Solar DC input for charging Cybertruck from trailer panels

[Sandybayes1]

Oh, er, sure. It all depends on how much energy it takes to go a km and how much energy you can collect from the sun. A CT is probably going to need about 450 Wh/mi = 279 Wh/km. The first issue of concern is that when you tow anything it imposes additional demands on the battery. It takes energy to move a caravan just as it takes energy to move the truck. The main factors in that demand are the weight and drag characteristics of the towed vehicle. Without actually towing the caravan in question it will be difficult to estimate its consumption but it is not unusual for it to be equal to that of the truck implying a doubling of consumption and halving of the range that one can go on a kWh.

Now let's look at your array. 8 X 300W = 2.4 kW DC. You cannot pass that directly to the battery becuase the cells are arrayed such that the panels produce a low voltage (10's of volts) and the battery in the vehicle is close to 400 V. DC/DC conversion is necessary. Maximum Power Point tracking, while it prevents a lot of lost energy when the sun gets off zenith, produces some loss as well. So realistically your 300 W panels may produce more like 250W and that, a quarter of a kW, makes the math easier. Each panel will produce that quarter kW when the insolation striking it is 1 kW/square meter (full sun). So the next question is how many equivalent hours of full sun will those panels receive in a day. I always used to joke that the easiest job in the world would be weather forecaster for 8HA: "Tomorrow the weather in the Alice will be fine. For the remainder of the week it will be fine". So let's assume 7 hours a day (I'd have to know where you are and the time of year to make a more accurate estimate). That's 7/4 kWh energy collected by each panel each day or 56/4 = 14 kWh per day for the set of 8. Assuming 2*279 = 559 Wh/km this energy would carry you 14000/559 = 25 km.

Another aspect to all this is as to whether one would be able to take on any charge from either the trucks integral panels or from panels on an attached caravan. At this time it is only safe to assume that the answer with respect to the latter is "no" so that one would have to use the batteries on the caravan to charge house batteries and that the energy from the house batteries would have to be inverted and used to charge the CT through its charging port when stopped.

I’m thinking that any technical issues are solvable and also this retired person is not going to be driving daily. You have to stop to see the sights you know, which is also time to recharge batteries. Even the trip into Alice has plenty worthy to stop and see! My concern would be around those areas where sun might not be as plentifull in the tropical or dense forest areas.

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[ajdelange]

I’m thinking that any technical issues are solvable and also this retired person is not going to be driving daily. You have to stop to see the sights you know, which is also time to recharge batteries. Even the trip into Alice has plenty worthy to stop and see!

Absolutely true but many of them are pretty far apart. Can you see going up "The Track" or out the Lassiter in 20 km chunks?

 

[Crissa]

Why would you have to stop every 20km?

You leave the truck at camp, charging, while you do your daily adventures on your Cyberquad, Zero Motorcycle, or Arcimoto FUV which would charge easily off your Cybertruck's battery pack. (And use up to a tenth of the per-mile power consumption)

Hopefully there will be a port for plugging in energy sources in the back so you can have extra battery packs or solar panels. It would be best if it didn't require an inverter, since the batteries and panels are DC. Inverters and chargers are heavy and bulky.

-Crissa

 

[ajdelange]

Why would you have to stop every 20km?

To charge. Actually 20 km is the number from the OP and represents an optimistic estimate of how much charge Elon Musk thinks solar cells built into the toneau could charge a CT.

In No. 5 I estimate an additional maximum of 25 miles from the additional panels OP thinks he might be able to carry on top of his Caravan.

You leave the truck at camp, charging, while you do your daily adventures on your Cyberquad, Zero Motorcycle, or Arcimoto FUV which would charge easily off your Cybertruck's battery pack. (And use up to a tenth of the per-mile power consumption)

Anything that sucks power from your CT battery pack deducts from the range you collect from the sun. With the supplemental panels he'd have 25 + 20 = 45 km (28 miles). From that he has to pay the phantom charging tax of 8 - 10 miles leaving 18 to 20 miles less whatever he gave away to the Cyberquad. I doubt you appreciate how desolate this part of the world is. Maybe he's a real Thoreau but moving up the Stuart at 20 miles per day just doesn't seem very practical.

Hopefully there will be a port for plugging in energy sources in the back so you can have extra battery packs or solar panels.

There is. The charging port.

It would be best if it didn't require an inverter, since the batteries and panels are DC. Inverters and chargers are heavy and bulky.

The battery is about 350 VDC and solar arrays produce perhaps 24. Thus a DC/DC converter is required and it has to match whatever array you buy to the truck's DC bus voltage. Panels installed as part of the truck would very probably have this. Anything external would require an additional interface which I very much doubt Tesla will supply though the application of unfolding and setting up some solar panels at a campsite will probably be something a lot of people will do and it is feasible. If Tesla does not furnish an external DC interface then you must have a buffer battery and inverter and use the charging port. Modern inverters are pretty light and efficient but batteries are not light.

 

[Crissa]

To charge. Actually 20 km...

That's per day for the built-in works-while-you're-driving panel on the tonneau cover. Solar from a trailer or fold-out solar would be far more extensive.

https://www.routedelsol.com/post/wait-you-did-what

What you can put on a trailer is huge.

And even if not more panels... Why would you be limited to the tonneau cover miles each day? Those miles are cumulative. You have a battery. Just camp/play longer until you have the miles stored up for the next hop.

The battery is about 350 VDC and solar arrays produce perhaps 24.

A) That's straight up wrong. Most panels are 48-72v.
B) You array solar cells just like batteries. The voltage is entirely based upon the install.
C) Efficient controllers already are doing DC-DC conversion or has microinverters to manage the fluctuation of voltage as sunlight waxes and wanes, and battery and load require more or less.
D) You can also array solar controllers to stack voltage or amperage, depending upon your need.

My camp install runs all my panels in series, which stacks all the voltage instead of in parallel. That's so the controller can still trickle charge no matter the amount of sunlight.

-Crissa

 

[ajdelange]

That's per day for the built-in works-while-you're-driving panel on the tonneau cover. Solar from a trailer or fold-out solar would be far more extensive.

What you can put on a trailer is huge.

My calculations are in #5. And expanded on in # 19 It helps if you read the other posts especially the one you are responding to. But my calculations are set out. Please share yours.

And even if not more panels... Why would you be limited to the tonneau cover miles each day?

If you were to read #19 you would learn that the OP doesn't want to travel with a huge trailer ("caravan" in the Australian term for trailer). He wants to use the caravan he has upon which he estimates he can install "maybe 8" panels. It is also helpful, in trying to make a meaningful contribution to a thread, to read all the posts. Especially the original one (OP).

Those miles are cumulative. You have a battery. Just camp/play longer until you have the miles stored up for the next hop.

Do you know what phantom/vampire drain is? If not, look it up. Do you know how vast Australia is? We have been using the example of the Stuart Highway here as it goes right up the centre of the country and has lots of fascinating things to see along it and at its ends. But it's 1879 miles from Adelaide to Darwin. I estimate, with the number of panels he wants to carry that he can "collect" energy for 20 miles per day if he is willing to keep his arrays aimed at the sun throughout the day and the sun shone all day every day. One of the reasons for picking "The Track" as an example is that except for a month or so ("The Wet") the sun does shine there all day every day. It would, thus, take him 94 days to collect enough energy to make this journey, Again, I would be pleased to look at your calculations.

A) That's straight up wrong. Most panels are 48-72v.

You will come across better if you check your facts before making a strong declaration of this sort. The panels in my home installation produce 33.5 volts at the peak power point at 1 kW/m^2 insolation. As they never get that (but some get close to it for a few minutes around apparent noon near the solstice) they will be operating at voltages somewhat lower than that most of the time. As I am writing this I am charging a battery pack with arrays that produce 18 V (presumably also at the PPP).

B) You array solar cells just like batteries. The voltage is entirely based upon the install.

My solar cells aren't at all like batteries. They are like current sources in parallel with a diode. The voltage produced depends on the way the individual cells are interconnected and on the load presented,

C) Efficient controllers already are doing DC-DC conversion or has microinverters to manage the fluctuation of voltage as sunlight waxes and wanes, and battery and load require more or less.

In the application under discussion in the most ideal architecture the vehicle would have a DC/DC converter with MPPT (Max Power Point Tracking) connected to MC4 (or other common) connector to raise the ~30 volts of the array to vehicle DC bus voltage (around 350 V). But as I explained in my previous post this would require additional interfacing software and hardware to interface to the vehicle. Besides convenience the vehicle battery does the buffering. Absent the direct interface one must have an external battery as a buffer, a controller to charge the battery at the MPP and an inverter allowing the battery to charge the vehicle through the Level 2 port.

 

[Crissa]

Do you know what phantom/vampire drain is?

It's simply things that use power all the time. Even solar controllers have a minimum power level they need to function to turn back on later.

They are like current sources in series with a diode. The voltage produced depends on the way the individual cells are interconnected and on the load presented,

...Which, regarding voltage, is just like batteries. The number of cells in an array parallel makes more current, the number in series makes more voltage. Wallah.

-Crissa

 

[ajdelange]

As a matter of general interest: If you seek to drive from Darwin to Adelaide on solar power the car you want is the Lightyear One which claims to be able to extract 12 km of range from an hour of full sun. With 6 hours effective full sun in a day that would get you 72 km.

The guys that are building this car are from the group that won the Darwin to Adelaide solar car competition a few years back. They have made the trip on sun energy alone.

 

[ajdelange]

It's simply things that use power all the time. Even solar controllers have a minimum power level they need to function to turn back on later.

It's good that you know what it is but I am more concerned that you understand that you must deduct it from what your arrays collect.

...Which, regarding voltage, is just like batteries. The number of cells in an array parallel makes more current, the number in series makes more voltage.

The current voltage curve of solar cell is not at all like that of a battery. They are different animals altogether. But it is true that if you series sources the voltage increases and if you parallel them the current does.

Wallah.

Well, OK. I guess I'm an "engineer wallah" but I've never been called that before. Are you from India?

 

[Crissa]

Well, OK. I guess I'm an "engineer wallah" but I've never been called that before. Are you from India?

https://en.wikipedia.org/wiki/Transylvania_6-5000_(1963_film)#Plot

I didn't mean to sound like I was making fun of you; being overly pedantic is a good feature in engineers. But when looking at possibilities, you need to ignore that trait to be creative. Poetry is just engineering of a different kind.

-Crissa

 

[ajdelange]

So this remark had something to do with the Walla Walla indians? That's not the kind of Indians that would refer to someone engaged in a particular profession a wallah. In any case, what has this to do with series/parallel connection of circuit elements?

 

[Crissa]

So this remark had something to do with the Walla Walla indians? That's not the kind of Indians that would refer to someone engaged in a particular profession a wallah. In any case, what has this to do with series/parallel connection of circuit elements?

Is this a joke?

-Crissa

 

[ajdelange]

That's what I am trying to find out. You use the word "wallah" in the post. That is a person who specialized in a particular endeavour: punk wallh, tonga wallah, engineer wallah... So, naturally, I ask if you are Indian.. You reply with a link to a Buggs Bunny cartoon in which he uses the invocation "Walla Walla Washington". That town is named after the Walla Walla indians. Thus I assume that you misunderstood when I said Indian (actually I asked if you were from India - not whether you are Indian. Then you want to know if I am joking? WTF? Over.

What I really want to know is what you meant when you put wallah in a post at the end of a sentence about series and paralleling solar panels. If it's a joke, I don't get it.

 

[Crissa]

That's what I am trying to find out.

https://www.lexico.com/grammar/exclamations

-Crissa

 

[Newton]

I read wallah as...

walla(h)
There it is; there you are. A misspelling and mispronunciation of the French "voilà," an exclamation calling attention to or expressing satisfaction with something that has just been presented or accomplished.