Please critique my solar plans

[TeddyDiver]

Originally Posted by mitiempo

Only wire the panels in series if there is zero chance of shading. Likely there will be shading at times.

A question regarding your statement. I believe it's true only with panels with a single or few bypass diodes. However some panels have them installed in every individual cell so there's no way with shading problems in series as long as the cell's in the panel are in series as well. I'm I right in my reasoning?
And further, how can I know the number of bypass diodes in solar panels, most manufacturer's don't mention about it. I've seen this information only in some Chinese panels..

BR Teddy

[vtomanov]

Change to LiFePo4 about 400ah and put at least 500-600W solars with MPPT ,

I have a 34 boat and my solars are 240W + windgen 400W and I'm running low on power - searching for space for another 250W solars..

http://mantis.b2net.net/dw/wind_solar.JPG

[twinboat]

Originally Posted by Privilege

I have a breaker between my panels and controller. It's important to be able to easily turn them off if you are working on the electrics, not to mention the protection they afford. It's not necessary to have another one near the battery (assuming that we are talking about the solar system only).

Solar panels are a power producing device. If you use a breaker in them, the breaker needs to be rated higher then the output of the panels. It will never blow.

They offer no protection only a way to switch off the power in this situation.

You also need to use wiring capable of carrying the load from the panels, so again no breaker needed in systems of 1 or 2 panels.

With multiple panels running to junction box's, breakers are needed for protection from 2 or more panels back feeding to 1 shorted one.

On the battery to controller wiring, a fuse or breaker is absolutely nessessery. If the controller, or wiring to it, shorts out, the battery has enough power to melt the wire and cause a fire.

The breaker need to be close to the battery to protect as much of the wire as possible and rated to blow before it's melting point. Breakers protect wires, not batteries.

[jbinbi]

Originally Posted by twinboat

Solar panels are a power producing device. If you use a breaker in them, the breaker needs to be rated higher then the output of the panels. It will never blow.

They offer no protection only a way to switch off the power in this situation.

You also need to use wiring capable of carrying the load from the panels, so again no breaker needed in systems of 1 or 2 panels.

With multiple panels running to junction box's, breakers are needed for protection from 2 or more panels back feeding to 1 shorted one.

On the battery to controller wiring, a fuse or breaker is absolutely nessessery. If the controller, or wiring to it, shorts out, the battery has enough power to melt the wire and cause a fire.

The breaker need to be close to the battery to protect as much of the wire as possible and rated to blow before it's melting point. Breakers protect wires, not batteries.

good clarification on previous post.

was clear that i needed a fuse/breaker to protect wires from controller to battery. not sure post before said that, so good info.

also clear that breaker between panel is just really on off switch.

NOT clear, and hoping for some advice on
1. Have 2 (or more panels) , these are 30v soc @ 9amp ioc, and if i go to single controller
a. if i want a breaker for a switch, should i put both panels into single breaker, and if so, what rated breaker do i want
b. if i do this, do i want to actually use a bus bar first, putting both panels into that, then taking a single wire into a breaker.

2. sort of the same question assuming no breaker now, do i put both panels into the same input connector on the controller, or again, use a bus bar to combine panels, then use a single wire onto the contoller.

3. assuming i use 2 controllers, then question on wiring from controller to battery.
a. do i want to combine the outputs onto a bus bar, then take a single wire to the battery (through a fuse/breaker which is protecting that wire) or
b. take 2 wires, one from each controller to the battery. and if i do that, should i put both wires onto the same battery connector (not sure what this is called, but it goes over the battery post, and usually has wing nuts) or get a connector that has multiple wing nuts.

appreciate if someone who has done this or has marine electrical background could comment. thanks.

[mitiempo]

Originally Posted by jbinbi

NOT clear, and hoping for some advice on
1. Have 2 (or more panels) , these are 30v soc @ 9amp ioc, and if i go to single controller
a. if i want a breaker for a switch, should i put both panels into single breaker, and if so, what rated breaker do i want
b. if i do this, do i want to actually use a bus bar first, putting both panels into that, then taking a single wire into a breaker.

2. sort of the same question assuming no breaker now, do i put both panels into the same input connector on the controller, or again, use a bus bar to combine panels, then use a single wire onto the contoller.

3. assuming i use 2 controllers, then question on wiring from controller to battery.
a. do i want to combine the outputs onto a bus bar, then take a single wire to the battery (through a fuse/breaker which is protecting that wire) or
b. take 2 wires, one from each controller to the battery. and if i do that, should i put both wires onto the same battery connector (not sure what this is called, but it goes over the battery post, and usually has wing nuts) or get a connector that has multiple wing nuts.

appreciate if someone who has done this or has marine electrical background could comment. thanks.

1. It depends if the panels are in series or parallel. You want the breaker rated higher than the amperage the wire will carry by a fair margin. Or you could use a switch rated for more than the expected current.

2. Depends where you are connecting the panels. Most connect the panels outside and run 2 wires below. The controller output should go to buses and they are wired to the battery bank - positive and negative. Keep the wires on the battery bank to a minimum - ideally only 1 positive and 1 negative. Wing nuts should not be used on batteries.

[mitiempo]

Originally Posted by TeddyDiver

A question regarding your statement. I believe it's true only with panels with a single or few bypass diodes. However some panels have them installed in every individual cell so there's no way with shading problems in series as long as the cell's in the panel are in series as well. I'm I right in my reasoning?
And further, how can I know the number of bypass diodes in solar panels, most manufacturer's don't mention about it. I've seen this information only in some Chinese panels..

BR Teddy

Any shading can reduce output, regardless of panel design. My preference is one controller per panel. The only exception is if there is no possibility of any shading - like the upper deck of a powerboat. On a sailboat there will at times be shading.

[socaldmax]

Originally Posted by mitiempo

Any shading can reduce output, regardless of panel design. My preference is one controller per panel. The only exception is if there is no possibility of any shading - like the upper deck of a powerboat. On a sailboat there will at times be shading.

That's not entirely true. Sunpower seems to be the only panel that suffers from far lower shading losses due to their unique design.

On smaller systems, I might also recommend one controller per panel, but on larger systems you start running into other practical considerations. This current system we're installing with 4 285 watt panels is using 2 60 amp controllers, meaning that even though we are connecting the panels in series, we're using 6 GA boat cable and 2 sets of those completely fills up a 1" dia. support pole. We're using 4 GA cable from the controllers to the DC bus bars, even though they're only about 7 or 8 ft away, for minimal resistance. Also, all of the cabling cost as much as 2 of the panels, and that's with 2 panels per controller!

If one were to use cheap $100 controllers per panel, you could offset the cost of expensive cable and connectors.

[twinboat]

May not be right but I ran 12 gauge wire 8 feet from 3, 225 watt, 36 volt, series wired panels. I used a household wall switch to turn off the panels.

Shading is not an issue on my Trawler.

I have one TriStar MPPT 60 controller.

The cable from the controller to the battery buss is 24 inchs long and I believe 6 gauge. It has an 80 amp fuse.

4 years running and all is well. We full time on a mooring.

[socaldmax]

Originally Posted by twinboat

May not be right but I ran 12 gauge wire 8 feet from 3, 225 watt, 36 volt, series wired panels. I used a household wall switch to turn off the panels.

Shading is not an issue on my Trawler.

I have one TriStar MPPT 60 controller.

The cable from the controller to the battery buss is 24 inchs long and I believe 6 gauge. It has an 80 amp fuse.

4 years running and all is well. We full time on a mooring.

Well, to each his own, but I wouldn't recommend 12 ga even for speaker wire.


I had a customer that I installed 3 210 watt solar panels for, and afterward he asked me to take a look at his audio system. He had some very nice speakers, but the sound was distorted at any decent listening levels.

I upgraded his amp, power cables to 4 ga, speaker cables to 10 ga and the difference was enormous! The point being, sometimes you don't realize the ill effects of too much line resistance until you upgrade.

[mitiempo]

Originally Posted by socaldmax

If one were to use cheap $100 controllers per panel, you could offset the cost of expensive cable and connectors.

I do not recommend that. For panels under 200 watts I like Victron 75/15 controllers. A fast fully programmable MPPT controller.

[socaldmax]

Originally Posted by mitiempo

I do not recommend that. For panels under 200 watts I like Victron 75/15 controllers. A fast fully programmable MPPT controller.

I would. For panels 300 watts and under I like the Eco-worthy 20 amp MPPT panel. I've installed over a dozen of them and they perform great. Fast MPPT, easy to read display, large gold plated terminals, super easy setup via the menu, can be programmed to absorption charge in .1v increments.

Those Victron controllers do look nice, especially the high input voltage, but that's kind of a moot point if you're only connecting one panel to it. I'm a little disappointed in how small the holes are in the terminal strip, it forces you to use smaller wires or a short section of smaller wires.

[jbinbi]

I looked at the Eco Worthy, their controller is 20, but my panels are 285 watts, I am not sure even 25 amps is OK? I know the panels are like 24 , shouldn't there be head room?

Sent from my YOGA Tablet 2-1050F using Cruisers Sailing Forum mobile app

[socaldmax]

Originally Posted by jbinbi

I looked at the Eco Worthy, their controller is 20, but my panels are 285 watts, I am not sure even 25 amps is OK? I know the panels are like 24 , shouldn't there be head room?

Sent from my YOGA Tablet 2-1050F using Cruisers Sailing Forum mobile app

They are rated at 300 watts, keep in mind you'll probably never get full rated power out of a solar panel, even brand new, due to the way they are tested vs real world conditions. I have installed two of them with 410 watts of solar panels on them and they will produce 22 amps if there's enough current draw.

The theory behind putting 410 watts on a 20 amp controller was because the owners used them only in the winter, so in the summer they were only maintaining charge, in the winter they produced much closer to 20 amps than they would have with only 300 watts of panels per controller.

Yours would be much closer to the 300 watt rating per controller, you'd probably see peaks of 14-15 amps in the winter, closer to 18-19 amps in the summer (per controller.)

[vtomanov]

Practical experience - 240W panels generally ( if not at the equator) e.g. in the med are producing about 5ah-10ah ( mostly 5ah) e.g. if you want to have juice for more then your fridge from the solars - better go for at least 500W

[mcarling]

Originally Posted by mitiempo

You want the breaker rated higher than the amperage the wire will carry by a fair margin.

To clarify: The breaker should be rated higher than the current the wire is expected to carry but lower than the current the wire is capable of carrying.