Show HN: I built a 4000 watt solar array on top of my Tesla (AMA) | Hacker News Reader

Show HN: I built a 4000 watt solar array on top of my Tesla (AMA)

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25 pointssomid319 comments

Have you considered bifacial panels to get sunlight reflecting off the pavement? Depending on albedo it's perhaps (up to) 20% more power, but the panels weigh the same.

For direct DC-DC charging you'll need to convince the car that it's connected to a Supercharger (or CCS1 via the adapter), causing the vehicle to throw the internal switch and directly connect the charge port to the battery. This is followed by continuous communication so the car won't throw a fault and disconnect.

https://github.com/uhi22/pyPLC

https://www.heliox-energy.com/blog/dc-charging-a-complete-gu...

https://openecu.com/case_study/interface-evse-with-combined-...

Am I missing something or are there no pictures of the 4000W version, only the 2000W version? The 2000W version's panels encompass the entire footprint of the vehicle so I'm trying to imagine how on Earth you could possibly double the wattage still.

You're correct. My first build was with wood (TERRIBLE idea). Wood is too weak and it weights a lot. The 440 watt panels wouldn't work, it would break. The carbon fiber telescopic tubes also broke.

Beta2 is made with 3d printed parts, carbon fiber, and aluminum. I also have to keep EVERYTHING (including the roof rack and panels) less than 165. So the 4000 watt version is being built now. The 200 watt panels are about 30x60 inches, the 440 watt ones are 47x82 inches -- so it still fits on the roof. However when the 9 panels are opened the overall device goes outside of the shadow of the car.

The 4000 watt model is as if you opened your doors... it would extend that far.

I do a lot with solar for work, and had a few questions immediately. Are the Renology panels what you had access to chosen for a specific purpose? Some of the panels we use for high efficiency jobs are 400+ watts at a size closer to your 200w panels than your 440w panels. Also, have you considered using any type of optimizer or per-panel MPPT? Those can have a significant impact on real-world performance in my experience, especially in cases of shading or uneven panel soiling. With high efficiency panels, panel optimizers, and series stringing you could likely get to DC charging voltages (although at paltry amperage).

MPPT will cause more shading, but if the gains outweigh the losses, cool (and with only 9 panels calculating that shading will be pretty fast). My first thought was that making each panel articulate is a tough engineering problem when weight is a concern (but with smaller/more efficient panels like you suggest maybe it evens out on weight.).

So what are the panels in terms of weight, efficiency, composition?

Did you research any options for lighter weight or better efficiency panels? Are there any multijunction out there yet?

I wonder if a chinese fan design would be useful.

If they covered the entire car with flex panels I'd expect a similar result, right? If it gets 20 to 60 miles a day that would seem to be proof that solar cars could be A Thing and people in certain places could probably meet almost all their needs with just panels.

Really cool project!

I wonder if this kind of panel setup could be a trailer or hitch assembly that could be pulled. Maybe it has a battery on it too for charging on the go to get out to further places.

I bought a 400 and a 100 watt suit case panel for my not yet purchased lightning/cybertruck. They just charge my fridge and tent a/c battery at the moment.

Personally, I'll take the more utilitarian angle and get the lightning. I love Teslas but I love that the F150 has an onboard inverter to power your tools and can power your home if you have the correct charger/inverter

The cybertruck does both those things too.

11.5kw through the charge port, 9.6kw through the outlets (120/240v).

Amazing! Have you thought of commercializing this? In the long term as prices come down there’s no reason everyone shouldn’t have this.

Not as ugly as I thought it would be!

With some refinement and contouring to the body of the vehicle, this could make for a fully-untethered city taxi.

Assuming a taxi is driving most of the time, there just isn't enough possible energy to extract from the sun in that small of an area to sustain the workload.

How long would it take to charge the car? I asked ChatGPT4 and got this answer:

It would take approximately 2.5 days to fully charge a Tesla Model 3, which has a 50 kWh battery, using a 4,000-watt solar panel array under optimal conditions (assuming the solar panels operate at their maximum output for 5 hours per day). Keep in mind this is a theoretical estimate and real-world factors could affect the actual charging time.

Sure, that’s about right. 60 miles a day was a bit conservative. GPT thinks you can get 100 miles per day.

A small solar panel should be integrated into vehicles just to maintain the low voltage battery.

If anyone has questions, drop here. If you know about DC charging an EV message me

Might as well do away with the glass roof though

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