Mimicing the Prius Solar Roof Cooling System - Fuel Economy, Hypermiling, EcoModding News and Forum

NoD~ · 05-07-2013, 09:42 AM

I have recently build a solar panel setup that will replace my sunroof. It should put out around 60w of power (18v+ from the panel, 13v+ from the charge controller). I will have this thing charging my car for all the right reasons, but one thing I REALLY would like to have is the feature that runs the car's squirl cage air circulation fan w/o having the key on, or the control switch clicked over.

Anybody have a good idea to help me wire that up? I've been clicking back and forth on different ideas on how best to set it up, but figured I'd ask you guys to see if you had any thoughts on the matter.

One of the best ways I could think of was this: Tap into the 12v output (to battery) directly to the fans + lead and have a large diode between the charge controller and the battery, so when the fan kicks on, it doesn't pull from the battery at all.

I realize this won't cause it to spin at warp speed as it will only be ~5amps of power, but if it's turning even on low speed, it's going to cool my car quite a bit.

To control the on/off of the fan, I have a few ways to do it. I do have an Arduino unit I could use to program and have the fan kick on only when the car hits X degrees. An easy way, perhaps temporary, is to have a relay activate when the key is off to enable the fan off the solar. The Charge Controller, unless mistaken, only puts out the 12v battery charge if it detects voltage on that end for a battery to be charged.

Anywho, throw me whatever ideas you might have to make this work. I'm still working on an acrylic sunroof and mounting everything up, so I'm not quite there yet... but I like to try and plan ahead.

Phantom · 05-08-2013, 03:55 PM

I would get few high CFM computer fans and mount them in the trunk on the exhaust flap (not sure that is what it is called). You should see what I'm talking about if you remove the carpet by the rear light it is a little box with a rubber flap that you can push open.

By powering the fans and pushing air out of that location it will draw air from inside the car keeping it cooler especially if you leave the HVAC vents open (not set to recirculate). Some one did this on cleanmpg a few years ago.

Cobb · 05-08-2013, 05:17 PM

You mean something like this? http://99mpg.com/mima/people/lindahsolarvent/

NoD~ · 05-08-2013, 07:52 PM

Similar, but I really want to try and tap into the factory cooling fan. It will simply move more air than those PC fans will. The PC fans would be easier, sure, but not as effective.

I took my panel today and took a spare squirlcage motor and hooked it up. It spun at a pretty good pace! Without it being actually attached, it's hard to say how much air it will actually move, but guessing low-mid in comparison to the knob on the car's controller.

If all that fails, a pair of 140mm fans will fit where 6x9 speakers once were (my trunk isn't sealed up well enough to warrant using the exhaust flaps)... but I'd really like to get it working with the fan that's already there and proven to push some air.

Cobb · 05-08-2013, 07:55 PM

The PC fans are typically brushless where the blower isnt.

NoD~ · 05-08-2013, 10:13 PM

I know I see that listed all the time, and I have an idea of what that means... but what is the significance of that statement in relation to my goal here?

Cobb · 05-08-2013, 10:42 PM

They are more energy efficient and the bearings are made for continuous use. Blowers suck amps like most starters do and to vary the speed by dumping the current through a resistor.

I purchased these solar things you jam in the windows on my car. I tried parking in the shade. Basically when it gets over 100 degrees or the humidity is over 90% your best bet is to park with your ac on full blast. Then when you come back to your car reach in and start it up and stand beside your car reading your txts and such while the hvac blows out a majority of the hot air before you drive off.

Id use your solar rig to trickle charger your starter battery instead.

markweatherill · 05-09-2013, 02:49 AM

I have a feeling that running the car's blower while parked up with, presumably, the windows closed will circulate the hot air around and around the inside of the car, but may not achieve much real cooling.

Flakbadger · 05-09-2013, 03:57 AM

Quote:

Originally Posted by NoD~

Similar, but I really want to try and tap into the factory cooling fan. It will simply move more air than those PC fans will. The PC fans would be easier, sure, but not as effective.

I dunno man, there are some hellacious PC fans that move almost as much as an electric leaf blower. My computer has several 120mm fans that push well over 70 CFM... and they are somewhat conservative. There are many much more powerful ones out there. Might be something to consider anyway. Either way, cheers.

NoD~ · 05-09-2013, 08:44 AM

Hmmm, didn't realize brushess were more efficient... Think it is possible to convert the cabin fan into a brushless? Are newer cars brushless?

As for pushing around hot air, if you have the vent open to the outside air, you should be replacing the hot air building up inside with whatever temp air from the outside. If I leave my key on and let the air circulate for a few minutes before jumping in, it's a huge difference!

Edit: I'm thinking I will just go with the PC fan route... seems easier to design. Will just simply wire it up to the full 12v system and use a circuit design that kicks them on at ~90*F+, car on or off. Seems that a pair of fans in the rear 6x9 spots won't even draw a full amp of power, where the sunroof should produce 2-5 amps in that same sunlight that would be causing the heat in the cab anyways. Thanks for your help, gang.