Solar DC input for charging Cybertruck from trailer panels

[markvan]

I'm close to retirement and want to explore the whole of Australia in the Cybertruck towing a caravan covered in solar panels.
I would love it if I could take it slow and just cover the miles a day I can charge from the sun.
I heard figures of something like 20km a day using the Cybertruck's own solar collector, but if I have a larger array of panels on my caravan, maybe 8x 300W panels, use those direct with DC (no loss by inverter) to charge the Cybertruck. Will the Tesla have the ability to charge control from an external source?
I could also use the Cybertruck as the power source for the caravan's inverter for the fridge, lights, internet and kettle. No need for large batteries in the trailer is what I'm hoping to achieve.
Any thoughts or advice on this would be appreciated.

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[CyberCop]

I’m pretty sure a trailer will be available not only with solar panels but with a battery pack under the floor to provide longer distances and energy for camping.

 

[Skennada]

I'm close to retirement and want to explore the whole of Australia in the Cybertruck towing a caravan covered in solar panels.
I would love it if I could take it slow and just cover the miles a day I can charge from the sun.
I heard figures of something like 20km a day using the Cybertruck's own solar collector, but if I have a larger array of panels on my caravan, maybe 8x 300W panels, use those direct with DC (no loss by inverter) to charge the Cybertruck. Will Tesla have the ability to charge control from an external source?
I could also use the Cybertruck as the power source for the caravan's inverter for the fridge, lights, internet and kettle. No need for large batteries in the trailer is what I'm hoping to achieve.
Any thoughts or advice on this would be appreciated.

 

[Skennada]

@ajdelange (a member) is well versed in solar and its parameters. I imagine he will be able to provide? some guidance here.

 

[ajdelange]

I'm close to retirement and want to explore the whole of Australia in the Cybertruck towing a caravan covered in solar panels.
I would love it if I could take it slow and just cover the miles a day I can charge from the sun.
I heard figures of something like 20km a day using the Cybertruck's own solar collector, but if I have a larger array of panels on my caravan, maybe 8x 300W panels, use those direct with DC (no loss by inverter) to charge the Cybertruck. Will the Tesla have the ability to charge control from an external source?
I could also use the Cybertruck as the power source for the caravan's inverter for the fridge, lights, internet and kettle. No need for large batteries in the trailer is what I'm hoping to achieve.
Any thoughts or advice on this would be appreciated.

@ajdelange (a member) is well versed in solar and its parameters. I imagine he will be able to provide? some guidance here.

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 panels 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.

 

[CyberCop]

? OMG, I’m so confused ?
So glad we have brainiacs in this club so I can get my questions answered.
Just make the answers in pictures please.

 

[ajdelange]

I know this confuses a lot of people and that is, I think, because we no longer are required to think quantitatively - it's all done by some electronic device for us. I'm old enough to remember that the first thing the grocer did when you went to check out was grab the paper bag your order was going into and a stubby pencil.

With BEVs people seem to have a hard time getting the concept that a kWh is a unit of energy which will deliver a certain number of miles just as a gallon of gas will deliver a certain number of miles. Part of this is because we say that our ICE vehicle is rated at, say, 18 miles per gallon but instead of saying our BEV is rated at 2.5 miles per kWh we tend to say it is a 400 Wh/mi. vehicle not only turning the distance - energy ratio upside down but introducing the Wh(1 thousandth of a kWh).

 

[Skennada]

I know this confuses a lot of people and that is, I think, because we no longer are required to think quantitatively - it's all done by some electronic device for us. I'm old enough to remember that the first thing the grocer did when you went to check out was grab the paper bag your order was going into and a stubby pencil.

With BEVs people seem to have a hard time getting the concept that a kWh is a unit of energy which will deliver a certain number of miles just as a gallon of gas will deliver a certain number of miles. Part of this is because we say that our ICE vehicle is rated at, say, 18 miles per gallon but instead of saying our BEV is rated at 2.5 miles per kWh we tend to say it is a 400 Wh/mi. vehicle not only turning the distance - energy ratio upside down but introducing the Wh(1 thousandth of a kWh).

Thanks.
There is no doubt that taking a few minutes to read and re-read (ponder/ruminate), some of the details begin to fall in place. An exhaustive detailed explanation is by all means better than a shallow mumble-jumble.

Thanks again.

 

[ricinro]

An 8.5 x 20' trailer has about 15.8 meters^2 on its roof. by using well designed fold out brackets and a fanfold design you could make solar awnings on both sides of the trailer that extend some multiple of a solar panel width. (The dimensions of an average 400 Watt solar panel are about 79” X 39” X 1.4”.).

So for a 20' trailer you could stack 3 x 2 of these 4-6 panel fanfolds. Lets go crazy and assume you use a 6 panel fanfold. this would require awnings to support 5 of the panel widths from the side of the trailer (5 x39"- 195" or 16 feet). So 16 foot awnings on both sides of your trailer gives you 36 400w panels or 14400 watts.
after all the losses etc maybe you can go 4.5x farther than 8 panels (112kms). And you get a lot of shade!

 

[fritter63]

Perhaps a better solution would be to wire up the trailer with solar panels and micro inverters (enphase). One inviter per panel then and the output at the end of the wire is A/C. Then you could just plug it into a level 2 charger on the trailer, which is connected to the panels output?

The big issue is that inverters are wired to not produce output unless there is a load coming in as well (ie, power from the grid). This is done to ensure that if the power is out and they are working on the lines, you aren't a rogue power source energizing the lines! So maybe you could hook up a small battery (hint hint, power wall!) that would serve the purpose of storing your energy, powering up the line to enable the inverter output, and then you could charge from that?

Another question is how the level 2 charger would handle the varying output from the panels (ie, as the sun moves, etc).

 

[fritter63]

and I see that @ajdelange pretty much said the same in their last paragraph.

 

[ajdelange]

Perhaps a better solution would be to wire up the trailer with solar panels and micro inverters (enphase). One inviter per panel then and the output at the end of the wire is A/C. Then you could just plug it into a level 2 charger on the trailer, which is connected to the panels output?

The big issue is that inverters are wired to not produce output unless there is a load coming in as well (ie, power from the grid). This is done to ensure that if the power is out and they are working on the lines, you aren't a rogue power source energizing the lines! So maybe you could hook up a small battery (hint hint, power wall!) that would serve the purpose of storing your energy, powering up the line to enable the inverter output, and then you could charge from that?

You have just described a solar charging system for an off grid cabin or house. So why couldn't you do it on a trailer? Well you could of course but there is one little additional catch. The individual micro inverters are controlled by a board in a panel which contains the breakers for arrays of panels/microinverters. It think they call it the Envoy. This device is programmable only by Enphase certified installers - the owner has no control. And it requires an internet connection. I do not know if the system shuts down if the internet connection is lost.

Another question is how the level 2 charger would handle the varying output from the panels (ie, as the sun moves, etc).

The real beauty of a micro inverter system is that each micro inverter loads the panel to which it is connected at the level which extracts the most power possible given the incoming sun light level. Thus if a certain panel is shadowed by, say a tree branch, at a certain time of the day, that microinverter would only deliver, e.g., a quarter of an amp to the 240 V bus as opposed to the 1 ampere it is able to produce in full sun. Of course there are limits. When the sunlight level gets low enough the micro inverter shuts off. In any case the vehicle charger would be connected to the AC bus on which not only the microinverters sit but also the powerwall. Were a cloud to pass over the panels shutting them all down the load would be taken up by the PowerWall.

Enphase has been promising a new microinverter (the IQ-8 I think it is called) that can clock itself intended for use in off grid systems.

All said and done it is indeed conceptually possible to structure a charging "wagon" using the proposed architecture

 

[Youaregoldone]

I know this confuses a lot of people and that is, I think, because we no longer are required to think quantitatively - it's all done by some electronic device for us. I'm old enough to remember that the first thing the grocer did when you went to check out was grab the paper bag your order was going into and a stubby pencil.

With BEVs people seem to have a hard time getting the concept that a kWh is a unit of energy which will deliver a certain number of miles just as a gallon of gas will deliver a certain number of miles. Part of this is because we say that our ICE vehicle is rated at, say, 18 miles per gallon but instead of saying our BEV is rated at 2.5 miles per kWh we tend to say it is a 400 Wh/mi. vehicle not only turning the distance - energy ratio upside down but introducing the Wh(1 thousandth of a kWh).

Sorry, but l believe u are confusing this person even more with your simplified further explanation.

 

[ajdelange]

Unfortunately, you may be right. When I ponder the future of America the inability of the average man on the street to understand math this simple frightens me more than the idiots who think they can change history by knocking over a few statues and the imbeciles who won't wear a mask in the midst of an infectious disease pandemic.

 

[VolklKatana]

Just one thing to mention here that might throw a wrench into all of this...in the current Tesla's, you cannot move the vehicle when plugged in. Obviously this for fear of ripping a super charger out of the ground. So you would somehow need to get around that hurdle, which would be a software limitation on Tesla's side. Others have gone down the path of 'hacking" the software, but the cons almost always outweigh the pros when all things are considered.