solar powered secondary AC system for keeping cabin and battery temps down

darknd666 · Apr 21, 2026

ChapmanF said: ↑

Right. Maybe I should have said it louder in post #3, but the factory solar roof option used the panel to run the HVAC blower under the dash. So it pushed fresh air into the cabin. The air, therefore, necessarily exited through the battery and the rear quarter vents.

So the difference between blowers, brushless for the solar option, or conventional with brushes otherwise, is a difference between HVAC blowers under the dash, not between battery blowers.

I don't know anything about where Nissens brand gets their ideas.

The difference that Toyota documents between the two blower variants is just that the brushless variant has a longer service life, so it can run all those extra hours when you're not in the car. The wiring diagram doesn't show any difference in fuse rating (a 50-amp fuse is used in both variants).

It certainly isn't there to be a more powerful blower and blow harder. Remember that the panel in the solar-vent gen 3 is rated 60 watts—in best conditions, unobstructed sun straight above the car, optimal temperature. At 12 volts, that's 5 amps, max.

And they want the system to still move some air even in partial, morning, or afternoon sun. So the design objective is a blower that spins easily and efficiently enough that even at quite low power input it can usefully move some air. It will never be spinning at those higher input power levels except when the car is on and you're using HVAC and the car electrical system is powering it.

As a little testament to how well the thing works at low input power, I modded my car to share power from the 60-watt panel to also charge the aux battery, and even after that, I still notice decent ventilation on sunny days.

On days with less sun, you hear the blower running intermittently. It seems the "solar battery air conditioning blower vent ECU" contains some kind of storage element, maybe some capacitors. If the solar input isn't enough to run the blower continuously, the ECU will bank up some power, run the blower several seconds, and repeat.
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The only nuance with this is that it's not a factory setup for the V so I would have to manually put the recirculate mode vent off assuming it stays in that position for the air diverter so that way it pulls fresh air from outside. Id really like to see where the wiring goes for the toyota solar vent control box. If I get down the rabbit hole far enough I will dig up the wiring diagrams on here, gonna try a simpler approach first.

darknd666 · Apr 21, 2026

ChapmanF said: ↑

As a little testament to how well the thing works at low input power, I modded my car to share power from the 60-watt panel to also charge the aux battery, and even after that, I still notice decent ventilation on sunny days.
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This should lower the power requirements by a lot as I priced out a 200W panel. I could probably get away with a 100W and use ot to keep the 12V battery topped off with a LVD switch like I mentioned earlier.

darknd666 · Apr 21, 2026

You know I wish I could fabricate a panel on the rear spoiler...that would be a great spot for it.

darknd666 · Apr 21, 2026

I think going with simplicity and more options for.panels I can just get a foldable for the dash and face the sun. The cramic coat on the windshield will undoubtedly reduce the panels effectiveness but a large foldout panel should still work.

Dan H · May 14, 2026

I too have recently thought about doing this as the summer temps are already here. Good tints are a must, and so are sunshades. I went with 3m crystalline all around(50% on windshield and 30% everywhere else). Made it too dark at night so that caused me to upgrade halogen headlights to leds. And I have a full tightly fitting windshield sunshade and I also opted to go for the white paint cause it keeps the interior noticeably cooler than other colors. But still, a 90°+ full sun day heats up the inside quite a bit. There has been a bunch of mini 12 and 24 volt compressor portable air conditioners hitting the market. So that got me thinking that 200W~300W of solar on the roof and a 100Ah battery could power one of these on low and maybe make a dent in the heat. It would help with the whole cabin and not just the HV battery. Though would need to find a way to vent it to the outside. Question about the brushless HVAC fan. Anyone ever figure out the amp draw when the vehicle was running compared to the brushed? Aren't brushless DCs supposed to be significantly more efficient?

darknd666 · Jul 10, 2026 at 8:28 AM

I just did ceramic tint on the windshield, 50%. 35% on the front windows, I wanna say I have 20-15% on the rear. Huge difference, Life changing. I also have a custom fit sunshade for the windshield, not only it has a reflective side but it also has thick foam board it feels like. The current weather conditions will be a real test as the next step is to insulate the roof with sound deadening foil faced closed cell foam. I may not need it but the cost will be way less than the tint job. The material im looking at now is 594mil thickness, it does have foil as I just mentioned. The tint alone has made the AC more efficient, i have a thick blanket I lay in the trunk area, im not 100% convinced it is the reason my battery has been performing better? Maybe insulating it fron the residual cabin heat? I mean the tint alone is what caused that reduction. I need to make these changes slowly with tests in between, to understand what changes made the most efficiency.

Im not really looking forward to stripping the interior for the insulation install.

solar powered secondary AC system for keeping cabin and battery temps down

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solar powered secondary AC system for keeping cabin and battery temps down

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