dash cooling ducts (through which the AC travels) for the purpose of not letting them warm up as much as that would force more AC and energy to cool off the car properly when it comes time to drive away. Again, we're talking about 80-160 cubic feet per minute of air movement which amazingly works quite well. Frankly, it works better than the OEM solar cooling the higher trim Prius comes equipped with from the factory.

    Anyway, leaving the windows cracked open will work very well too but it will also often allow some dirt, dust, rain to enter the car as well as the occasional thief looking for an easy car to break into.
    Needless to say, this mod will find its way into every new car I buy. No exceptions.


  17. pasadena_commut

    pasadena_commut Well-Known Member

    I bet in normal use (not your fan mod, just the stock vanes) they only open once the car is moving fast enough to develop a low pressure area behind the car.

    Axial fans tend not to work very well against pressure gradients. Unless those vanes are feather light, pushing them open is going to create back pressure. So the fans most likely are not delivering their full flow rating. To the extent that the inside car pressure drops this will also act to reduce outward flow. (Except with the front vents open I doubt there is enough pressure change inside the car to even measure.) So it may be that some sort of mechanical shutter opener might improve performance, in terms of increased cooling for the parked car. Before worrying more about such a mechanism it would be interesting to know how large the effect is. If you can reach the outside of the vanes to prop them open, so that the fan pressure doesn't have to do this work, you may be able to measure an increase in flow out of the car. (Clearly propping the vanes open when the car is running would be a bad idea, forcing them open would only be for when the car is parked and turned off.)
  18. RudyHMPG

    RudyHMPG New Member

    I have noticed that these vehicles tend not to like hot weather. I just bought mine a week ago. I live in MI where we experience all the seasons. I am concerned about the summer as the battery is aging. I got almost 80K so far, and AFAIK the battery has not been changed.

    Where did you get the flexible ones. Does it just roll right up? for easy storage?
    This looks like an easy improvement.
    So you also have this charging the 12 volt starter battery too?
    The switch was a nice touch, can you provide a picture of where you mounted that?
    I had no Idea we could mount fans there, that looks like it was almost meant to use those fans.
  19. msantos

    msantos Eco Accelerometrist

    Hi Rudy;

    Yes, as we have mentioned over the years, these cars walk a fine line between good MPG and energy deficits so anything we do to reduce the deficits will only improve the efficiencies... and the more you do, the more measurable the improvements will be.

    In reality, this solar mod tackles three major objctives:

    1. Reliability. Helps keep the 12V battery charge at optimum levels and therefore significantly improve its lifespan
    2. Comfort. Helps keep the car cooler which then reduces the need for additional/agressive cooling measures before driving away. Ironically you WILL often prefer to leave the car properly positioned under some Sun to keep it cooler. :D
    3. FE. Helps increase overall MPG due to reduced AC demands and 12V charging demands

    I secured these flexible panels from a pacific rim manufacturer that at the time also had an eBay outlet. As seen in this picture, the panel is very thin and lightweight but with an aluminum backing that still allows some flex. No it is not a roll-up but in my view this is an ideal format for automotive applications as it is robust and can be installed over mildly curved surfaces without an issue. It also helps a whole lot that it weighs very little.


    Then, the main switch location in the dash. It always lights up if it is turned on which indicates there's power being routed to the cooling fans. Still even with the slightest ambient daylight, the 12V battery will always be receiving a charge which I measured in the 50-150 mA in cloudiest days. In sunny days we have enough power to more than keep the 12V battery charged... AND still power 4 cooling fans at full throttle. :D


    By the way: Did I say that every new car I get will have this mod? Well, this is my rule going forward.


  20. flyer351

    flyer351 Member

    I'd like to resurrect this thread to ask a question. I now have 30 watts worth of mono crystalline panels driving three different fans in the trunk area. While the mod works fine I wonder if there's room for improvement. The Prius solar panel roof drives the main blower for the cabin. With 30 watts, I'm approaching the same wattage capability as the Prius.

    The blower connector on the HCH is conveniently located just below the glove box. There are only two wires going into the connector for the blower. Would it be possible to simply tap into these wires to feed power to the squirrel cage blower fan?


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