Splicing solar panels together.

[shanker]

Hey Sumner,

I love that deal for the 40 watt panel. Is that the same style that you used? I am going to mount off the stern similar but different from your install. Is that panel pretty sturdy/durable. It sure sound like a heck of a deal.

I currently have a 5watt Brundson panel and it came with a charge controller. Would I be able to use that controller with this 40 watt unit? How are these units rated or how can I test it to make sure it can hanle the new panel?

Thanks,

Shanker

[Wind Chime]

by Catigale » Thu May 03, 2012 5:33 am

I have at least a 20 minute to one hour run back to the marina under power, and have always thought that was enough to recharge that batteries, so I just have the small solar panel to keep it topped up during the week.

Windchime - have you ever calculated your typical electrical loads? One hour of run time with a 200 Watt Alternator will replenish at most 20% of one group 24 battery capacity and more likely about 10% of same.

The outboard motor only charges about 20% an hour? I didn’t know that, great to know. Thanks!

To be honest, I don’t know how to calculate my D/C power usage? I am a competent skipper, but a poor electrician … help please

- Under sail we use a: chart plotter, autopilot, and VHF.
- At anchor: cabin lights, chart plotter at night for anchor alarm.

We have 2 group-24 batteries with a West Marine Combiner in-line between them, no 3-way switch. As well as another group-24 that is only connected to the A/C charger with nothing drawing off it (a just in case back-up because I don’t know how to calculate usage )

To check battery levels, all I have is one of those cheezy handheld units with an led read out of green, yellow, red.
We anchor usually just one overnight, maybe two. Longer trips we are at the dock on shore power most of the time.

[Sumner]

Hey Sumner,

I love that deal for the 40 watt panel. Is that the same style that you used? I am going to mount off the stern similar but different from your install. Is that panel pretty sturdy/durable. It sure sound like a heck of a deal.

I currently have a 5watt Brundson panel and it came with a charge controller. Would I be able to use that controller with this 40 watt unit? How are these units rated or how can I test it to make sure it can hanle the new panel?

Thanks,

Shanker

The panel...

http://www.solarblvd.com/Solar-Panels-& ... _info.html

.... looks to be the same as the one we got from them and installed at first alone here...

http://purplesagetradingpost.com/sumner ... de-22.html

You could probably just run braces directly to the panel frame sides and skip the mount under it that I made. The frames are pretty rigid. I've seen others do that.

On the controller it is hard to tell what you have without looking at it. Check out Maine Sail's page here...

http://www.pbase.com/mainecruising/solar_panel

... and read about the 3 types of controllers aways down the page. You don't want the 'shunting type'. We started with the one I gave a link to in the other post and it is a PWM controller and it worked fine. Now with the larger array we went with a MPPT controller for maximum efficiency as you run out of room to put additional panels on the boat. You don't need that for 1 40 watt panel. It would work, but I don't think you would see much difference over the $25 controller. Make sure your wire size is large enough.

Let me know if I can help more,

Sum

===================================
Our MacGregor 26-S

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

[shanker]

Hey Sumner,

Thanks for your help. I googled this solar charge controller and it seems as though it can handle up to a 105 watt panel. The PO must have installed it with this 5 watt panel he had. The instructions show that it doesn't come with this panel. They sell for $29.99. So I should be good with the 40 watt panel you posted which I'm going for!

FYI. on the solar controller: Load: 7A maximum
Cut-out:14.2 V
Cut-in: 13 V

One other question. It was asked to make sure I use the appropiate gauge wire. How do I determine that?

Shanker

[Sumner]

Hey Sumner,

Thanks for your help. I googled this solar charge controller and it seems as though it can handle up to a 105 watt panel. The PO must have installed it with this 5 watt panel he had. The instructions show that it doesn't come with this panel. They sell for $29.99. So I should be good with the 40 watt panel you posted which I'm going for!

FYI. on the solar controller: Load: 7A maximum
Cut-out:14.2 V
Cut-in: 13 V

One other question. It was asked to make sure I use the appropriate gauge wire. How do I determine that?

Shanker

Are you sure that isn't a 'shunting' type controller? From the specs it sounds like one to me with the cut-out and cut-in figures. Do you have a brand/model number? If it is a shunting type I would not use it, spend the $25 on the other one to get more from the panel.

On the wiring here is a good calculator ....

https://www.colemanair.us/vp_asp/Script ... reSize.htm

...I used the recommended 2% max power loss and 20 feet one way from the panel to the batteries (through the controller) and the 2.3 amp max on the panel and got #12 wire size. At 15 feet one way #14. Don't skimp on the wire size. I used a #16 for a short run from the panel to inside the lazarette to the controller and then much heavier wire forward to the batteries.

Be careful using the different calculators out there and see if they want the one way distance or the round trip distance (from the battery to the panel and back). That makes a huge difference. You don't have to get as picky with the rest of the wiring and can have larger voltage drops.

Good luck,

Sum

Our MacGregor 26-S

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

[shanker]

Thanks Sumner.

I don't know what a shunting controller is. Nowhere in the instructions do I see a reference of 'Shunting'. I will do some research on that term. There is no model number on this unit in the instrctions.

The instructions state:
"The charging Controller indication green light will light up when the battery voltage reaches 14.2 volts and the SCC (Solar Charge Controller) will prevent the solar panel (s) from overcharging the battery. It is normal for the SCC LED to light on and off as the battery voltage cuts in and out."

"When battery reaches below 13V, the SCC will cut in and charging begins"

Under FAQ for the Solar Panel:
1. Will panel drain battery at night?
A. No, this panel includes a blocking diode to prevent battery drain and reverse current.

Like I said, I will look into 'Shunting' to see what that means.

Here is a link http://www.backcountry.com/brunton-sola ... ge-monitor

Shanker

[Sumner]

Thanks Sumner.

I don't know what a shunting controller is. Nowhere in the instructions do I see a reference of 'Shunting'. I will do some research on that term. There is no model number on this unit in the instrctions.

The instructions state:
"The charging Controller indication green light will light up when the battery voltage reaches 14.2 volts and the SCC (Solar Charge Controller) will prevent the solar panel (s) from overcharging the battery. It is normal for the SCC LED to light on and off as the battery voltage cuts in and out."

"When battery reaches below 13V, the SCC will cut in and charging begins"

Under FAQ for the Solar Panel:
1. Will panel drain battery at night?
A. No, this panel includes a blocking diode to prevent battery drain and reverse current.

Like I said, I will look into 'Shunting' to see what that means.

Shanker

Here is a quote from Maine Sail's site....

Shunting Controllers = These controllers shunt or switch the panel current/voltage OFF when a preset voltage is reached and then turn back on when the battery bank voltage drops/falls to a second preset ON voltage. These are the least desirable controllers. If a controller does not specifically say PWM or MPPT is is probably a cheap shunting controller. I can not suggest spending your hard earned money on shunting controllers for a marine solar application. (SEE VIDEOS BELOW FOR ACTUAL BEHAVIOR)

Here is the link to that page...

http://www.pbase.com/mainecruising/solar_panel

From your description I'll bet that is what you have and spending $25 on the PWM one that I linked to or another 'true' PWM one would be a very good idea if you want to get the most out of that panel.

It sounds on the surface like the 'shunting' type would work just fine, but there is a lot more to efficiency than just hooking the panel to the battery. Understanding the controller types takes a little study. Here is a pretty good primer...

http://windsun.com/ChargeControls/ChargeCont.htm

... and another on why the MPPT....

http://windsun.com/ChargeControls/MPPT.htm

... are the best but more expensive. The MPPT can alter the amperage from the panel going to the battery which is discharged and at a lower voltage than the panel that is at 17 volts. Thus it sends almost the full amperage potential of the panel to the battery. The others can not increase the amperage and only hook the panel to the battery. The voltage and amperage that the panel is capable of putting out lowers until the battery voltage goes up, so even if the panel is capable of say 2.3 amps it might only be sending 2 amps (the simple answer ).

If you stay with the one 40 watt I'd go with the PWM but would switch to a 'good' MPPT controller if you add panels. That is the route we took to take full advantage of them,

Sum

Our MacGregor 26-S

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

[shanker]

Thanks Sumner. Up to 2am last night and it's becomming clearer. Maine Sail has some incredible posts out there. He seems to be the Michael Jordan of sailing

Once again your posts have explained with wonderful clarity and resources for more research. My wife says I research too much but with sailing and being a newbie, I want to do things right. From sailing etiquitte, to terminolgy, proper repair processes, to sailing techniques: there is a lot to learn. Doing things on a boat is a very different world than what I'm used to. I respect the old salts, their ways, experience and love of the water. I'll never be on their level but I'll continue to work on it. I feel like an apprentice and folks like you are my lead hands. It would be very difficult and expensive without these forums and everyones input. At the end of the day I want to be able to spend time on the water. I want to be able to bring friends and family out and have the confidence that they will be safe and enjoy their time sailing.

Well, back to work on my to do list... I will be hitting the water on the 19th!!

Shanker.

[Catigale]

Shanker - one of the distinguishing features of Mac sailors is that we dont really care about getting it all right - by far most of us are working stiffs who enjoy our boats in between the grind of work and family life.

There are really accomplished sailors on this Board, like DaveB (and not me), who are tolerant of the slack we take, yet will chime in when we are about to head off on something that really does need attention.

In short, as usual, the Admiral is right - stop worrying about getting it right, and enjoy sailing.