Do I need to Ground my Solars Panels on My Canned Ham Camper

[MisterCookEMann]

I have 400 watts in Solar Panels installed on the roof of my canned ham camper that I am building. I have been watching Prowse's videos, and I have not seen him mention grounding the panels for his systems. But I have seen some videos of other people grounding their panels. My panels are not in contact with the trailer skin because I used petty tape between the brackets to ensure no leaking, but I could easily add a ground and connect, or maybe they are already grounded just from the bolts going through the skin? Anyways, I'm confused. Can Someone help me?

The set up I went with are solar panels charge Bluetti AC200, then that feeds my 12 volt trailer system in the trailer as well (which is very minimal, lights, fan, maybe a cooler at some point. That's it.

 

[Hedges]

If panels are connected in a series string exceeding 50 Voc, then they can present a shock hazard, if a wire rubs through or glass cracks and gets wet, electrifying the frame.
So I would say electrically bond frames and mounting hardware to chassis if (significantly?) above 50V.
Mounting hardware is generally not considered a good electrical connection - anodized, corroded, and the like, so special hardware is used.

Some DC charge controllers for batteries have PV strings 100V to 250Voc, which would be hazardous.
Many of us with grid tie operate up towards 600V
If you've got 12V or 24V nominal panels/strings then not an issue.

 

[MisterCookEMann]

If panels are connected in a series string exceeding 50 Voc, then they can present a shock hazard, if a wire rubs through or glass cracks and gets wet, electrifying the frame.
So I would say electrically bond frames and mounting hardware to chassis if (significantly?) above 50V.
Mounting hardware is generally not considered a good electrical connection - anodized, corroded, and the like, so special hardware is used.

Some DC charge controllers for batteries have PV strings 100V to 250Voc, which would be hazardous.
Many of us with grid tie operate up towards 600V
If you've got 12V or 24V nominal panels/strings then not an issue.

I have four 12volt 100 watt panels with a 24.6 voc, and I wired them in series, so that makes them over 50 voc right? Also for grounding the panels, I should connect each of the frames with a ground? Or since they are all connected to each other anyways, just connect one?

 

[Hedges]

All in series would be about 100V, could certainly be dangerous.
You must be using an MPPT charge controller, then.

Frames mechanically mount with some kind of screw clamping them to a rail, but the anodized finish doesn't make much if any electrical contact.
Here's one way to attach a lug that a copper wire can go in, one per panel.

GBL4 DBT Solar Module Grounding Lug Kit

GBL4 DBT Solar Module Grounding Lug Kit

www.solar-electric.com

 

[MisterCookEMann]

The panels will just be plugged into the new Bluetti Ac200 Solar Power Station, which is 35-150 voc. But what i'm confused about now is shouldn't the power station be grounded somehow?

 

[Hedges]

Those things generally don't get grounded, nor do portable generators.
AC power is a hazard, especially if you get wet (or it gets went). If kept dry, not much different from outlets inside your house.
We use GFCI outlets in kitchen, bath, and outdoors.
I don't find reference to either grounding or GFCI on the Bluetti.
It's just one of those things with risks, and you have to use judgement on how to use it safely.

 

[Zil]

I have 4 x 100W solar panels connected parallel. My charge controller has a case lug. It connects to a negative buss bar that then connects to the van chassis. I do not worry or care if the panel frames connect with a special wire to the chassis. It simply doesn't matter on a vehicle with such a small system.

 

[RCinFLA]

Short answer is yes, panel frames should be grounded. Since PV frames are usually aluminum you should use stainless steel hardware to reduce galvanic corrosion. Also good to put put a stainless washer between wire lug and frame. There are WEEB washers that have bumped/knurled surfaces to bite through aluminum oxide for a good connection.

Link to a good video on topic:

Back in the days when cars had chromed bumpers, I was changing out my car 12v battery on a hot Florida summer day, sweating alot. Wearing shorts, my thigh was pressed against bumper. As I started to unbolt the positive battery terminal, after a couple of seconds I felt a sensation like fire ants were bitting into my thigh. I learned why it was a good idea to disconnect the battery negative terminal first.

 

[Hedges]

I have 4 x 100W solar panels connected parallel. My charge controller has a case lug. It connects to a negative buss bar that then connects to the van chassis. I do not worry or care if the panel frames connect with a special wire to the chassis. It simply doesn't matter on a vehicle with such a small system.

Parallel, so probably no more than 25Voc, not a shock hazard.
Same panels wired in series like MisterCookEMann's system, and it would be enough to cook a man.
We try to implement protection at level of "do no harm" rather than at the threshold of injury. For instance, AC GFIC must trip no higher than 5 mA even though 30 mA could be the the level to cause cardiac arrest and 10 mA inability to let go. I don't immediately find the thresholds for DC.

 

[Zil]

Well that is a different question. But I would not worry about the aluminum frames. A short in one panel to its aluminum frame would bring down the whole system. Pay closer attention to the positive cables you lead into the trailer. It is foolish to wire 4 panels in series on a 12 volt system. Shading one part of one panel will drag the whole system down.

 

[Hedges]

Only if the aluminum frame has a low impedance electrical return path. If a human is the only return path, that's not low enough impedance.

Series connection of panels, especially as a single string, means shading of part of one panel lets current through its bypass diode, so power from all other panels and the other half of the partially shaded panel are still available. (Assuming quality/design so bypass diodes don't fail.)

Parallel connection, partial shading means not just half but all of that panel stops producing, because it's operating voltage is far below the others. (It'll probably reach Voc around the Vmp of the others, but no current.)

His Bluetti wants 35 to 150V, so if 12V nominal panels, needs at least 2S to work.
Depending on which panel (I'm used to seeing 17Vmp for some), on a hot day Vmp of two in series would drop below 35V reducing production.
So I think 4S1P is ideal.

 

[Forbisher]

His Bluetti wants 35 to 150V, so if 12V nominal panels, needs at least 2S to work.
Depending on which panel (I'm used to seeing 17Vmp for some), on a hot day Vmp of two in series would drop below 35V reducing production.
So I think 4S1P is ideal.

On the Bluetti 200 150V max is Voc so doesn't that imply that 35V min is also Voc and not Vmp?
I also read that minimum voltage to charge has been tested as less than 35V

 

[Hedges]

Max voltage would be Voc on a cold day with bright direct sun plus sun reflecting off clouds. Highest. Voltage. Ever.

Min voltage would be the lowest input at which it charges battery, so Vmp on a hot day with sun at an angle. But if it does say it will charge below 35V, then 35V isn't the minimum.

Some specs will give a voltage to start, and a lower minimum MPPT voltage.
e.g. this link for a string inverter:

https://files.sma.de/downloads/SBxx-US-DS-en-38.pdf?_ga=2.76114076.822230518.1603033128-621369231.1589916091

Rated MPP voltage range 155 - 480 V
MPPT operating voltage range 100 – 550 V
Min. DC voltage / start voltage 100 V / 125 V

Of course, those specs are from a company with decades of experience. Harder to divine limits of performance from Bluetti.
But with 35V to 150V range, just aim for the middle. About 100Voc from panel string at nominal 25C sounds good.

 

[MisterCookEMann]

Only if the aluminum frame has a low impedance electrical return path. If a human is the only return path, that's not low enough impedance.

Series connection of panels, especially as a single string, means shading of part of one panel lets current through its bypass diode, so power from all other panels and the other half of the partially shaded panel are still available. (Assuming quality/design so bypass diodes don't fail.)

Parallel connection, partial shading means not just half but all of that panel stops producing, because it's operating voltage is far below the others. (It'll probably reach Voc around the Vmp of the others, but no current.)

His Bluetti wants 35 to 150V, so if 12V nominal panels, needs at least 2S to work.
Depending on which panel (I'm used to seeing 17Vmp for some), on a hot day Vmp of two in series would drop below 35V reducing production.
So I think 4S1P is ideal.

Thanks for these great responses.

 

[MisterCookEMann]

All in series would be about 100V, could certainly be dangerous.
You must be using an MPPT charge controller, then.

Frames mechanically mount with some kind of screw clamping them to a rail, but the anodized finish doesn't make much if any electrical contact.
Here's one way to attach a lug that a copper wire can go in, one per panel.

GBL4 DBT Solar Module Grounding Lug Kit

GBL4 DBT Solar Module Grounding Lug Kit

www.solar-electric.com

So my plan for grounding is to get these clips and connect a copper cable, and ground it to the aluminum skin of the trailer. The aluminum skin is already grounded to the frame. Or, would it be better to directly ground the panels to the trailer frame. I would prefer grounding to the skin so I don't have to feed another wire through the ceiling. I used an entry box that only takes two wires, but it might be fine running the ground along one of those two wires without it ruining the seal?