Installing one solar panel to two batteries

[northoceanbeach]

I'm sorry to start a new thread, I just wanted to keep this one straight to the point.

I bought a single large solar panel. It has a box on one side for the wire to attach. I am now reading the instructions and it is confusing, but I think like a lot of projects, I just don't understand at first.

I thought I just attach wires to the solar box, on red and one black, that came supplied to the mppt. It has one side for from panel with two slots, Pos and neg and two out to batteries.

Maybe it is that simple. I am reading the instructions and it says

"Each photovoltaic module has a hole in the side of he frame for either a bolt, but and washer grounding the the module,to the frame or an appropriate screw, hardware not provided. An example of nut and washer is shown in figure 12. In a connection of this type the star washer must score the frame to make possituve electrical contact"

What are they talking about? Am I supposed to do more than connecting to batteries? I can't imagine wires hanging all over the solar panel. All up and down the sides.

Second. I have the standard red switch for my batteries, off, one, two both, and my batteries and linked with a black thick wire. When I do attach the mppt controller, do I hook it to one battery and since they are linked it will power both or do I need to connect to each battery individually, thanks for the help.

[Dsanduril]

Originally Posted by northoceanbeach

...What are they talking about? Am I supposed to do more than connecting to batteries?

I hesitated to respond to this thread, because there is a whole book that needs to be written (and read) in response. For the short version, which is by no means comprehensive...

They're talking about a safety ground for the module frame. On the chance that the electrical wiring gets shorted to the frame (through some damage to the module or wiring) it is recommended to have the module frame grounded so that someone that touches the module doesn't electrocute themselves. This is usually done by grounding the module to the mounting rack, then grounding the mounting rack to the system ground (on a boat that is probably, but not always, the engine block). This will not affect module operation, only safety. You only need one connection from the module frame to the mounting system, and one from there to your system ground.

The easiest solution to your other question is to connect your MPPT to the OUT of your 1-2-both switch, that way you will be charging the battery you are using. If you have the switch on both then you will charge both, if you have it on 1 or 2 then that is what you will be charging (and if you turn it off you won't be charging anything). There are lots and lots of reasons to make it more complicated than that, and to connect separately, and to install a different switch for the charging system, but that is the simplest way.

[northoceanbeach]

Thanks, I am making lots! Of progress since I wrote that first post. I hooked a voltmeter up to the solar panel and am reading 20.36 volts being produced with the late afternoon sun.

I'm ready to wire it. Where is the out on my one two both switch? I see it has a big red cable coming to each battery possituve, other than that everything is hidden.

Thanks so much for your help.

[smac999]

idealing one battery is stating and one is house. and there is only the need charge the house, so it goes direct to there. I wouldn't put it to the switch output.

[northoceanbeach]

It's coming along well. Done for the night. I have the panel hooked into the mppt controller and ready to take the next step tomorrow.

Do I need any inline fuses anywhere? Thanks for he help, I was at a stumbling block earlier but am progressing now!

[newhaul]

When you hook everything up start by hooking straight from the house battery to the controller then hook up the panels to the controller. Doing it the other way ( starting at the panels ) may damage the charge controller also when disconnecting do the opposite panels first then disconnect battery don't wire it via the battery switch. IIRC

[northoceanbeach]

Ok, for tonight at the end I did what you said not to do which is connect the panel to the charge controller first. Hopefully no damage but I didn't hook it to the batteries and there was also very little light left.

Is it safe to leave it attached to the controller if I don't get to it tomorow?

Is it safe to work on tomorrow since it will be very sunny and these wires are now hooked up to the panel. Can I touch the ends or will I get shocked? I didnt even think about that until just now.

So I'm almost there I just need to know:
1: safety: since it's not connected, I can change anything tonight while it's dark.

2: where to hook the wires from the mppt to, to supply power to the batteries evenly

3: any inline fuses or anything else? That can be done tonight. I can cut and splice anything I need to do tonight.

[newhaul]

OK first to dispell some minor misinformation you are talking under 24 volts so won't shock you ( grab both posts on a car battery what happens to you). Disconnect the positive wire from the controller to panel at the controller. Wire from the panel to the house battery positive post with a fuse in line and the ground to the system ground. Then rehook the positive wire from the panels to the controller. You are now all hooked up and charging.

[northoceanbeach]

So you are saying.

Disconnect possitive wire from panel to controller.

Add inline fuse in possitive wire from controller to house battery.

Connect wire with inline fuse from controller to house battery.

Connect black wire(negative) from controller to my engine block or other ground.

Reconnect possitive wire from panel to controller.

---this will leave me looking like. Red and black wires connected to possitive and negative on panel. Connect to possitive and negative at controller.

Possitive red wire from possitive at controller wired to house battery possitive terminal with inline fuse. Negative black wire from controller to some ground on boat.

---so this will allow me to charge both batteries with the solar panel depending on switch position? Even though I am only hooked up to house battery I can still flip the switch to only starter battery and charge that?

The negative wire from the controller doesn't go to the negative terminal on my battery?

What size fuse should be inline? 15?

Thanks for holding my hand through this. I am learning a lot and am very appreciative.

[newhaul]

Yes that sounds right and yes you can go to the ground on the battery I just prefer to ground to the main ground buss for the system and a 15 amp fuse will be OK depending on size of panel go about 1.5 times the open amp output for fusing. The last is yes you will charge the main house battery all the time and can add load the other battery via the switch with constant charging life,e solar I usually leave the switch to charge them both all the time

[Dsanduril]

When you are installing a fuse it should be installed at the battery end. Ideally within 6 inches of the battery. In a solar system the panel cannot create an overcurrent situation, solar panels are current limited by their nature. But if you cable direct to the battery, and that cable ever gets damaged, their is a very real chance that the entire battery can discharge at once through the small cable you have connected to your MPPT. Thus the fuse is to protect against overcurrent from the battery, not from the solar panel/MPPT. The length of the cable from the battery to the fuse is unprotected, so the shorter that length the better.

Anywhere you connect (#1 battery, #2 battery, switch OUT) will charge both batteries if your switch is in the BOTH position. The BOTH position joins everything together and for electrical purposes you now have one big battery, so charging current will find its way around the circuit.

[Stu Jackson]

Originally Posted by Dsanduril

Anywhere you connect (#1 battery, #2 battery, switch OUT) will charge both batteries if your switch is in the BOTH position. The BOTH position joins everything together and for electrical purposes you now have one big battery, so charging current will find its way around the circuit.

Good advice on wiring & fuses.

Another way to say this is that the OP appears to need to understand how a basic 1-2-B switch works.

There are four POSITIONS on each switch: 1, 2, B and Off.

There are three POSTS on the back of the switch: 1 from battery 1, 2 from battery 2 and C, the Common post.

The C post is the one that connects the starter and the main electrical panel. The current flows from the selected battery and then OUT to the "users" of the power. This term is "a USE switch."

Most often, in OEM boat wiring, the C post also is connected to the alternator output (AO), so it becomes the determinant for what battery gets charged. This term is "A charging switch."

Modern electrical system design removes the AO from the C post of the battery and moves it directly to the house bank. This then makes it ONLY "A USE switch."

The advantage is that even if the switch is turned off with the engine running no damage will occur at the alternator diodes because there is always a connection, directly, from the AO to a battery.

Here's a longer discussion and two other basic wiring design posts:

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

Don't feel bad, most new skippers don't understand this either.

Good luck.

[chiefcoxswain]

Good advice Stu.

[northoceanbeach]

Very good advice all.

[northoceanbeach]

So I'm hooking this up. The wires are reading they are getting power. The re battery switch connect the batteries when in both position so I can just hook my solar controller to the house battery and when I want solar to charge both, switch it to both.

Why then is my shore power charger hooked to both batteries instead of just the house?

Sorry I'm so annoying. I've just got this last thing to do and I've been doig a lot and I really just want to hook it up and it works and not have more works on my hands.