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Old 14-08-2015, 02:33   #1
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Solar panel controller

Hi, I just got my first real solar panel. It is 123 Watts. Do you think this is a good size for powering a decent sized electronics suite on a 28 foot boat including nonstop running of an auto pilot?

I also have two gel batteries, 100ah each, do these seem like enough? I am in a year round very sunny place.

I will probably run
Autopilot all day every day
Chart plotter alL day
Wind speed
LED lights inside and out
Charge devices from an inverter

That's about it. Is my system a good size for this?

My main question is I have to get a solar charger, I got the only one I could find somewhere in stock today, a Genusun GV-10 MPPT. It say it is ok for gels and good for up to a 140 watt panel. The reason I ask is because it is a small piece of plastic about the size of a pack of cigarettes and looks cheap. I expected a MPPT controller to look like a shore power charger, big, with lots of colorful flashing lights. Is this thing ok?
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Old 14-08-2015, 05:31   #2
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Re: Solar panel controller

I'll have a crack at answering, but I don't think I can get you all the way to a useful answer.

123 Watts is an odd size, I've never heard of that capacity on a panel, but lets assume it is accurate.

Well, working on my rule of thumb for a sunny day that you get the equivalent of 4 hours at full power, that's 500 watt hours per day. Not too shabby. Ignore the autopilot for a moment, my plotter draws about one amp with the radar off, so that's 12 watts, the instruments only draw half that (wind, depth, compass), so 18 watts, say you were running for 24 hours, that's 432 watt hours, so right there you are only JUST scraping in. But 24 hours is unlikely for anything but an ocean going yacht, so let's halve that, and I guess we are saying the basics are using half your charging capacity.


But the autopilot is a killer. What are we talking here? Tiller pilot, wheel drive motor or something on the quadrant? On a perfect day that little device is going to use more power than the plotter and instruments, and as the weather gets up it could use 10, 20 times (or more) the amount. So you will start running a deficit as soon as you start using the autopilot.

But if the boat gets to sit and recharge for a few days, like a weekender boat will, the battery capacity (100ah USEABLE between the two batteries) will cover much of this. How much...? Depends on the weather.

I guess I would say that if you have a good voltmeter, and you are not likely to get in situations where the loss of battery charge is critical, then the panel will be plenty. Certainly with our last boat, which had a raymarine tiller pilot, no plotter, a log and a few LED lights, I would have found a 123 watt panel plenty for our use, which was weekend sailing with the odd overnighter. As it was I scraped by using the battery from the car and no panel at all. I had a few pucker-up moments starting the car when I got back after a good night sail, but I never had to push.

As for the controller looking a little less than impressive... yeah, it probably doesn't look too sexy, but that's a decent brand, and when you take away the fancy displays, the heat sinks for the really big loads, buttons for klutzy fingered humans, they don't need to be big.

I bought a fancy German MPPT controller last year. Stared at the pretty lights, the fancy display, pushed the buttons, did all that for about a month, then completely and totally ignored the thing ever since. At the end of the day the fascination wears off (and I am a little embarrassed to admit how long it took for me) and all you really want is a little box that looks after the batteries while you are at the office trying to earn the $$$ to keep the boat from sinking. Only the club cat (as in the meow type) gets to see the fancy LCD display these days. I should have saved my money.

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Old 14-08-2015, 08:34   #3
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Re: Solar panel controller

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Originally Posted by northoceanbeach View Post
I got the only one I could find somewhere in stock today, a Genusun GV-10 MPPT. It say it is ok for gels and good for up to a 140 watt panel. The reason I ask is because it is a small piece of plastic about the size of a pack of cigarettes and looks cheap. I expected a MPPT controller to look like a shore power charger, big, with lots of colorful flashing lights. Is this thing ok?
Genusun controllers come highly recommended by several sources I trust. I thick you will be pleased with them.
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Old 14-08-2015, 10:28   #4
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Re: Solar panel controller

For another point of reference, we had 140W total across 2 panels, hooked into a cheapo charge controller (I don't think it was even MPPT), and we ran the following electronics while living on the hook for months at a time:
  • ST2000+ autopilot day and night while on passage. Draw from the AP was very dependent on how big the seas were and how well the sails were trimmed. Draw usually fluctuated between 0.8 and 2.5 amps if I recall correctly.
  • LED lights (drew 0.5-1.5 amps depending on how many we turned on).
  • VHF and occasionally HAM radio
  • 12V charging for tablets (we used tablets for navigation too, which is probably the biggest difference from your described system and likely led to a lower energy burden overall).
  • Fridge was an occasional luxury on sunny afternoons.
  • 12v water pump and bilge pump (occasional high draw).
  • 800W inverter for power tools (occasional high draw) and recharging AA batteries (a near constant activity while on passage to keep the sat tracker fed)

We also had 2x110AH 12V batteries, and they were adequate for the task. I added a cheapish battery monitor to our system, which I found helpful for keeping an eye on the state of charge, amount of draw, and overall battery voltage.

Occasionally we'd have a few too many cloudy days in a row and need to kick on the motor or hand steer through the dead of night to baby the batteries, but those times were relatively rare. Your biggest battery drains will occur during long passages, but it's important to consider how much of the time will actually be spent actively traveling vs. preparing for the next leg and letting your batteries recover.

All this said, I think your system would be tight on long passages but probably adequate, especially if you supplement with the engine alternator. If you don't have crew to help you take over when the batts get too low, I might err on the side of caution and nab another panel if you have the deck real estate for it. The Renogy 100W semi-flexible panels are pretty nice and compact, and I had success suspending two of them outside our lifelines near-parallel to the water.
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Old 14-08-2015, 10:45   #5
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Re: Solar panel controller

If you dont run a fridge 24/7 it might work. We use and like a Morningstar PWM controller.

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Old 14-08-2015, 11:34   #6
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Re: Solar panel controller

A 123 watt panel will provide perhaps 8 amps in full sunlight, which will translate into about 40 amp hours per day in full sunlight, assuming unobstructed (no shadows) panel. The Genasun MPPT might boost that 10% to some 44 amp hours a day.


Now sharpen a pencil and do the math, what is the load, in amp hours, of all the equipment that you plan to run, for the hours you plan to run it, every day? If it is less than 44 amp hours, your panel might suffice. Anything over about 35 amp hours, and the answer becomes "maybe".


Like all charge controllers, the Genasun comes preset for generic voltages. It may or may not match the optimum voltage for your batteries. Find out from the battery company what that voltage is, and then see if Genasun can program your controller to match it, in order to get the best long-life performance from it all. Might cost you an extra $20, not a big deal.
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Old 14-08-2015, 11:50   #7
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Re: Solar panel controller

We sell loads of Genasun GV10 controllers and couldn't recommend them more highly. Don't let the plastic case fool you that's a super advanced MPPT controller you've got.
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Old 14-08-2015, 12:23   #8
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Re: Solar panel controller

You're drawing a bit more power than you're generating in real time. But that's probably okay.

IF you are day sailing, you've got more than enough solar capacity. I have a 26' with autopilot, and my AP+plotter draw about 3 amps per hour. I have a single 100ah battery on that boat which has never drawn down in daysailing usage. With the charging bump from some motoring, you'll be generating enough power to not have to worry about it, and more importantly your boat will be charging when not in use. For daysailing, I'd increase battery capacity before I put more solar on.

HOWEVER, if you are cruising or living aboard (i.e., using the boat every day) this likely isn't enough power because you won't be generating quite as much as you're using.

It's all about your own use/duty cycle. A boat that is used on weekends could top off a 100ah battery every week with just 40 watts of panel, but a boat that's cruising would need 10X that amount to keep up with draw.
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Old 14-08-2015, 12:38   #9
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Re: Solar panel controller

Ok, good to know! I guess I should stop telling everyone about how big and awesome my solar panel is and bragging about how I could run refrigerators and everything else it's so big. Lol, I have been, that's how big it looks on the transom. This boat can't handle any more solar panels.

I'm probably sailing to Hawaii in a couple weeks and that's why I'm in a hurry to get everything done.

The autopilot is a raymarine evolution 100 tiller with a st2000 backup.

On a side note as I hook all this stuff up, my n2k cable or sea talk cables and backbone, they don't supply power to the devices do they? I still have to hook the devices up? They are just allowing them to communicate?
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Old 14-08-2015, 12:43   #10
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Re: Solar panel controller

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Originally Posted by northoceanbeach View Post
how I could run refrigerators and everything else it's so big.
You didn't last refrigeration in your initial list. Do you have it? If so, I would say your system is way undersized. You will be using over 100 ah a day most likely, and generating at most 30 ah in ideal conditions.
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Old 14-08-2015, 12:56   #11
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Re: Solar panel controller

Quote:
Originally Posted by northoceanbeach View Post
Ok, good to know! I guess I should stop telling everyone about how big and awesome my solar panel is and bragging about how I could run refrigerators and everything else it's so big. Lol, I have been, that's how big it looks on the transom. This boat can't handle any more solar panels.

I'm probably sailing to Hawaii in a couple weeks and that's why I'm in a hurry to get everything done.

The autopilot is a raymarine evolution 100 tiller with a st2000 backup.

On a side note as I hook all this stuff up, my n2k cable or sea talk cables and backbone, they don't supply power to the devices do they? I still have to hook the devices up? They are just allowing them to communicate?
If you're just installing the stock RayMarine EV-100 with the included cables, then yes, the N2K cables do supply power. The AP computer takes 12VDC directly from the battery, and then supplies power to the SeaTalkNG bus to drive the P70 control head and the 9-axis sensor.

HOWEVER! If you already have a SeaTalkNG or NMEA2000 bus that is already powered by the battery, you need to jumper the AP computer to isolate power and not provide it to the bus, otherwise you could have ground-loop issues.

Just going by memory, so check the install instructions but it does provide power over SeaTalkNG.
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Old 14-08-2015, 13:23   #12
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Re: Solar panel controller

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You didn't last refrigeration in your initial list. Do you have it? If so, I would say your system is way undersized. You will be using over 100 ah a day most likely, and generating at most 30 ah in ideal conditions.
No, I don't have it, it's just since its one of the biggest power users I use it in my joke example. Wow, I'm really surprised I don't have as much or a surplus as I thought I did, you should see the panel, it's huge!
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Old 14-08-2015, 13:23   #13
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Re: Solar panel controller

Good luck on a sail to Hawaii with your charging set up. Better have an engine with decent alternator or a Honda generator. The auto pilot will eat your batteries right quick especially sailing downwind with the large rudder excursions needed to keep the boat under control. Might find some actual experience at Single Handed Sailing Society website “Migrated from Internet Explorer” on real world feeding of auto pilots on small boats.

FWIW, Have 260 watts of solar in two panels with MPPT controller and 220 amps battery capacity in 2 6v golf cart batteries. Have a self steering vane to handle the boat under sail, all lights are LED's, run Knotmeter, Garmin 3206 plotter, and AIS 24/7. Ham radio with Pactor modem used about 3 hours a day for communication, email, and checking in with MM radio net and LED running lights at night. Sailing to Hawaii in July, had overcast for about 12 of the 15 days of the trip. By the time the sun came out, the batteries were getting down to 12v on the meter. The batteries began to charge back up with the sun but still hadn't reached full charge by the time the boat was tied up in Radio Bay, Hilo, HI.

One problem with sailing west to Hawaii is the sun is obstructed by the mast and sails in the later afternoon which cut solar production. The heavy overcast was the biggest issue, however. If you hope to make the trip on your solar charging capacity, would try and find a way to add at least one more panel and more if possible. Had a welder extend the pushpit forward on both sides so the solar panels could be mounted on the sides of the boat with pivoting mounts. May be able to do that with the life by running a suitable sized tubing over the lines and fastening the panel(s) to that. Used a nylon mount from West Systems to fasten the panels to the rail.
Didn't use the auto pilot and do not have refrigeration.
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Old 15-08-2015, 00:41   #14
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Re: Solar panel controller

If I could get a couple of flexible solar panels to mount on the cabin, because that the only way to make more fit, how do you wire them all together? Do they all go to the MPPT Genusun controller and then that goes to the batteries? Or do I need separate MPPT controllers for each solar panel?

Thanks for your help. I'll buy a Land Rover from you when I get there.
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Old 15-08-2015, 04:30   #15
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Re: Solar panel controller

Best to go separate controllers for each panel, for the least losses in partial shading. Which you will have a lot of with deck mounted panels...
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