Hooking up a solar charge controller and inverter - Page 3 - Escape Trailer Owners Community

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Old 08-15-2015, 02:56 PM   #21
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Originally Posted by Daubsy View Post
Interesting. So a shunt is not needed for incoming amps from the PV?
No, the current from the panels goes through the controller, so the controller doesn't need a separately mounted shunt to measure it. To monitor a battery fully, all of the current going in or out of the battery need to be measured, so the shunt is mounted at the battery. It's safer and easier to do that on the negative ("ground") side as shown in the diagram than on the positive ("live") side.

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Originally Posted by Daubsy View Post
Does "cumulative amp hours" refer to battery capacity?
It could in other contexts, but in this case it is likely just referring to the accumulated output from the panels.
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Old 08-15-2015, 03:18 PM   #22
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Originally Posted by jxoco View Post
The PVGFP thing is a lightning protector(photo voltaic ground fault protector). I don't know if you would expect to need one of these with a trailer mounted solar cell. You would need one if the solar cell was mounted on the roof of a house.
I agree that is unlikely to be needed, but I believe that it is for - as it says - ground fault protection... not lightning protection.

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Originally Posted by fudge_brownie View Post
The Photovoltaic Ground Fault Protection Assembly is designed to minimize the possibility of fire resulting from ground faults. I am not familar with this product from Xantrex, the maker of your controller. A more common design is to have some type of circuit protection (fuse or breaker) between the panel and the controller and again between the controller and battery. I have used an automotive style breaker.
An automotive (or other basic) circuit breaker protects only from overload - excessive current. The ground fault system has essentially the same function as a GFCI (ground fault circuit interrupter), which detects any current going through the protective ground connection (rather than the wires intended to carry the current) and shuts off the power; that's quite different.

I didn't find anything from Xantrex of this type either, but Morningstar has a good description of their product of this type: GROUND FAULT PROTECTION DEVICE

It makes sense to me, but I had never heard of one before. I'm not expert in this area, but I don't see a high ground fault hazard for a panel on a trailer (especially if the panel frame is connected to one side of the panel's output circuit), and I don't see a big hazard in nominally a 12 volt (which means up to about 20 volts in some conditions) small solar power system. I think again this is part of some systems but not needed in this case.

Note that Xantrex has been purchased by Schneider, so this is now a Schneider Electric Solar C35. Here's the owner's manual
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Old 08-15-2015, 09:35 PM   #23
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Originally Posted by Brian B-P View Post
I didn't find anything from Xantrex of this type either, but Morningstar has a good description of their product of this type: GROUND FAULT PROTECTION DEVICE

It makes sense to me, but I had never heard of one before. I'm not expert in this area, but I don't see a high ground fault hazard for a panel on a trailer (especially if the panel frame is connected to one side of the panel's output circuit), and I don't see a big hazard in nominally a 12 volt (which means up to about 20 volts in some conditions) small solar power system. I think again this is part of some systems but not needed in this case.
I've never seen anythinglike it in a 12v system. But is does make sense for the much higher voltage systems.
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Old 08-15-2015, 11:32 PM   #24
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Originally Posted by Daubsy View Post
Interesting. So a shunt is not needed for incoming amps from the PV? Does "cumulative amp hours" refer to battery capacity?
Thinking out loud - as opposed to knowing all the facts - I would tend to agree with others that are saying a shunt is not needed for charging amps, and that "cumulative amp hours" is only measuring incoming amp hours.

My reasoning: The charge controller probably has no idea how big the batteries are, so it can't tell the user how many amp hours remain in the battery at any given time.

However, a number of popular battery monitors (Trimetric has been mentioned) are designed to measure both the incoming and outgoing amps and they will know the battery size because you tell it. Those will require a shunt in the location indicated in the diagram. Unfortunately you can't just go out and buy a shunt at random. It has to be matched to the device in question, so while the advice to buy a 500 amp shunt may be correct for one brand, it may not work correctly with another brand.

A bit of information for anyone who doesn't know how the shunt works: It is a well calibrated, very small resistance, mounted in a big chunk of metal, designed to handle hundreds of amps without causing more than a tiny voltage drop. This small voltage drop is what the monitor measures and converts the number to Amps using the equation Voltage = Current X Resistance.

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