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"Grounding Basics" Not Basic Enough for Me :)

You will probably get 10 different opinions for every question you ask especially when it comes to grounding. My opinion is you should contact the manufacturer and let them know what you would like to use the inverter for.

As far as I know Jackery and others isolate the AC input and output so they do not require a ground. Similar to using a 1:1 isolation transformer but those are rather large and heavy.

I use a cheap Bestek 300 watt SW inverter with my two Valence batteries and it does not require grounding. I like the inverter you linked to and I can imagine why you chose it.

Thanks. Yes, I'm going to contact Morningstar. I asked the question here preparatory to the call. Your comment about isolation goes straight to the question of how good the analogy is to the Jackery, and is therefore very helpful.

Everything that I've read about the Morningstar inverter, which has been on the market for a long time, is positive. I had an unusual reason for my initial interest. I plan to use it while recording sound, and it appears to be one of the very few inverters - maybe the only one in its class - that uses a heat sink, rather than a fan, to dissipate heat. As anyone who has watched YouTube videos about inverters knows, microphones and fan noise are not a great mix :)
 
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I plan to speak with Morningstar after I receive the inverter tomorrow and have had a chance to familiarise myself with the inputs and outputs.

The person who made this video is using a SureSine mounted in a converted school bus. The video is about grounding. In a response to a question in comments, he talks about a discussion about grounding that he had with Morningstar. I don't assume that his précis of that discussion is accurate, but it's interesting. As noted, I'll be speaking with the company myself in the next few days.

I'm mostly interested in knowing whether the analogy to a Jackery fails, and if so, exactly where it fails (@Gazoo raises a possible failure point above), and whether there's an easy way to address that failure. I'm also interested in what the maker of this video says, in comments, about his discussion with Morningstar.

 
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you could grab hold of a pair of hot and ground wires and enjoy the tingle all day long
:p
I grew up in 220V country doing stage audio visual in school. We used to wire 100V to a metal tool on the ground, and start l"looking for it" and wait for some smart ass to "find" it and pick it up. It amused our adolescent minds.

220V AC - will "wake" you up - while 10V can kill you .... Isn't electricity FUN :)
 
I intend to speak with Morningstar next week. I've found the following recent videos helpful.

On October 3, 2020, the YouTube channel Lithium Solar published a video on making a portable power station. That is essentially what I'm doing, but with a less powerful battery and inverter. The comments include discussion about grounding, among other issues. Will Prowse participated in the discussions.

Building a 5.0kWh DIY Portable Power Cart Hand Truck, Start to Finish



On October 6th, the channel published a follow-up video in which it addresses some of the comments made about the first video:

Adding GFCI and Over-current Protection to the DIY Portable Power Cart




Re those videos, it's worth noting my SureSine inverter's built-in protections (from the Installation & Operation Manual):

Screenshot 2021-04-02 at 12.45.00 PM.jpg
 
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One difference between the portable power station described in the Lithium Solar video (post just above) and what I want to do is that I will not have an AC In. My SureSine inverter is not a battery charger. I have a Victron IP65 to charge my battery, and my battery won't be connected to my inverter during charging.
 
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Will Prowse has some interesting things to say about grounding, including about mobile use, in his new video. From 06:50:

Offgrid Solar Inverter Buyer's Guide for Beginners



He also recommends this video:

Grounding - Safety Fundamentals

 
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I would assume If you have an isolated battery with AC inverter it can be dangerous with no ground/earth wire. If there was an issue with a device you had plugged in and you touched something metal you could become the path to ground and suffer the consequences. Lets use something simple as an example. Say you have a rice cooker and the AC main wire somehow wore through and shorted to the metal chassis and you touched it. Your going to get a nasty shock or die if your skin is moist enough. This video is an easy way to visualize ground wires in general. Seems like a Jackery or any other isolated power system with high volttage would be a more dangerous system to use since there is no way to get to earth ground.
 
Seems like a Jackery or any other isolated power system with high volttage would be a more dangerous system to use since there is no way to get to earth ground.
It's my understanding, and I could be wrong, Jackery and others are using something similar to a 1:1 AC isolation transformer. It might be good to confirm with the manufacturer of these types of products.
 
Morningstar has provided me with the name of an engineer to discuss this with, and I'll probably write a post afterward.
 
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This is the e-mail that I sent to a Morningstar engineer this morning. I could have phoned him, but I decided that setting out the context and my questions in writing is more efficient. The webinar that I refer to in the e-mail is the subject of this post.

I have plans to use solar panels and one of your controllers at my summer home, and the webinar that [name omitted] and you gave on Thursday was very helpful. I want to thank you for offering to address a question about my new SureSine inverter, which I actually want to use for purposes unrelated to my solar plans.

Context
I purchased a SureSine to use mostly outdoors, and occasionally indoors, with a 40Ah/512Wh LiFePO4 battery. The idea is to use this combination as a portable, mobile source of power. Outdoors, I won't be using it in the rain, let alone during thunderstorms. I'll frequently use it outdoors to power a light while shooting video here in New York City, where doing something like driving a stake into the ground is not realistic.

I know that Jackery (https://www.jackery.com) and other makers of portable power stations with AC outlets don't call for their products to be grounded. I don't know whether they do something within their products to address grounding or whether it's seen as unnecessary. A Jackery can be connected to solar panels, but I have no current plans to connect my battery and SureSine to anything, including solar panels, other than to a device that I want to power.

My Two Questions
What, if anything, do I have to do to ground my SureSine inverter? If I should do something, what actual risk am I running if I don't?

Re the point raised in earlier posts about the possibility that Jackery power supplies contain isolation transformers...

As we all know, these days many devices can be used with both 115V and 240V AC. When I lived in France, I purchased a tube amplifier for music that requires 240V AC. I continue to use this amplifier in Canada and the United States with a step-up transformer. The transformer is neither small nor light. As far as I can see, the same is true of the isolation transformers that are used with oscilloscopes. As I understand it, an isolation transformer is the same thing as a step-up transformer, just rigged differently. Indeed, I've read that a step-up transformer is actually a type of isolation transformer. I'm curious about this idea, because it isn't obvious how such a transformer is consistent with the size and weight of Jackery power supplies, especially the smaller ones.

Anyway, I look forward to Morningstar's response to my e-mail, which mentions the possibility that there is something inside Jackery power supplies that makes grounding unnecessary.
 
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On the theory that pictures help to make discussions more concrete, this is the battery (40Ah 512Wh) that I intend to use with the SureSine inverter. Details about the wiring are in this post. The 6AWG/13.3mm² cables will be connected to the SureSine's set screw terminal blocks with insulated wire ferrules (12mm/0.47" pins).

I've used an in-line fuse holder instead of a bolt down holder because one of my objectives is to make this rig as portable and as mobile as possible. For the same reason, I don't want to use grounding devices if it can be avoided. As should be clear from my e-mail (just above) to Morningstar, they are not practical given how I plan to use the battery and inverter.


cable.jpeg
 
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I sent my e-mail (post #30) to Morningstar before they opened this morning, and I've already (10:00 a.m.) received a response. I'm impressed with how quickly Morningstar replied, with the recognition of practical realities and with the concreteness of the advice.

The response starts by saying that grounding is important and that in some cases lack of grounding can be hazardous. That said, it notes that portable power supplies, because they are portable, are difficult to ground, and that it is commonly unfeasible to drive in a ground rod at every location.

I will be using the battery and inverter as a "floating system" without reference to earth ground, and take precautions. In particular, I'll ensure that 120V AC equipment is in good working order, with no frayed electrical cords, etc. If possible, I'll also use what are known as double insulated appliances that do not require grounding. These have plugs with 2 prongs instead of 3.

The SureSine manual shows a bond wire between AC neutral and the ground lug on the SureSine. I will not be using this bond, which is only relevant to grounded systems.

I would not be surprised if Jackery power supplies are also floating systems and that the precautions above are applicable.
 
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Further to the above post, the change that I'm making to the standard SureSine wiring is shown in this post in another thread.
 
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I sent my e-mail (post #30) to Morningstar before they opened this morning, and I've already (10:00 a.m.) received a response. I'm impressed with how quickly Morningstar replied, with the recognition of practical realities and with the concreteness of the advice.

The response starts by saying that grounding is important and that in some cases lack of grounding can be hazardous. That said, it notes that portable power supplies, because they are portable, are difficult to ground, and that it is commonly unfeasible to drive in a ground rod at every location.

I will be using the battery and inverter as a "floating system" without reference to earth ground, and take precautions. In particular, I'll ensure that 120V AC equipment is in good working order, with no frayed electrical cords, etc. If possible, I'll also use what are known as double insulated appliances that do not require grounding. These have plugs with 2 prongs instead of 3.

The SureSine manual shows a bond wire between AC neutral and the ground lug on the SureSine. I will not be using this bond, which is only relevant to grounded systems.

I would not be surprised if Jackery power supplies are also floating systems and that the precautions above are applicable.

Portable power device with earth grounding jack...

 
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Portable power device with earth grounding jack...


Thanks, very interesting. He says, at 02:55, that this Pecron S1500 is the first portable power supply that he's seen with a jack to connect a stake in the ground. If the Pecron is representative, it would suggest that all of these portable power supplies are floating system.

The 6' copper stake that he mentions is not included :)
 
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The Pecron S1500 (two posts up) is currently the subject of an IndieGoGO campaign. As far as I can see, there is nothing on the campaign page about the jack for grounding. However, the page links to the YouTube video below. The video, at 02:44, says specifically that the three AC outlets are not grounded, but can be via the jack and a grounding rod. I had a look at two of Pecron's user manuals for existing products. As with Jackery power supplies, they say nothing about grounding.

 
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