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Discussion Starter · #1 ·
I read way back that the solar roof puts out approximately 120 W on a sunny day. That's not a lot compared with the 30,000 W + consumption of our cars during acceleration, but it IS a lot of power if thoughtfully used. For example, most consumer cooling fans are around 10-15 W and do a great job moving hundreds of cubic feet of air per minute. 120 W if devoted to efficient cooling fans should create a tornado in the Karma's cabin. 120 W is enough to run two high-end laptop computers simultaneously, charge an impressive number of iDevices, etc.

So I've always been curious why the Karma appears to do so little with the 120 solar watts once the 12 V is charged. I appreciate that the circulation fans turn on, but why is the airflow from them so low? (I recall the experiment posted here recently that used streamers to confirm that the fans are in fact blowing). Why not use the 120 W to power the USB bus or cigarette lighter 12V port of the Karma so at least our devices can all charge courtesy of the sun? Or ramp up the fan speed so cabin cooling can be improved?

It's also possible that just to power on the controllers that control the fans, etc. takes up most of the 120 W, in which case my suggestion would be to revise the controllers :)
 

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drliu said:
...
So I've always been curious why the Karma appears to do so little with the 120 solar watts once the 12 V is charged. ...
That's 120 watts peak, which is to say, not actually 120 watts. ;)

Still, there might well be some things you could do with a more typical 50-to-75-ish watts...
 

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Putting solar panels on the roof of a car is mainly a cosmetic/marketing gimmick. As you've pointed out, the amount of power they provide is minuscule compared to the what's required to move a car. The only two functions of value are maintaining the 12V battery and blowing fresh air into the cabin. But as you've also pointed out, this can be achieved with a much smaller solar panel than what on the Karma.

For example, here's the panel on the Nissan Leaf that performs the same funtions:

(I'll point out that the Leaf also has proper cabin pre-conditioning that can be set via a timer or smartphone app.)

Anything larger than this is overkill. Solar panels are best placed on the roof of your house.
 

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Discussion Starter · #4 ·
Good comparison with the Nissan Leaf. Given the muuuuccchhh larger size of the Karma's solar roof, it should be possible to do more than very modestly cool the cabin on a hot sunny day, no? It would be good to know if Fisker is brainstorming more effective and creative uses of the solar roof as part of their promised fix to the solar screen. Perhaps for a future MY or upgrade, it would be awesome, for example, if the cup holders could be chilled with a peltier thermocooler; I think even a 10 W cooling element would keep a typical drink-size volume of liquid cool. But I'll just be happy if the impressive solar roof can keep my Garmin GPS charged in perpetuity!
 

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Discussion Starter · #7 ·
I disagree with the idea that a solar roof is as useless as a (non-functional) bracelet. A 100 W solar generator can be very useful-- it's just that I don't think Fisker (or Nissan, etc.) have yet discovered the best use of it. Heck, even allowing us to charge our devices by powering the 12V or USB bus would be more useful than the barely-there fan. Or how about increasing the airflow from the solar-driven fans? Charging low-power LED reading lights above each seat? Keeping the GPS synced 24/7? etc. etc.
 

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drliu said:
I disagree with the idea that a solar roof is as useless as a (non-functional) bracelet. A 100 W solar generator can be very useful-- it's just that I don't think Fisker (or Nissan, etc.) have yet discovered the best use of it. ... Or how about increasing the airflow from the solar-driven fans? Charging low-power LED reading lights above each seat?
Agree about increasing the airflow from the fans. Surprisingly, the interior reading and courtesy lights all use incandescent bulbs instead of LEDs, which makes zero sense considering Fisker's Eco Ethos. Once they start burning out, I will be replacing them with LED-based bulbs. But for now, they are working and there is no sense in creating waste.
 

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Fabulist said:
drliu said:
I disagree with the idea that a solar roof is as useless as a (non-functional) bracelet. A 100 W solar generator can be very useful-- it's just that I don't think Fisker (or Nissan, etc.) have yet discovered the best use of it. ... Or how about increasing the airflow from the solar-driven fans? Charging low-power LED reading lights above each seat?
Agree about increasing the airflow from the fans. Surprisingly, the interior reading and courtesy lights all use incandescent bulbs instead of LEDs, which makes zero sense considering Fisker's Eco Ethos. Once they start burning out, I will be replacing them with LED-based bulbs. But for now, they are working and there is no sense in creating waste.
I find that if I just crack the windows open a bit, the cabin is significantly cooler after the Karma has been sitting in the sun. It gives the hotttest air somewhere to go when then fans operate.
 

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BillyO,

For years I've been in the habit of cracking the windows open a bit in hot weather. The Karma has the "touchiest" window controls yet. It's very difficult to get the windows to stop just where you want them. So..... they remain shut.
 

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BillyO said:
Fabulist said:
drliu said:
I disagree with the idea that a solar roof is as useless as a (non-functional) bracelet. A 100 W solar generator can be very useful-- it's just that I don't think Fisker (or Nissan, etc.) have yet discovered the best use of it. ... Or how about increasing the airflow from the solar-driven fans? Charging low-power LED reading lights above each seat?
Agree about increasing the airflow from the fans. Surprisingly, the interior reading and courtesy lights all use incandescent bulbs instead of LEDs, which makes zero sense considering Fisker's Eco Ethos. Once they start burning out, I will be replacing them with LED-based bulbs. But for now, they are working and there is no sense in creating waste.
I find that if I just crack the windows open a bit, the cabin is significantly cooler after the Karma has been sitting in the sun. It gives the hotttest air somewhere to go when then fans operate.
good ole hand cranked window...don't you miss it.

Or can modern technology has a window setting for a (programmable) crack opening?
 

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Bert Yetman said:
BillyO,

For years I've been in the habit of cracking the windows open a bit in hot weather. The Karma has the "touchiest" window controls yet. It's very difficult to get the windows to stop just where you want them. So..... they remain shut.
You may already know this, but to stop a window part way in a Karma, you should not push the window button in the opposite direction of travel (which is the obvious thing to do) rather, you should press the button in the same direction again and the window will stop moving. So if you are opening a window, press the button down, then press it down again where you want it to stop. I think you will find that it is very easy to precisely stop a window anywhere in its travel using this trick.
 

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Umm, you could also try not to push so hard on the button as it is a 2 stage one. Push it lighly for manual adjustment, you should feel a small notch halfway. Pushing it all the way down activates the auto-down function.
 

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As far as I know, all cars with auto-down and auto-up features have a two-stage button. It is only logical.
 
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