Break Pos or Neg on Solar Panel wire to controller

[KP44]

Originally Posted by a64pilot

I believe the flow of electricity is from negative to positive, if so the Brits had it right with their old cars

Yes. The positive (active, seeking) pole is called "negative" and the negative pole (inert, void) is called "positive". Go figure.

[jbinbi]

Just found this online. Looks like a knockoff of busman products. good reviews, great price.

https://www.amazon.com/KUMEED-Circui...2Bbreaker&th=1

[OrangeCrush]

Originally Posted by jbinbi

For what I am trying to do, which is just to break the line from the panel to the controller, I have actually thought of just using a standard light switch from HD. I need to use this switch maybe a few x a year. I bet this would work fine for $0.99. I know it's not marine rated etc., but this is inside under the berth out of the way.

As I've been told, switching DC on and off is much harder on the switch itself because as the contact is made or broken, the electricity arcs over the gap and deteriorates the point of contact. A switch designed for AC systems probably won't last long on a DC system. But I'll leave it to the experts to tell you why not to spend a dollar on a cheap switch and use it until it breaks. Seems like a decent strategy to me, as long it did not create a risk of a short.

On my last boat I had various panels with backflow diodes hooked up to the same duplex cable that could be disconnected with a waterproof polarized plug. I only disconnected it once a year in the fall and reconnected it in the spring. The negative contact seemed to corrode rather quickly, but it was probably due to my old boat being poorly wired up in general. I'm obviously not an authority on this stuff, just sharing my experiences.

[buzzstar]

OK, I semi understand about grounds, having once had an MG TD Mk II with 6 volt positive ground, but it always has been my understanding and operating presumption, at least with DC, as produced by a generator, alternator, or a solar panel, that if the circuit was not complete there was no production, although depending upon the details, if you accidentally completed a circuit, you could be in for a shock, and it did not much matter which end you completed. Is this incorrect?

[Wotname]

Originally Posted by a64pilot

I used fuses, they open up to disconnect, actually I used a combiner box that has a lightning arrestor and fuses.
I believe the flow of electricity is from negative to positive, if so the Brits had it right with their old cars

Originally Posted by KP44

Yes. The positive (active, seeking) pole is called "negative" and the negative pole (inert, void) is called "positive". Go figure.

Well the electrons move from negative to positive terminals outside of the generating source while the holes left behind (where the electrons were) move from the other way (of course), i.e. positive to negative

Originally Posted by buzzstar

OK, I semi understand about grounds, having once had an MG TD Mk II with 6 volt positive ground, but it always has been my understanding and operating presumption, at least with DC, as produced by a generator, alternator, or a solar panel, that if the circuit was not complete there was no production, although depending upon the details, if you accidentally completed a circuit, you could be in for a shock, and it did not much matter which end you completed. Is this incorrect?

You are mostly correct. All electrical circuits require a circuit! That is, a complete path (loop) to and from the generating source whether that be a battery of an alternator or whatever. AC or DC, it's the same in so far you need a intact circuit. Hence when we say, it's an open circuit, we mean the circuit is no longer complete and electrical current stops flowing.

[ramblinrod]

Originally Posted by jbinbi

I would like to have my solar panels able to be turned off to the controller for any number of reasons. One main one is that my controller wants no V in when connecting/disconnecting to the battery. It is PITA to get to the little screws connecting the wires to the controller, so just wanting to do that means unconnecting the panels from the controller.

Having a switch/breaker would be much better. I purchase the blue seas breaker
https://www.bluesea.com/products/cat...ers/285-Series

Was planning on putting this on the POS wire from the panel to the controller. Then an electrical person at the yard said to break the NEG? I know about electron flow etc., but doesn't it make more sense to break the POS in this case.

Thanks

Just use MC4 connectors.

That's what they are for.

That way, you can isolate the panel if desired AND you can remove the panel easily (like for hurricane prep).

I've owned a solar charging system for 3 years and never once wished I had a breaker in the panel to controller connections.

For negative ground boats, it is common to "break" the positive connection.

[ramblinrod]

Originally Posted by jbinbi

I would like to have my solar panels able to be turned off to the controller for any number of reasons. One main one is that my controller wants no V in when connecting/disconnecting to the battery. It is PITA to get to the little screws connecting the wires to the controller, so just wanting to do that means unconnecting the panels from the controller.

Having a switch/breaker would be much better. I purchase the blue seas breaker
https://www.bluesea.com/products/cat...ers/285-Series

Was planning on putting this on the POS wire from the panel to the controller. Then an electrical person at the yard said to break the NEG? I know about electron flow etc., but doesn't it make more sense to break the POS in this case.

Thanks

Actually answering the question...

If the panel frame or charge controller input is grounded (negative per ABYC standards if grounded), place the switch in the positive lead as close to the panel as possible.

In this case, if the negative lead was switched, there would still be a complete circuit if the positive lead accidentally contacts ground anywhere on the boat.

If the panel output and controller input is floating, it doesn't matter which one is switched "open", no current can flow if either is.

[slowpoker]

Having the same controller you have and are now using, the manufacturer advises you first connect the battery positive and neg. and then connect the panels themselves, meaning that if you have the panels feeding the controller, there is no place for that power to go to and may cause problems.
They also require fuses for the battery positive and the panel positive. So.....just disconnect the fuse on the positive leads coming from the panels, either when working on the panel wiring or removing them or even a good place to test them! I use the proper amperage fuses as required in the instructions, using those plastic fuses with 2 legs as in automotive applications but the holders have a water resistant lid that covers the fuse itself. Easy pull out to disconnect or change or test!. Make sure the holders are rated for 30 amps, which come with 10 AWG wires on them. Mine are in the cabin, close to the controller for the panels and the battery fuse holders are, of course, near the batteries themselves, before the buss bar. Always have Battery power applied when connecting or disconnecting the panels.

[TheThunderbird]

Pulling off the fuse?

[Safari38LH]

Sorry for the thread drift, but does anyone have plugs on the deck to disconnect their panels or does everyone wire straight thru to the controller? I go straight through but see some advantage to being able to unplug right at the deck level. Is there such a thing as a MC4 deck plug?

[Hilbert]

Originally Posted by slowpoker

Having the same controller you have and are now using, the manufacturer advises you first connect the battery positive and neg. and then connect the panels themselves, meaning that if you have the panels feeding the controller, there is no place for that power to go to and may cause problems.
They also require fuses for the battery positive and the panel positive. So.....just disconnect the fuse on the positive leads coming from the panels, either when working on the panel wiring or removing them or even a good place to test them! I use the proper amperage fuses as required in the instructions, using those plastic fuses with 2 legs as in automotive applications but the holders have a water resistant lid that covers the fuse itself. Easy pull out to disconnect or change or test!. Make sure the holders are rated for 30 amps, which come with 10 AWG wires on them. Mine are in the cabin, close to the controller for the panels and the battery fuse holders are, of course, near the batteries themselves, before the buss bar. Always have Battery power applied when connecting or disconnecting the panels.

Solar panels are constant current devices. A fuse would need to be sized greater than their short circuit current Isc, which the panels themselves will not exceed. I have seen manufacturers recommend fusing on the panel side, but I would imagine that they would be hard pressed to justify the expense (if it was coming out of their pocket).

[DotDun]

Originally Posted by Hilbert

Solar panels are constant current devices.

?? They tend to be constant voltage with current varying with light intensity.

Originally Posted by Hilbert

A fuse would need to be sized greater than their short circuit current Isc, which the panels themselves will not exceed. I have seen manufacturers recommend fusing on the panel side, but I would imagine that they would be hard pressed to justify the expense (if it was coming out of their pocket).

MC4 fuses are ~$8... not much of an expense. IMO, it's worth it to protect the wiring to the controller.

[Hilbert]

Originally Posted by DotDun

?? They tend to be constant voltage with current varying with light intensity.

Solar panels behaves like a constant current source at high current. When shorted they can not exceed their maximum current. The wire should be sized for the maximum current that the panels can generate (or better yet for minimal voltage drop), therefore no fuse is needed.

Batteries are considered to be a constant voltage source. When when you short a battery the current goes very high and the circuit better be protected by a fuse.

[DotDun]

Originally Posted by Hilbert

The solar panel behaves like a constant current source at high current. When shorted they can not exceed their maximum current. The wire should be sized for the maximum current that the panels can generate (or better yet for minimal voltage drop), therefore no need for a fuse.

Batteries are considered to be a constant voltage source. When when you short a battery the current goes very high and a fuse is necessary.

You are correct, solar will not exceed it's maximum current output. If you watch the output, they reach rated voltage at first light, and current increases with sun intensity, hence they operated like a constant voltage device.

I differ with your opinion on needing a fuse, I would rather blow a fuse than put weld marks on the aluminum arch due to wire chafe.

[DotDun]

Originally Posted by Hilbert

Solar panels behaves like a constant current source at high current. When shorted they can not exceed their maximum current. The wire should be sized for the maximum current that the panels can generate (or better yet for minimal voltage drop), therefore no fuse is needed.

Batteries are considered to be a constant voltage source. When when you short a battery the current goes very high and the circuit better be protected by a fuse.

Actually, the more I thought about it, you are right, no fuse needed....