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Old 30-05-2013, 13:29   #1
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Need help adding solar panels

Warning: I am a serious ignorant when it comes to electrical work! I have read everything I could here and elsewhere about this matter and it only made it more confusing. My electrical experience is limited to installing lights, wires, and an autopilot recently, and I barely know how to use a voltmeter. I would therefore appreciate any help that would be detailed enough and clear enough so someone like me can benefit from it (meaning: stating the obvious or explaining the basics is allowed in this thread!)

CURRENT SITUATION: 3 batteries bank, 2 house 1 start, one truecharge 20 amp (by xantrex) to monitor the charging, and one digital charge indicator reading. I can only charge from shore power or from running the engine. Everything in the boat runs on DC except for the microwave, the water heater, and the plugs (work only when plugged on shore on AC)
PROJECT:
PRIMARY GOAL: I'd like to install solar panels in order to keep my batteries charged without using shore power or running the engine, and keep it as SIMPLE as possible and autonomous (I don't want to have to plug/unplug all the time and the batteries should be able to remain topped up when I am not on the boat).
SECONDARY GOAL: I'd like to have the microwave and water heater work on DC so I do not need to be connected to shore to use them. This goal is to be considered only if it is SIMPLE.

QUESTIONS:
- Connecting the solar panels: can I connect them directly to the batteries? Or to the truecharge device? Or do I need an additional charge monitoring device or an inverter?
- Do I need 12v solar panels or 110v? If 12v, do I need an inverter to connect them to the truecharge?
- Do I need anything else?
- What is the easiest and most simple system I could implement considering what I already have?
- I was considering, after reading threads, to go for a 100w 12v renogy, and maybe add a second one later down the road. Can I do that (installing one only, and later easily "plug" a second one without modifying the whole setup)?

I am aware this is a lot of questions, I usually try to avoid that as I know it can go everywhere, but I am so lost on this subject that I couldn't narrow it down anymore. Sorry and many thanks to all contributors.
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Old 30-05-2013, 15:02   #2
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Re: Need help adding solar panels

If I understand correctly, you just want to keep the batteries charged when not using the boat and not have to plug into shore power. This can easily be done with the 100 watt panel that you mentioned.

Say you have been out overnight and your batteries are half depleted so the (approximately) 200 amp hour house batteries need 100 amps to recharge. You return to the dock but you don't run the engine long enough to do much recharging.

So you need to put back 100 amp hours by next weekend. A 100 watt panel on a sunny day will put out 30 or so amphours. So that should easily replace the 100 amphours in the house batteries.

To install this you need the panel, a place to mount it, wiring, a solar controller, and a fuse near the battery. The solar controller limits the current going to your batteries to keep from overcharging them. I won't go into MPPT controllers vs cheaper pulse width modulation controllers, but for your small needs the cheaper PWM will work fine.

You said that you may want to add a second panel, so lets size the controller for 200 watts. The maximum current that the panels will produce is approximately 200 watts divided by 17 volts (the voltage where the panel produces its maximum 200 watt rating) or 12 amps. So a 15 amp rated PWM controller such as made by Morningstar will work fine.

Wire everything with 10 gauge wire and put a 15 amp fuse near the batteries to keep from frying the wire if you get a short somewhere.

Your other question had to do with powering 110 V AC appliances- microwave etc. You can't do that directly with solar panels. So you need an inverter that converts 12 V DC to 100 V AC. BTW you don't have enough battery or solar capacity to power the water heater.

I would buy a cheap 1,500 watt Wal Mart, Auto Zone, etc inverter and use that strictly for the microwave. Place it near the microwave so that you can plug the MW into one of its outlets and wire it to the batteries with #2 wire with a 200 amp fuse at the battery.

So, that is a lot to digest. If after reading the foregoing you still feel uncomfortable, I would recommend hiring a marine electrician to do this for you. What I described above is just an outline. It takes knowledge and experience to do it safely.

David
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Old 30-05-2013, 15:25   #3
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Re: Need help adding solar panels

Simple (but you will not be able to run the microwave or water heater unless for just a few minutes)
Get 12 volt solar panels and wire them direct to the house bank.
Red to red, black to black

That's all you need.

Simple.

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Old 30-05-2013, 16:00   #4
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Re: Need help adding solar panels

what are your charging goals?.. if you have a fridge i doubt that a single 100W panel with a PWM charger will suffice, but a 130W panel with an MPPT charger should...if you dont have a fridge and its just for lighting/water pump etc.. then a 50-80W would suffice
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Old 30-05-2013, 16:01   #5
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Re: Need help adding solar panels

Trying to edit in this... But my connection is too bad...



I had 2 x 120 watt panels direct not the batteries for more than a year and it was fine. I have subsequently upgraded to a MPPT controller... But really just for the digital ammeter.
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Old 30-05-2013, 16:51   #6
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Re: Need help adding solar panels

Quote:
Originally Posted by decca View Post
- Do I need 12v solar panels or 110v? If 12v, do I need an inverter to connect them to the truecharge?

I hate to be negative, but when I got to the above I was positive that you should not be basing your work on internet advise. With that said my internet advise is that you look around your marina/anchorage/mooring field for boats with a solar panel and make friends with them, then ask their advise/experience.

Your project goals aren't that hard to achieve, don't go down some deep dark learning curve, ask for local help (a beer will go a long way).
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Old 30-05-2013, 18:04   #7
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Re: Need help adding solar panels

Thank you djmarchand for your detailed reply. For sure I'll do it myself. I know the "leave it to a professional" song by heart, but I have a very long history of (successfully) doing things that are supposed to be left to professionals or experienced DIYers without any experience at all, so this should be no exception and I'll try my luck (and gather all necessary information before starting) !

Few questions:

- Can't I just do what Mark J says? (connect it to the battery bank directly) I like this idea
- If not (why?), can't I just use the charge controller I already have instead of adding an additional layer of complexity with a dedicated solar controller? (run it through the current controller and through the existing electrical panel (so I can switch it on and off and don't need a fuse)

To Don L: I'm never short of beer and if you want to give me a hand, I'll provide! This said, I've had a different experience and came to trust forums a lot more than "dock advice", especially because you get A LOT more advices this way and can confront them openly. Forums like CF or MoyerMarine are as good as gold to me. On top of that, I just arrived in a new location (crossing from Louisiana to Tampa, FL) and know nobody so far. I just know I am not going to pay the electricity bill that comes on top of the slip fee here

Additional info: I do have a fridge, it's an adler barbour marine fridge and it draws nothing or almost nothing, despite being quite big. I hope to power it with solar. (I want to power underway: fridge, autoradio with 4 speakers, autopilot, instruments, GPS, nav lights, VHF. at the dock/mooring: fridge, autoradio, laptop, marine BTU 7000 A/C occasionally ( can forget about this if too much), microwave (I can forget about that one if it is too greedy with my electricity), GPS at mooring, water pressure, water heater, lights (x14, but not more than 4 at a time)
BTW the boat is a 30 footer and is used by 1 to 2 persons usually, used to limit their consumption of everything.
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Old 30-05-2013, 18:29   #8
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Re: Need help adding solar panels

you could get any solar panel and connect directly to your batteries (proper wire sies and fuses being used etc. etc.), it would be better to use SOME type of controller

that is as basic as it gets
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Old 30-05-2013, 18:42   #9
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Re: Need help adding solar panels

I am frequently asked "can't we just train a technician?" to do a job that a chemist or engineer would ordinarily do. Well, yes, we could. In fact, I didn't know how to do the job when I came out of high school either. Training for a lab chemist...

  • will take 4-5 years in a university and
  • there will be a substantial cost
It's kind of like that with electricity and many things. No, it is not so simple and some understanding of electricity is needed unless you want to burn your boat down (no mention of fusing for starters) or fry the batteries (yup, you need a regulator unless the panel is VERY small).

There are some great books on boat wiring. Read one cover-to-cover. If that sounds like a drag, boring, then this is not for you. Don't do it just to save a few bucks; mistakes are really expensive (a new battery bank would be a best-case failure).

I posted this:
http://sail-delmarva.blogspot.com/20...ar-panels.html

But I left a lot out.
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Old 30-05-2013, 19:34   #10
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Re: Need help adding solar panels

Hello Decca! I think that you should really hire a marine electrician to do the work you need. While the electrical work may sound easy to do, there is a lot knowledge that goes behind it. You mentioned that you do not own or know how to use a DMM (Digital Multi Meter - Voltmeter/Ammeter), how are you going to check your work? Another thing to consider is insurance coverage on your boat. Unless your work is checked by a licensed electrician, in case of an electrical fire...you'll be in a very bad position in defending yourself. I really recommend you to get a professional to do your electrical work; it's a free advice, take it! Mauritz <Electrical Engineer>
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Old 30-05-2013, 19:39   #11
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Re: Need help adding solar panels

The larger your panels and the smaller your battery banks, the more you'll need a regulator/charge controller. This will keep you from overcharging the batteries.

One thing that will help you design your system is an energy budget. Do you run a refrigerator? If so, how many amp-hours per day does it draw? On my boat, I know I need somewhere around 100 amp-hours per day to keep it happy when I'm on the hook, and more when I'm sailing.

I agree with Markj that you should forget about the secondary goals mentioned in your original post. Inverter systems are just too inefficient for that. Running the water heater off solar just isn't an option for most sailboats. We can run our microwave for a few minutes here and there with our system, but I hate doing it because of how it sucks down the amps. It's real easy to suck down an hour's worth of charging time in just a few minutes.

One of the reasons folks are suggesting you get help is that your original post asks whether you should get 12v or 110v panels. This suggests you may not understand the difference between AC and DC systems. If that's the case, you really aren't ready to design your own system. (No matter what panels you got, btw, they'll only put out DC.)
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