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Wiring a Marine Solar System

10/13/2015

18 Comments

 
PictureWiring Diagram for a Two Solar Panel System, a Dual Output Solar Controller and Two Battery Banks
We are often asked questions about how to wire a solar system.  This can appear to be a daunting task for those new to the world of solar but it is actually quite easy and straight forward.  In this blog I will walk you through the wiring process for our dual output controller step by step.

First, the definition of a few terms:
​* MC4 Connector - A water proof connector used in solar wiring.  Most solar panels come with MC4 connectors attached to 3 foot solar wire pigtail coming from the panel junction box.  These connectors are easily disconnected.
* Solar Controller - Except for small trickle charge systems, all solar systems should have a solar controller.  The purpose of a controller is to prevent batteries from being overcharged, apply the optimal charging current to the battery bank and prevent current from back flowing from the batteries to the solar panel at night.  Controllers are sized by their amperage capacity.  Controllers designed for residential and commercial (lighting) use are generally overkill and not well suited for marine applications.
* Temperature Sensor - This device is connected to the controller and senses the temperature of the battery bank.  If the batteries are heating up due to heavy charging, the sensor signals the controller and the controller reduces the charge current appropriately. A temperature sensor is only useful for systems with larger solar arrays as smaller solar systems do not provide sufficient power to over heat the batteries.
* Solar Wire - While most any wire can be used in a solar system, solar wire is designed for maximum conductivity and is well insulated with a UV resistant cover.  It is typically single conductor and the insulation is .25 Inches in diameter.

The wiring diagram below is taken from our dual output controller manual and illustrates the basic wiring required for a two panel system, a dual output controller and two battery banks.  Most solar controllers are single output so charge only one battery bank. In this case, it is common to wire the positive wire to the common on the battery 1-2-both battery switch to select which battery bank is to be charged.







​
A few things to note in the diagram:
* The two solar panels are wired in parallel using an MC4 T-branch connector,  If one panel is shaded, the other panel will still provide full power to the controller.
* There is a switch in the positive wire between the solar panel and the controller.  This is optional.  The purpose of the switch is to turn off the panel should it interfere with the alternator output when the auxiliary engine is generator is running. It has been reported that some smart regulators are confused by the power coming from the solar panel.  It sees the sum of the battery charge plus the panel output and senses the batteries are fully charged so goes into float mode prematurely.  This is easily remedied by flipping the switch thus disconnecting the solar panel.
* The optional temperature sensor is shown to the left of the larger house battery bank.  It is simply taped on to the top of the battery.
* If you have a battery monitor such as a Link or Xantrex 1000 or 2000, it is important to connect the  negative wires from the controller to the shunt of the battery monitor.  Otherwise, the monitor doesn't see the power coming in from the solar panel and will give inaccurate readings.
* There is a sequence to follow in connecting the solar system.  Connect the controller to the battery banks first.  Then connect the solar panel to the controller.

​

Picture
Picture
A Set ofMC4 T-branch Connectors
Picture
Cross Section of Solar Wire Illustrating Insulation Layer and UV Protection Layer
Picture
Example of a Battery Monitor Shunt
18 Comments
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11/16/2018 01:14:24 am

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Reply
Rol Lloyd
4/14/2019 01:53:17 pm

I have a 2 bank battery system on sailboat. Two 12 vdc batteries in parallel and one 12vdc battery (STARTING). Show me a schematic for a 2 50w solar panel to keep both banks charged. Also with a switch to disconnect the solar panels.

Tks
Rol

Reply
tony
12/26/2020 11:29:29 am

Hi,
I have a similar requirement. Consider this-if a suitably rated diode is inserted between the battery and the pv regulator to block any current flow into the regulator from the battery and the charge it is receiving from the engine, then the regulator should be protected without having operate any switches manually.

Reply
Jim Young
7/6/2019 08:15:51 am

Hi Tim,
Good article.
I recently installed solar panels as you have described above. I was told I need to "turn off"/cut the solar panels when my sailboats engine and alternator are running, otherwise I may blow the controller. Every time I turn on the engine, I am engage a cut off switch installed. When I am on the hook or at the dock, I reengage the solar panels by turning the switch back on. Do you have any thoughts on this or is there an auto switch that will engage when the engine is on and disengage when off, so solar panels will charge the batteries. Thank you. Jim

Reply
Charles
10/13/2022 08:28:25 am

Jim, you should be able to use a relay with a Normally open/Normally closed terminal. When engine is off (relay in normally closed) connect that terminal inline with the solar charging. Use your relay control wires to loop in to the ignition circuit of your boat engine, thus when you start the engine, it opens the relay, allowing your alternator to charge the batteries, and when you shut the engine off, the relay closes, allowing solar to charge the batteries.

Reply
Guy Pratt link
11/14/2022 10:17:37 am

I'm curious if this would work for an option to charge batteries with a 120V house line. I.e. batteries can be charged through solar, but when home (trailer sailor), can be plugged into outlet to charge.

Elliot Keller link
1/7/2021 05:19:25 pm

Great blog yoou have

Reply
Mark
4/23/2021 05:36:08 pm

Good evening
Please can you help.
This is an approximate list of what I would envisage using in a average week.
Obviously I would never be using all of the equipment at the same time.
Many thanks
Mark 07854523434

1. 230 volt Washing machine once a week. ( 1 day pw for 2 hours )
2. 230 volt Tv every day ( 6 Hours per day )
3. 230 volt Microwave 5 times per week ( Once per day for 10 minutes maximum )
4. 230 volt Toaster 5 times per week ( Once per day for 5 minutes maximum)
5. 230 volt Fridge freezer every day ( All day every day )
6. 230 volt Oven once a week ( Once per week for two hours maximum )
7. 5 volt Mobile phone chargers every day x2 ( Once per day each 1 hour each )
8. 12 volt Shower fan. ( Twice per day every day 10 minutes)
9. 230 volt Hair dryer 5 times per week ( 5 Days per week for 5 minutes maximum per day)
10. 12 Volt Lights every night. ( 6 hours per day)
11. I Pads x 2 every day. ( 3 hours per day )
12. 12 volt Toilet pump every day ( Every day 1/4 hour per day )
13. 12 volt Fresh water pump every day. ( Every day 2 hours per day )
14. 12 volt Waste water pump ( Every day 1/2 hour per day )
15.12 volt Shower pump every day (Twice per day every day total 20 minutes maximum)



Dear custom marine products
Please can you help.
I have a 60 ft x12 ft wide beam canal boat with a Victron energy Blue Power Multiplus 12volt / 3000va / 12Amp Inverter.
I am not an electrician but I have a good friend of mine who has asked me to find out as much information as possible from you guys so he knows what system to fit for me.
Would it be possible for you to supply me drawing or information for him to fit the the right size and power solar panels and batteries so that I can live off grid for approximately 3-5 days at a time without connection to shore power. I have guessed I need approximately 12-14 hundred watts of power. This is just an assumption. This is where you guys come in to help us and give us you expert advice and information.
My friend totally understands the Amps, Volts, Amph, Watts, the charging and distribution side of solar panels but he would need a drawing or graph of what you think would be needed.
I understand that you need the total of Watts, Klwts, Amps, Hours of use etc etc. But he has suggested to me that once he knows the power inlet and outlet of the panels and what batteries you suggest he can work out what I can and can’t use on the boat.
So would it be or is it possible for you to tell us We have this system that can supply you this much power or we we have this more powerful system that can supply you that much power.
Once we know what system that you can advise he can work around that and fit the right Panels, Batteries, Isolators, etc and what cable and other equipment and fittings needed.
Once we have all the information you can supply we would also like you to give us the price of the equipment and delivery times if you don’t mind. We would like to have all your equipment supplied and fitted within the next two weeks if you can deliver it within that time, if not we don’t mind waiting another week if need be. The reason I ask this is we have our boat out of the water about one mile from where we live at the moment and we have just started to pay for the marina where it will be moored so we would love to have all your equipment fitted within the next two weeks so we don’t have to pay for two moorings.
I hope I have made sense as I am not an expert in solar panels and 12volt electrics. I would appreciate as much help as possible.
Many thanks for your help and understanding.
Mark Moulsdale
66 Beaufort street
Southend on sea
Essex
Ss24nh
078545523434

Reply
Jay
6/12/2021 12:47:00 am

Hello my solar charges good during the day but at night time it just dies what could be draining the batteries nothing is plugged in also

Reply
Best Access Doors link
10/8/2021 08:32:40 am

The simplicity of your presentation is highly-motivating for learning. Please keep it up for your teeming followers.


Reply
Access Doors and Panels link
10/8/2021 08:35:20 am

Good article with an excellent way of presentation. Keep it up. Thanks for sharing.


Reply
Ruby Layak link
11/30/2021 05:24:19 am

Very User friendly. Simple without many ads.

Reply
Mia Evans link
1/11/2022 03:40:23 am

Thanks for pointing out that a temperature sensor would help sense any overheating in batteries. With that in mind, it would definitely be a good investment to have that kind of marine equipment system. My brother should know about this now that he wanted to get his own boat now that he moved into a new place near the lake.

Reply
Elaine
3/8/2022 07:57:47 am

Thank you for sharing this piece, it's a great topic.
By the way, I just want to share this piece about sustainable living: https://www.superdraft.com.au/trends/solar-power-battery-system
I think it's something worth sharing!

Reply
Elaine
3/8/2022 08:24:07 am

Thank you for sharing this piece, it's a great topic.
By the way, I just want to share this piece about sustainable living: https://www.superdraft.com.au/trends/solar-power-battery-system
I think it's something worth sharing!

Reply
Bianco Electric link
1/22/2023 11:43:02 am

Thanks for sharing this tip, really informative and helpful. I'd be using this for my upcoming post. We must all accept it, the value and importance of our role as electrician helping every household be safe including installation of solar power systems. Totally should be done by a pro

Reply
Lance White
3/2/2024 05:09:29 pm

I have a 4 6 volt battery set up (4- 240 amp-hours=960 amp-hours, a tracer 3215rn controller (spec max input voltage = 300 watts @ 12 Volts) and 2 - 300 watt panels (Heliene 72M-360).
I will wire the two panels in parallel with a diode on both positive
legs.
Are the 2 panels going to overload the controller?

Reply
Tom Trimmer link
3/3/2024 12:58:35 am

Lance,
Our rule of thumb is 130 Watts of solar per 10 amp capacity of controller. So, the 30 amp Tracer has a capacity of roughly 390 watts. You will need a controller with 45 amp capacity for 600 watts of solar.

Reply



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    Thomas Trimmer has been cruising with his Ericson 38 sailboat on the Great Lakes for over 20 years.  He has pioneered the use of solar energy for wilderness cruising.  He is continually designing and building equipment to simplify and enhance the cruising experience.

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  • Home
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