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Old 02-12-2021, 07:59 PM   #1
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Charger/inverter (and more) advice wanted

Hi all,

I'm hoping I can ask a favor of the crowd. I'm "asking for a friend" (really!)

As you might imagine, I've already offered my own take on the situation (I'll offer it here later), but I told him that I'd post here to get some other perspectives for him w.r.t. how to proceed /and/ why.

I'd love it if y'all can be direct, educational -- and super careful to be gentle. He's already pulling his hair out quite a bit and I'd like to be able to show him the whole thread, without making it worse. (I know didn't even need to mention that to this crowd).

I know that "hire an experienced, ABYC qualified marine electrician" is always the best advice. But, let's assume DYI, for the moment. Or, if you prefer, reframe the question as to how you'd expect an experienced ABYC-qualified electrician would proceed, and what would be recommended, and why.

THANK YOU SO VERY MUCH!

So...here is the situation...

He bought his 1st "big boat", a sailboat (not a trawler, I know), spent a few months doing maintenance, and he and his girlfriend have now quit their jobs, and plan to depart in 2 weeks for two years of open water cruising.

He replaced the exiting house batteries with a pair of huge lithium batteries, and replaced the existing inverter-charger with a Renogy 3000W unit with a lithium program, upgrading the supply to it to 10ga and the supply breaker to 30A in the process. The original inverter-charger has been saved to be reinstalled as a charger for the AGM start battery, since it charges differently than the lithiums. The Renogy units are brand-new, purchased from Amazon, and returnable.

The installation process remains "in progress". I don't know where he is with upgrading the wiring on the output side of the inverter-charger. He has not yet DC-grounded the inverter-charger chassis. The Renogy DC-DC charger for the house bank is not yet installed. The old 120VAC inverter-charger, which was originally the primary inverter-charger, has not yet been reinstalled as a charger for the starter battery. The new solar system has not yet been installed.

Shore power comes into the main AC panel via a 30A breaker, then out to the inverter via the newly installed 30A breaker. The inverter's output comes back into a 15A outlet breaker that covers all outlets in the boat (there aren't many). I think the 15A breaker is destined to get a twin, dividing the outlets between them, but do not know. There is no common bar across the breakers.

The galley is a newly installed electric stovetop and "countertop oven" mounted into a gimbling unit.

He noticed that, while inverting, but not while on shore power, the "reverse polarity" light on his main panel illuminated and asked me to look. A quick look at the wiring showed it was color/location matched. A GFCI outlet successfully self-tested and reset. All connections were found dry and clean.

I wasn't interested in seeing the demonstration, but I was told that, if, while inverting, one stands barefoot and touches the panel, the reverse-polarity light glows brighter.

~120V was found H-N at an outlet. ~65v was found N-G at the outlet. ~65v was found H-G at the outlet. Similar measurements were found at the AC panel. The reverse polarity light on the panel was found to be a resistor+LED wired between neutral and ground.

I called Renogy for tech support, which was a very frustrating experience. They assured me that my measurements confirmed the unit was working correctly. Their 2nd level support did the same. They also assured me that the unit is fit for marine use.

The AC and DC panels were Blue Sea Systems, so I called their tech support and let him chat with them for a bit. They were, as they always are, beyond truly superb. I'll elaborate on that conversation later. But, they again proved they are worth every penny that one might ever pay them.

I didn't have my tools with me, so I wasn't able to put a scope on the output. I was just using his multimeter. But, from those measurements, I assume that the 120v output is generated by taking it across complementary H-G and N-G sine waves vs a H-N sine wave with a grounding conductor tied to neutral.

Additionally, I'd like to note that I found ~24vac between exposed metal on the DC and AC panels. Filtering the AC by setting the meter for DC, ~2vdc was found between the same.


What do y'all think?

THANKS AGAIN, SO VERY, VERY MUCH!
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Old 02-12-2021, 09:48 PM   #2
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I think you have multiple problems like a neutral ground issue along with an appliance that has been wired backwards. I chased something like this once for days until I found a household refrigerator with the compressor wired backwards from the factory.
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Old 02-13-2021, 12:04 AM   #3
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What was done with the green wire? When inverting, I believe it should be tied to the N wire at the inverter output. When not inverting, it should be tied through the to green shore power. Inverter/chargers with a built in transfer switch usually do this if wired correctly. With green floating, the polarity light and a few other things could look pretty strange.
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Old 02-13-2021, 12:15 AM   #4
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The inverter incorporates an internal relay that a that switches the output wires between inverting and noninverting modes.

All green wires are tied together at the main panel.

If all load breakers are closed, the measurements remain the same if measured at the output of the inverter.

Thanks, y'all!
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Old 02-13-2021, 04:31 AM   #5
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Wow. That had a lot of typos....let me try again :-)


The inverter incorporates an internal relay that switches the output wires between inverting and noninverting (shore power) modes.

All green wires are tied together at the main panel.

If all load breakers are off, the voltage measurements remain the same, except the hot wire is disconnected by the single-pole breaker, but can be measured at the breaker panel or inverter output.

Thanks, y'all!
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Old 02-13-2021, 06:51 AM   #6
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Question:
- How will batteries get recharged while underway?
- Are the outlets GFCI? Are the 110 outlets/breakers grounds tied to a common buss bar and that bar in turn wired to ground?
- Is vessel located near some good electrical help if needed?
- Taking off to where in two weeks?

GK, you're a good friend
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Old 02-13-2021, 09:38 AM   #7
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It sounds like you have a floating ground, where it should be bonded to neutral. That's why you have a large voltage between N-G and L-G.


You need to research how the inverter handles this, or expects it to be handled externally. As DDW pointed out, the neutral to ground bond is tricky on boats (or any mobile application) because it needs to be different when on shore power vs when on inverter (or generator).


When on shore power, there should be NO neutral to ground bond on the boat, and the boat's ground should be tied through to the shore power ground. The Neutral to ground bond is in the shore power system, and should not be duplicated on the boat.


Without shore power, you lose the neutral to ground bond from the shore power system, and now need to make the bond on the boat. Many inverters do this internally via a relay that makes/breaks the bond based on the detection of shore power.
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Old 02-13-2021, 09:47 AM   #8
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Underway, the plan is for the alternator to charge the start battery and, once full or near full, a Renogy DC-DC converter will activate and converts the voltage on the starter/alternator side to the right voltage over time to charge the lithium house batteries. In so doing, it lets the alternator charge the house batteries.

The outlet in the galley is GFCI. The others are not, but there are very few other outlets and they are not near water.

The outlets all wire back to three bus bars (H, N, and G) for the outlet circuit, which in turn wires back to the breaker panel. The hot connects to the back of the outlet breaker. The neutral and ground each go to the corresponding bus bar within the breaker panel.

At this moment in time, the vessel is at a marina in Clearwater, FL, near Tampa. There are good service providers in the area. In 2 weeks the vessel will leave the marina for a short stay at a local anchorage. I don't know how short the short stay will be. I think it was intended to be days to a week or two.

Once departing the local marina, they begin the open water adventure. I understand that the initial trip will be south along the gulf coast to the keys, then up the Atlantic coast to Stewart, FL or thereabout, and then off to the Bahamas. Then global travel from there.


Quote:
Originally Posted by sunchaser View Post
Question:
- How will batteries get recharged while underway?
- Are the outlets GFCI? Are the 110 outlets/breakers grounds tied to a common buss bar and that bar in turn wired to ground?
- Is vessel located near some good electrical help if needed?
- Taking off to where in two weeks?

GK, you're a good friend
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Old 02-28-2021, 07:09 PM   #9
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To close out the threads the Renogy was replaced with a Victron and all is well. No volts and no ohms N-G while inverting, 120VRMS H to either.

Not sure if the Renogy was defective or supposed to be like that, but their tech support claimed it was fine, so my neighbor sent it back.
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Old 03-03-2021, 03:46 AM   #10
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I just realized that I left off an intermediate update about the 62V thing. I did go back over with a scope and my own meter to see what was going on.

The Renogy did not produce a split phase wave form. It did produce a 120Vrms sine wave from hot to neutral. But what I expected to be a grounding conductor did not seem to be properly tied to neutral while inverting.

I have no idea if this was by design, defect, or configuration. But, I suspect design as when I called their tech support, they saw no problem with the symptoms.

As for the 62V seen between hit an neutral or ground, it couldn't support any measurable current. I think it was an artifact of capacitance between the long runs of parallel wire, where what otherwise would have been the grounding conductor was floating or maybe some internal capacitors for managing noise from loads.

In any case, as I mentioned earlier, it was reolacednwith a Victron that works correctly with no weirdness.
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