Help...Wiring 12 Solar Panels

[ski69sail]

Thanks in Advance for your advice

I intend to wire 12 x 60 watt Sunpower solar panels on my rear davits. I have a single MPPT charge controller that is rated for the watts and amp hours with suitable tinned cable.

My concern is how to connect all the individual solar panels together ???

Thank You

[Pete7]

You have a choice either parallel or in series if you are using a MPPT. In series you get 24v which the MPPT will then convert down to maximum advantage but if there is any shading then it will seriously degrade the amount of power. Alternatively in parallel you get 12v so less for the MPPT to play with, but if one panel is shaded then whilst that will stop providing a charge the other panel in sunlight will continue to charge.

which is the best? hmm, yes an interesting question and there have been some interesting recent threads on this.

I couldn't decide and in the end opted for a single 150w solar panel, but 2 x 80w panels was under serious consideration so I could wire them either in series or parallel. In the end i went for the KISS approach and the big single, but 2 smaller panels wouldn't be wrong.

Pete

[StuM]

Either Pete7 or I is/am misinterpreting you. 12 x 60W panels on your rear davits? Really? That's going to be about 6 sq metres which is lot of real estate hanging off the back of a 40ft monohull.

If you really have 12 panels, you probably need to wire them up in both series and parallel. They are probably about 18V operating voltage, so putting them all in series is likely to be putting out well over 200 Volts. Putting them all in parallel will not give you enough voltage for the MPPT controller to use effectively.

What is operating voltage of each panel? What is the rating of your MPPT controller (Max watts and volts)?

The fact that you talk about your controller being rated for "amp hours" suggests that you need to spend a little more time learning how DC electricity, solar panels and controllers work.

[Pete7]

Originally Posted by StuM

Either Pete7 or I is/am misinterpreting you.

Oops I read that as 2 x 60w panels not 12. The only thing you could get 12 panels mounted on would be something like this.

[LoudMusic]

Guys, 60w panels are really small. Like 2'x2'. Twelve of those is only 48 sq ft, or 4.5 square meters. The beam on a Ganley Transition 41 (noted in his profile) is 12'9". That could hang two rows of 6 solar panels and only be 4 feet deep off the stern. Or even if he went to three rows of 4 panels, that'd only hang 6 feet off the stern.

Regardless ... I agree you want to have enough voltage for the MPPT to play with, but not go over its rated maximum input.

Stu is right - terminology is very important when dealing with electricity. Make sure that you understand the numbers you are reading on the equipment and that everything plays nicely together. It's a sad day when you fry parts that cost hundreds of dollars each just because of a maths translation error.

[noelex 77]

The evidence is not quite definitive, but it suggests parallel connection is the best option. So if you have a 12v battery system and can install cable of suitable diameter, this is way I would arrange them. The only exception is some of the new Victron controllers that have an unusually high start up voltage.

720 w is a lot to get on the the davits of a 41 foot steel boat, but this will give you heaps of power if you can make it fit.

It would help to know somemore details such as the Vmp of your panels, battery system voltage (12 or 24v) and the proposed controller.

[ski69sail]

Hi Everybody

The MPPT is a 40A EPsolar MPPT LCD Solar Panel Battery Regulator Charge Controller 12V/24V FB

The solar panels are 60 watt max power.
Max Power Current 3.39A
Size is 440mm x 560mm rigid

I intend to mount the solar panels on two separate sheets being 1120mm wide and 1320 long each. Total width 2240mm x 1320mm long. My radar is in the middle of the davits so shading will occur.

My concern is how to join all the solar panels together without burning them out. I am concerned about the high cumulative watts and amps feeding back to each individual panel.

I have 2x12 volt Lifeline AGM 220 amp hour batteries wired as 12 volt

Thank You

[StuM]

Originally Posted by ski69sail

Hi Everybody

The MPPT is a 40A EPsolar MPPT LCD Solar Panel Battery Regulator Charge Controller 12V/24V FB

The solar panels are 60 watt max power.
Max Power Current 3.39A
Size is 440mm x 560mm rigid

I intend to mount the solar panels on two separate sheets being 1120mm wide and 1320 long each. Total width 2240mm x 1320mm long. My radar is in the middle of the davits so shading will occur.

My concern is how to join all the solar panels together without burning them out. I am concerned about the high cumulative watts and amps feeding back to each individual panel.

I have 2x12 volt Lifeline AGM 220 amp hour batteries wired as 12 volt

Thank You

You haven't told us the most important fact: What is the operating voltage of the panels. (Generally listed in the panel documentation as Vmp )

According to specs here:
EPsolar 10A/20A/30A/40A MPPT Solar Panel Battery Regulator Charge Controller FB | eBay

The maximum voltage for that controller is 100 Volts. Assuming that your panels Vmp is around 18V, with an open circuit voltage of around 30 Volts, that means that you wouldn't wont to have more than 4 panels in series in your system.

But worse, the maximum PV input power for 12V is only 510W.

In other words, contrary to your belief, your controller can't handle the 720W from 12 x 60W panels going into a 12V system.

[StuM]

Originally Posted by ski69sail

The MPPT is a 40A EPsolar MPPT LCD Solar Panel Battery Regulator Charge Controller 12V/24V FB
The solar panels are 60 watt max power.
Max Power Current 3.39A
Size is 440mm x 560mm rigid

Are you quite sure about that size? That's 0.246m². Which would mean that the panels are about 25% efficient, which would be outstanding.
60 W panels are generally quite a bit larger than that.

[noelex 77]

Originally Posted by StuM

You haven't told us the most important fact: What is the operating voltage of the panels. (

From the other information we can calculate the Vmp. With a wattage of 60w and Max Power Current 3.39A the Vmp must be 60/3.39 = 17.7v.

This is slightly lower than average for a "12v" solar panel, but most MPPT controllers will work OK with this voltage unless the panels are mounted in a location where they will get very hot (such as no ventilation underneath). Therefore, I would wire the panels in parallel for optimum output.

Originally Posted by StuM

But worse, the maximum PV input power for 12V is only 510W.

In other words, contrary to your belief, your controller can't handle the 720W from 12 x 60W panels going into a 12V system.

+1. A different controller is needed. Personally I would be wary of these cheap "no brand" MPPT controllers. They frequently do not work well, have poor durability, or both.

[noelex 77]

Originally Posted by StuM

Are you quite sure about that size? That's 0.246m². Which would mean that the panels are about 25% efficient, which would be outstanding.
60 W panels are generally quite a bit larger than that.

+1. There is something wrong with those numbers. The panels must be larger, or the 60W is a mistake. The very best comercial panels are made by Sunpower themselves. These are just over 22% efficient.

25% is not possible for a commercial panel.

[ski69sail]

Hi There

The panels are reputed to be made with Sunpower solar cells in China.They look like the end of a production run dumped on the Aussie market. I picked them up and bought them back to New Zealand.

I beleive the specifications are probably a little optimistic
My marine electrician recommend the MPPT controller brand
Max Power Voltage 17.7V

Live and lean and keep paying

Thanks

[Madehn]

2 feet by 2 feet is about right for a 60 watt panel as i just added two with similar specs to my boat. i have just shy of a kilowatt of solar - all wired in parallel -- with an outback flexmax 80 controller-- if i had to do it over again i would have wired in series at a higher voltage and used a smaller gauge wire as pulling that thick wire for the distances i needed was both expensive and hard to do.

[StuM]

Originally Posted by Madehn

2 feet by 2 feet is about right for a 60 watt panel as i just added two with similar specs to my boat. i have just shy of a kilowatt of solar - all wired in parallel -- with an outback flexmax 80 controller-- if i had to do it over again i would have wired in series at a higher voltage and used a smaller gauge wire as pulling that thick wire for the distances i needed was both expensive and hard to do.

Yes, that's 610 x 610mm = 0.372 m². Which is 50% larger than the OP's stated 440 x 550mm. (And would be about right at around 16% efficiency).

48 sq ft is still a lot of real estate over the stern of a 40ft monohull. That's about what I've got on a 7 metre beam cat.

[UNCIVILIZED]

You trying to build a DIY arc welder? That' a lot of juice!