Solar cannonball run

[stienman]

Jim Cleaver is starting his attempt at a cross-country trip in an electric vehicle solely powered by solar panels he's carrying.

Looks like a tesla, Sol-Ark, SOK 5kwh battery, and 64 100w flexible panels.

Here's his first video:

And here's a technical overview of the system hosted by Munro Live:

He plans to charge for two days and drive for one, about 300 miles each segment, so an average of 100 miles a day on a 6.4kW solar system. The panels will be four strings of 16, so shading (particularly since they'll be ground mounted - one edge lifted so they'll be angled) is going to be a big factor, I suspect.

On a sunny day it'll be mostly hands off, but given that the battery is smaller than the array, a highly variable day will probably require micromanagement - telling the car to stop charging, waiting for the battery to fill, telling it to start, etc. If the charge rate of the car is easily and finely adjustable - particularly if it can be done remotely - then maybe he can just tweak that every hour based on the battery level and array output.

It makes me wonder what the DC charging protocol looks like, and whether it would allow a low current DC "fast charge", so you could have a 400V output MPPT running off, perhaps, a 600V solar array directly charging the vehicle battery.

 

[Crowz]

Looking forward to following this one.

 

[chrisski]

I wonder if this has ever been accomplished a solar powered cross country trip before.

It makes me wonder what the DC charging protocol looks like, and whether it would allow a low current DC "fast charge", so you could have a 400V output MPPT running off, perhaps, a 600V solar array directly charging the vehicle battery.

Short answer is no. The battery is not directly accessible as you say without going through a level 3 protocol. More than just hooking the positive lead to positive and negative to the negative.

I can’t find them now, but I have seen home Level 3 DC Fast Chargers for sale in the neighborhood of $25k. There’s more to it than just putting a bunch of solar cells in series and tamping down the voltage to 400 volts charge.

 

[stienman]

The technical standards are available. My question was more about whether a tesla would accept a charge from a low current DC source, assuming that all the protocol and other connector/communication requirements were met.

It's still a 6kw DC solar array, so at 400VDC it would be about 16 amps, and I'm sure the car goes that low. But if the sun wanes, will the car disconnect if the charge is slower than 4kw or 2kw or 500w?

Obviously the charge station will have to communicate the changes continuously, but this is nothing new - tesla superchargers are configured two vehicles per supercharger controller, so if you plug one vehicle in you get the full output, but if another vehicle comes along and plugs in it reduces your charge by 50% and gives the other 50% to the other vehicle.

So the chargers can dictate how much current they'll supply, and then adjust it dynamically while charging.

I'm just wondering if there's a lower bound. The IEC 61851-1 charging standard (which Tesla adheres to) indicates a minimum charging current of 6A, which is 3kW at 500V, but teslas can control their charging current as well, with some users reporting that on AC stations they can go as low at 700W.

Anyway, it's a tangential topic, and we don't need to discuss it further here. It would be a useful area of research, though, if we wanted to develop solar vehicle charging plants that don't have their own storage. By reducing or eliminating the DC conversion equipment and battery storage, such stations could become very, very cost effective, though limited by solar conditions and area.

 

[Crowz]

Well he's almost there. Just watched the updates.