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Old 25-03-2011, 08:37   #16
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Re: Solar Panel, too big?

teneicm,

MPPT controllers are the brains of the Solar panel system.
Once you set it up, the controller handles everything, even battery temp.
You know how good your system is when you forget about it and you just always have full batteries.
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Old 25-03-2011, 08:40   #17
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Re: Solar Panel, too big?

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Originally Posted by teneicm View Post
So do most MPPT controllers account for overcharge situations? What happens if the batteries are fully charged but the solar panel is still putting out amps?
Unlike a wind genny, a solar panel only makes power with a load applied. No need to "dump" power after the controller senses the batts are full.
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Old 25-03-2011, 10:52   #18
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Re: Solar Panel, too big?

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Originally Posted by Velocir View Post
Can anyone give me a quick rundown on the different types of regulators/charge controllers? MPPT As opposed to?

MPPT regulators convert energy from the solar panel differently from convention regulators. The aim is to extract more energy from the panel that would otherwise occur . The manufactures claims have been summarised by Cotemar.

However I feel the real world improvement in boat solar systems is much less than these claims.
MPPT regulators are useful if you want to use panels designed for higher voltage than your batteries (24v panels in a 12v system for example).
As far as the batteries are concerned MPPT regulators and conventional regulators behave the same. Generally you are far better, if possible, to spend your money on more solar watts
Be wary of cheap MPPT regulators the performance can be poor.
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Old 25-03-2011, 11:26   #19
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Re: Solar Panel, too big?

JUST GO GET A BLUESKY 20 MP CONTROLLER/REGULATOR AND GO AWAY WITH A BIGASS SMILE AS YOU WILL HAVE PLENTY OF POWAAAHHH AND NOT HAVE TO RELY ON MANY MANY MANY ADDED PANELS AND COMPETITIVE SYSTEMS TO V=CHARGE YOYUR BATTERIES, ;HAVE FUN AND SMOOTH SAILING
BTWW--THE 20 AMP REGUALTORS ARE WONDERFUL--HAVE HAD ONE FOR OVER 5 YRS WITH EXCELLENT RESULTS. EVEN TOOK IT FROM MY ERICSON TO USE INMY FORMOSA AS IT IS SOO GOOD.
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Old 25-03-2011, 12:19   #20
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Re: Solar Panel, too big?

An MPPT controller will take higher voltages and regulate them down to the lower voltages needed for battery charging. In the case of two similar panels, you can wire them in series for 24v plus voltage so you can either use smaller feed lines and/or have less line loss to the controller. The controller will automatically go into a float charging state when the batteries are fully charged so no need to worry about having too much charging capacity. For those who haven't checked your panels output, a nominal 12v panel will generate way more than 12v in bright sunlight. MPPT controllers convert higher voltages, I'd guess closer to 40 volts in optimum conditions, into charging voltages for batteries which is about 14.2 volts give or take a few tenths. Don't know whether you'd need a special MPPT controller to handle more than 24v nominal out put if you wired more than two panels in series. MPPT work with nominal 12v input as well, they just lose some of the efficiency that you are paying dearly for.

Realestate for mounting panels is a problem on most boats. On my boat, I had a welder extend the Pushpit top rail about 2', added another vertical support and cross bracing to mount a 135 watt Kyocera panel each side. The panels are wired in series for a nominal 24v into an MPPT controller. I thought this would be overkill for my relatively small needs, no refrigeration, TV, all LED lights, self steering vane, etc. When the sun shines they do produce way more juice than I need but the pesky sun don't always shine. Any shading drastically reduces the output of a solar panel. Even a slight haze can reduce the output by 1/2 and an overcast by 80% or more. Forget getting any charge from a full moon. Also, you have to be cognizant of stuff on the boat that will shade the panels. Mounting the panels on a bimini or dodger with a boom overhead will significantly decrease output unless the boom is swung out of the way. Mounting the panels as high and as far aft is the best but still has some issues. On my recent TransPac, I was heading into the afternoon sun the whole way. After about 1400, the mast and Mainsail began to shade and totally shading the panels by about 1600 which resulted in a significant reduction in total daily output. Also, I was on Port tack with prevailing easterly winds for about half the distance so boat and panels were heeled away from the sun reducing their output.

On my summer slide to Hawaii had heavy overcast for almost half the trip. After about 10 days, my 220amp house battery bank was getting below 12v and needing charging even with my limited need for juice. Underway, I run a Garmin 3206 plotter, AIS, and knotmeter all the time, intermittant use of Ham Radio, Pactor Modem and Netbook Computer and LED running and interior lights when the sun goes down. Overall usage is probably less than 3 amps per hour overall. Still, that's almost 70 amps a day if my calculations are correct. Enough load to drain my battery bank in a few days without charging. My 270 watts of maximum possible solar output really helped but didn't keep up with the daily usage in overcast conditions. Once the sun finally came out, the batteries slowly recharged so I didn't have to run the engine to charge the batteries on the 15 day passage. For those with refrigeration, an autopilot, and a crew that needs constant visual and aural stimulation, way more generating capacity is going to be needed.

Beware of efficiency claims for panels. FWIU there are two types of panels. The higher efficiency panels are not shade tolerant. Otherwise they are more effected when not pointed directly at the sun in clear sky conditions. Other types of panels are not as ultimately efficient but more tolerant of less than perfect conditions. Overall, the one type is better for the less than perfect conditions on a boat. This is what I've heard so if I'm wrong on this, hopfully others will correct me.

So in your case, put on as large and/or as many panels as you can fit if solar is going to be your only non fossil fuel charging source. Putting a 200+ watt panel on your stern may be the best way to go. The one you are looking at has a high enough voltage so it should make good use of the greater charging efficiency of an MPPT controller. If you can stow additional panels to supplement your output at anchor, all the better. On a 27' boat, stowage is at a premium, however.

The best way to become energy self sufficient is to cut the amount of amps you need. We lived aboard and cruised for nearly 4 years without refrigeration and don't have it on my current boat. We didn't/don't miss it. Amazing how much better food tastes at room temp, even beer. Most food will keep for several days without refrigeration even in the tropics.

Some form of self steering is mandatory on a cruising boat. An autopilot will draw a tremendous number of amps in the real world of sailing a boat on the open ocean. You'll not only need to buy the autopilot but all the spares for the inevitable breakdown, the increased battery bank to handle the load, and generating capacity to feed the hungry bastard its electrons. In short the real cost of an autopilot for an offshore sailed boat is way more than twice the initial cost of the pilot. A self steering vane works for free and will steer the boat for about 99% of your cruising time. It also is a fairly simple mechanical device that can be fixed with a little chewing gum and duct tape by the average sailor should anything go wrong. Contrast that with an autopilot that requires an EE degree just to read to read the manual. TV's, DVD players and Muzak piped throughout the boat are trappings of our modern society. We've managed to do fine, thankyou, without that external stimulation. Somehow I'm never been bored on the boat and don't have that niggling desire for more 'stuff' to occupy my time. Of course, that's the need for more stuff that doesn't have to do with sailing the boat.

Sounds like you have a good plan for installing solar on your boat. It's certainly made my boat way more pleasant not having to run the engine at all.
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Old 25-03-2011, 12:52   #21
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Re: Solar Panel, too big?

I have 2 50 watt panels on our 34' boat, about 2' square, it's plenty. try Kyocera, they make a heavy frame panel.
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Old 25-03-2011, 12:55   #22
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Re: Solar Panel, too big?

Quote:
Originally Posted by roverhi View Post
For those who haven't checked your panels output, a nominal 12v panel will generate way more than 12v in bright sunlight. MPPT controllers convert higher voltages, I'd guess closer to 40 volts in optimum conditions, into charging voltages for batteries which is about 14.2 volts give or take a few tenths..
The guess of 40V is a long way out I am afraid.
The typical specifications for a 12V solar panel give a voltage about 17-18V at load. One problem that these specifications are for a cell temperature of 25C (77F) .Solar cells rapidly heat up and cell temperatures are much higher than this in practice. (they a measured with brief flashes of light to keep to this temperature) The voltage goes down with an increase in cell temperature.
The addition problem on a boat is even a slight shadow (or overcast conditions) will drop the voltage further so most solar cells on boats are generally operating only slightly above the maximum battery voltage.
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Old 25-03-2011, 17:03   #23
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Re: Solar Panel, too big?

Thank you for all your help Pete. We have all led lights and have no refrigeration, so I think you are right about going with 2 smaller solar panels and I will look more into the controllers your recommended.
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Old 25-03-2011, 18:24   #24
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Re: Solar Panel, too big?

We got one of these along with a BlueSky controller and like them very much:

Solar Cell, Solar Panel, Solar PV, Solar Products, Charge Controllers, Solar Trackers
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Old 25-03-2011, 19:10   #25
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Here's my set up

2 x 150 watt Panels 37 Voc
Wire parallel into a
Morning Star MPPT 24v to 12V 15 amp controller
Through fuse block to 350AH House Batteries. Start battery charge maintained by
BlueSea 120 amp Combiner

Monitors & Controllers
Left hand - Wind controller & Monitor recycled 10 amp solar controller with combiner indication
Center - Xantrex Linc 20
Right hand - Morningstar remote panel. At time of picture remote panel is indicating 34.22 volts from panels

I love green lights!
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Old 25-03-2011, 19:56   #26
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Re: Solar Panel, too big?

Hi my boat has 2 panels, a 50 watt and an 80 watt through a morningstar sunseeker duo controller, charges both battery banks independently and provides all the power I require for instruments, autopilot, refrigeration and entertainment when required. I couldn't be happier with the system. Cheers
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Old 31-03-2011, 23:02   #27
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Re: Solar Panel, too big?

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Originally Posted by Velocir View Post
I am trying to wrap my head around solar charging systems. I have a 27ft pocket cruiser and my plan is to build a removable arch on top the stern push and mount a solar panel there.
What I can't seem to figure out is will this (Sharp NU-U235F1 - Sharp NU-U235F1 235 Watt Solar Module) 20v 235 watt solar panel work with a charge controller on our dual bank deep cycle system?
It's a whole new language, amigo!

There is a long and informative thread here:

Solar Enough ?

I'm opting for stern davits with a 200W panel and a 15A MPPT charge controller. The 15A CC might limit my total charge on a really great solar day, but I'll get all available power on the average to marginal days. I'm looking at this panel for $368 ($1.84/watt)

Suntech Solar Panel 200 Watts 26.20 Vmp [STP200-18/UB-1 A-1] - $368.00 : Solar Panels, Inverters and PV Systems | Worlds Lowest Price, Powered by Nature!

and this controller for $199

Morningstar Corporation » SunSaver MPPT

This is about as low cost a system as I can find. If you can do better for 200W, please let me know. We sub-30' guys need to look out for one another.

John
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Old 20-11-2011, 09:40   #28
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Re: Solar Panel: Too Big?

I had read somewhere that the MPPT yields its best return when the panels are wired in series. I finally reached a techy at Blue Sky who helped me through the muck of data and claims. Most solar systems are aimed at the mass market of home and commercial users. Marine presents different demands other than salt. We want highest density panels for least space available. We also need to charge even in non-optimum conditions. An MPPT controller is a variation on a pulse width (PWM) charge controller. It can modify the input voltage & power to the best profile to charge your battery system. It can, however, only reduce voltage from input. This means that if you want to charge in partial shade or rising/setting sun you must put your panels in series. The impact to the us is that we need to use an MPPT with a high input voltage capability. Also panels need to preferably be identical. Once you have selected your panels, add the open circuit voltage for the maximum series voltage of the combined panels. The MPPT needs to be capable of at least that input voltage. The rub is that most MPPT units are only rated to 45 to 55 VDC. Blue Sky has the only maker I have so far found that has a unit with a high voltage input rating. (120 volts DC). Two or three panels in series will typically be around 90 to 100 VDC. For my 24 VDC battery system, (28.7 volts charging) I will be able to charge as long as the series voltage is above this minimum. I will be using a Blue Sky 3048DL. 12 volt systems and dfferent power ratings/panels will effect the MPPT selection. I suggest that you call them and confirm the best MPPT selection before you buy.
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Old 20-11-2011, 10:01   #29
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Re: Solar Panel: Too Big?

We have 660W solar power and this is more than enough for a freezer and 2 fridges (all 6 cu.ft.ish), navlights at night and autopilot 24h/day.

However, it's not enough for the crew. Just turning up the rock music a bit already takes over 100W just for that. Think microwaves, computers, water maker etc.

We need a genset in addition to the solar panels and don't mind that at all because it also provides an hour of A/C and hot water every day while charging the batteries and running the 240V water maker.

ciao!
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Old 20-11-2011, 10:06   #30
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Re: Solar Panel: Too Big?

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The rub is that most MPPT units are only rated to 45 to 55 VDC. Blue Sky has the only maker I have so far found that has a unit with a high voltage input rating. (120 volts DC). Two or three panels in series will typically be around 90 to 100 VDC. For my 24 VDC battery system, (28.7 volts charging) I will be able to charge as long as the series voltage is above this minimum. I will be using a Blue Sky 3048DL. 12 volt systems and dfferent power ratings/panels will effect the MPPT selection. I suggest that you call them and confirm the best MPPT selection before you buy.
The re are a lot of MPPT regulators that will handle these higher voltages.
Models from Outback, Midnite, Xantrex and others, are OK with around 150V DC.

The need for high voltages is however only seen in very large domestic arrays where the high voltage is needed to prevent wire loss.

There has been a lot of debate about series or parallel connection for a boat, but IMHO if you do connect the panels in series I would not look at connecting more than 2, nominally 12v panels, in series for a 12v battery.

Be careful about the risk of lethal shocks if you wire a lot of panels in series.
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