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Old 02-09-2012, 18:08   #1
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On Off Switch for Solar Panel

Is there any reason a fused on off switch can't be used to turn off a solar panel.The output of my panel added to the alternator output causes my tach. to fluxuate when motoring for long periods
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Old 02-09-2012, 18:18   #2
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Re: on off switch for solar panel

Connect the panels more directly to the batteries--they will act like big filters on the output. But, you can use a switch.
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Old 02-09-2012, 18:19   #3
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Re: on off switch for solar panel

Sure you can do this. Our panels have 20A breakers in the cockpit so that they can be turned on or off. Effectively functions as on/off switch and a breaker.
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Old 02-09-2012, 18:23   #4
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Quote:
Originally Posted by Kettlewell
Connect the panels more directly to the batteries--they will act like big filters on the output. But, you can use a switch.
And use a suitable size fuse. Your wires are hot and if connected need to be fused as near the source as you can.
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Old 02-09-2012, 18:58   #5
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Re: On Off Switch for Solar Panel

Good question...

Does it matter if the switch is before or after the controller?
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Old 02-09-2012, 19:00   #6
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Re: On Off Switch for Solar Panel

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And use a suitable size fuse. Your wires are hot and if connected need to be fused as near the source as you can.
But remember that in this case the battery can be the source as well. If I had to choose one location for this fuse it would be close to the batteries, since these can potentially pump out way more current than the solar panels. Better yet is to have a breaker close to the batteries, and a switch (or another breaker) close to the panels.

You may be able to use an existing breaker for the battery-side protection, but you run the risk of having that breaker pop and then the unloaded solar panel putting out 20V or so into whatever else is on the same side of the blown breaker. This is a good way to fry your electronics.

Bottom line, look at your fault scenarios and design accordingly.
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Old 02-09-2012, 19:23   #7
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Re: On Off Switch for Solar Panel

You probably want to takie your solar panels *offline* when the alternator is charging. The solar panel will *confuse* the smart regulator because it raises the voltage which is how the regulator determines how much to energize the alternator field and how many amps to pump out. I use a simple SPST push pull switch on the neg wire to take them off line when the engine is running.
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Old 02-09-2012, 19:38   #8
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Quote:
Originally Posted by Paul Elliott

But remember that in this case the battery can be the source as well. If I had to choose one location for this fuse it would be close to the batteries, since these can potentially pump out way more current than the solar panels. Better yet is to have a breaker close to the batteries, and a switch (or another breaker) close to the panels.

You may be able to use an existing breaker for the battery-side protection, but you run the risk of having that breaker pop and then the unloaded solar panel putting out 20V or so into whatever else is on the same side of the blown breaker. This is a good way to fry your electronics.

Bottom line, look at your fault scenarios and design accordingly.
Yep paul thats what i meant. Didnt say it as well as you.
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Old 02-09-2012, 21:28   #9
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Re: On Off Switch for Solar Panel

The tach is quitting because either the batteries are mostly charged or the alternator regulator voltage setpoints are too low.

If you have a solar controller, there will be no confusion with the engine alternator. The battery will accept all current from all sources until it reaches a higher state of charge. After this point, charging sources will start to roll back current - the exact ones and order determined by the setpoints on the regulators/controllers.

At some point, either the alternator or solar will predominate. If solar, then the alternator regulator will shut down and the tach will go out.

Shutting the panels off just removes a charging source and delays the point at which the tach quits. When this point is reached, try turning on something that draws power from the batteries and drops the voltage.

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Old 02-09-2012, 21:43   #10
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We have multiple DC charging sources and do need to isolate the solar regulators so that the other regulators function appropriately. To solve this consider installing a 30A auto relay (if appropriate for your solar array size) between the PV's and the solar regulator. They are cheap and very reliable. Wire this so that the panel connects to the normally closed terminal of the relay. This then allows for a low current wire on the relay coil to be run to a low current switch in a convenient place. I have used this method for years and it solves the tach and other issues well.
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Old 02-09-2012, 22:15   #11
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Re: On Off Switch for Solar Panel

It seems we've had this discussion before in another thread...

I too have had the interaction between solar panels and alternator, which resulted in the cycling on/off of the alternator every few seconds. Very annoying. So I shut off the panels with a switch located between the panels and the solar regulator. I agree with the earlier comments that the breaker or fuse needs to be just before the battery, while the switch is probably better placed between the solar panels and controller.

All of my charging sources (alternator, wind vane, solar panels - except the battery charger) are connected to the batteries through isolator diodes. Besides assuring that all batteries get charged, it prevents shorts in the wiring or charge devices from dumping the power from the batteries and starting a fire. Recently I bought a dual output Morningstar solar regulator so I will be using fuses instead of the diodes for solar. I already have fuses on the wind generator (in addition to the diodes) and battery charger connections.

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