Solar Sailboat System; Seeking Advice

s/v alpha wave

Hello All -

Your site has been invaluable in helping me think through a new solar installation on my live-aboard sailboat (40-foot sloop) cruising the Caribbean. I have a few questions I'd like the community's comments on.

My objective is to replace, through solar, as much of my power consumption as possible while I'm at anchor, in order to minimize engine run time/frequency for charging.

My QUESTIONS ARE IN ALL CAPS down in the "Proposed Installation" section. I apologize in advance for the lengthy post; it seemed more efficient to give all the pertinent information in the first post. Plus, I'm on the verge of placing orders, and I'd like to move quickly. I would appreciate any insights you can share.

First, the current configuration:

Power system:
~ House battery bank, 3 x 8D gels in parallel, for a 675 Amp hours @ 12 V bank -- batteries are old (10yrs?) but have spent almost entire life in float charge status in a slip, seem to be doing fine, but when they fail, will be replaced by AGMs;
~ Starter battery, 1 x Group 31 AGM, 105 Ah @ 12 V -- 1 yr old replacing a flooded G31 that came with the boat and worked just fine, but the insurance surveyor insisted that the battery be leakproof;
~ Engine charging: 90 Amp alternator feeding house bank through Xantrex Smart Regulator;
~ Starting battery charged by Xantrex Echo Charger from house bank feed;
~ Shore power when in marina: 30 Amp service fed into Heart 2000 charger/inverter to house bank;
~ System Monitoring: Heart Interface Link 2000R

Loads:
~ Net consumption at anchor, averaged about 120 Ah/24hrs last winter in Bahamas;
~ Boat has had extensive refit, with focus on power conservation -- running lights and cabin lights all LED, refrigeration insulation doubled and efficient "smart controller" / keel cooler system installed, etc;
~ Can't easily isolate individual loads, but biggest consumer certainly refrigeration, estimated 45-70 Ah/day, fairly sensitive to ambient and water temperatures, second biggest consumer probably computer/long distance wifi system (room for improvement here if I break my shore-side habit of leaving it on all the time);
~ Almost all loads run off the DC circuits directly, including computers/wifi, only rare use of inverter at anchor for power tool or quick reheat in microwave;
~ Only new load planned is a single sideband radio and Pactor modem, to enable email from anywhere, might draw additional 10-15 Ah/day when no shore-based wifi available.

Site for solar panels:
~ Only appropriate space is atop the bimini (the shade cover for the aft part of the cockpit). The bimini was designed and built to be able to provide support for solar panels.
~ Slight shading is inevitable, as the backstay rises at a steep angle to the top of the mast through the center of the bimini -- the backstay is a one-quarter inch diameter steel rod, and will put some kind of shadow on one or the other of the panels under virtually all sun angles, but never both at the same time;
~ Bimini is supported by a framework of one-inch diameter stainless steel tubing, which is being reinforced to prevent any movement under the additional weight and windage;
~ The panels will be supported by two transverse crossbars, which will have a two-inch crown (an even, shallow upward curve from one side to the other, to strengthen the long dimension of the crossbar to support the weight of the panels) -- this gives a 1:20 slope to the panels for drainage, but the outside edges of the panels could be shimmed up level if this slope is not appropriate;
~ The area that can be filled by the panels will accommodate a maximum of 40" x 66" panel size, one on either side of the backstay;
~ It is physically possible to mount a similar-sized panel over the dinghy davits aft of the transom, but this is very undesirable due to interfering with boarding via the stern ladder (the normal access to the boat when at anchor), and due to adding excess weight aft of the transom, which has negative effects on handling. However, if I eventually decide to take the boat into the South Pacific, I might reluctantly add a third panel here.

Proposed installation and questions:
~ Panels:
I looked hard for a way to put 4 smaller panels in the same space (to minimize the impact of shading), but found nothing in appropriate dimensions to achieve anything near the same total wattage with four panels. I've identified three full-sized panels as candidates (among highest wattage in 40" x 66" format):
>Kyocera KD245GX-LPB ( 245W; Vmp=29.8 ; Imp=8.23 ; Voc=36.9 ; Isc=8.91 )
>Solar World SunModule 255 ( 255W; Vmp=31.4 ; Imp=8.15 ; Voc=37.8 ; Isc=8.66 )
>Yingli Panda Series 260 ( 260W; Vmp=30.8 ; Imp=8.46 ; Voc=38.6 ; Isc=8.91 )
The pair of panels would be wired in parallel because of the shading issues.

QUESTIONS ON PANELS:
ANY REASON TO PREFER/REJECT ANY OF THESE? ANY OTHERS I SHOULD CONSIDER? GIVEN MY OBJECTIVE OF MAXIMIZING OUTPUT, IS THE DIFFERENCE OF 30W (490W vs. 520W) ENOUGH TO CARE ABOUT AS A PRACTICAL MATTER? For what it's worth, the sailing community has historically been partial to Kyoceras, seemingly because of warranty support and construction quality.

~ Charge Controller:
My readings of product specs have inclined me towards the Morningstar MPPT-60 -- it has the capacity to add a third panel if eventually necessary (the MS MPPT-45 will not handle a third panel in these sizes, according to Morningstar's online "configurator") and the MPPT-60 would give a web-accessible readout of status and performance, which the MPPT-45 lacks. The web-based data access would permit me to rely on the existing Heart Link 2000R monitor for general system status, as opposed to buying an additional controller-specific monitor.

QUESTIONS FOR CHARGE CONTROLLER:
IS THIS AN APPROPRIATE CHOICE OF CONTROLLER FOR RELIABILITY AND EFFICIENCY? IF I SHOULD BE CONSIDERING OTHER CONTROLLERS, WHICH SHOULD BE CONSIDERED? ARE THERE KNOWN RADIO INTERFERENCE ISSUES WITH THIS OR OTHER SUGGESTED CONTROLLERS? WOULD IT BE WISER TO PURCHASE THE CONTROLLER-SPECIFIC MONITOR AS WELL?

~ Relationship between the battery bank and the panels' charging capacity:
I've read many of the forum's posts about the required power levels necessary for charging different-sized battery banks. I get the basic issues, but am having trouble understanding the consequences of deviation from the guidelines.
>My current house bank is 3 x 8D gel, with 675 Ah capacity. The future replacement would be AGM, with 750 Ah capacity. These sizes are pretty appropriate to meeting the "days-without-sun" criterion of two to three days capacity before hitting 50% State of Charge.
>However, maxing out the panel power in the space available gives me charging current of less than 5% of bank capacity. For the current gel batteries, using a wattage derating of 0.77 and a charging voltage of 14.4 gives a rate of 3.8% with the 245W panels and 4.1% for the 260W panels; similarly, for the future AGM battery bank, using a charging rate of 14.1 volts, the 245W panels charge at 3.6% and the 260W panels charge at 3.8% of capacity.
>The only way to get the charging rate above 5% would be to reduce the house bank to two AGM 8D batteries for a total capcity of 500 Ah or add a third panel, both of which are unattractive options. With a 500 Ah bank of AGMs, the charge as a percent of capacity would rise to 5.4% and 5.7% for the 245W and 260W panels, respectively. But it would be at the cost of reduced "days-without-sun" capacity, and perhaps problems when you need the extra reserve. For example, one would normally draw down the bank to 50% SOC on the morning you expected to leave for another harbor, and then need to run the anchor windlass, a 1200W motor.

QUESTIONS ON CHARGING CAPACITY:
WHAT IS THE PRACTICAL CONSEQUENCE OF CHARGING RATES BELOW 5% OF BANK CAPACITY -- IS IT SIMPLY SLOWER, OR LESS EFFICIENT, OR DOES IT DAMAGE THE BATTERIES SOMEHOW? HOW CRITICAL IS THE 5% LOWER LIMIT -- IF I STRUCTURE THIS SO THAT THE MAX CHARGING CURRENT IS ONLY 3.6-3.8% FOR THE FUTURE AGM BANK, IS THAT A RECIPE FOR DISASTER (OR DISSATISFACTION)? DO I ABSOLUTELY NEED TO DROP THE FUTURE AGM BANK DOWN TO TWO 8Ds FOR 500 Ah IN ORDER TO ACHIEVE A CHARGING CURRENT OVER 5%? ALTERNATIVELY, IS IT IMPERATIVE TO START OUT WITH THREE OF THESE PANELS ON THE LARGER BANK?

~ How best to cycle the battery's state of charge:
>I assume that the solar array output will fall short of consumption. As an example, let's say it falls short by an average of 15 Ah per day on the average, or about 2.5% of bank capacity in the case of the 675 Ah bank of gels. A charge cycling strategy would have lower and upper bounds (SOC low limit of what? 50%? 75? and an SOC upper limit of 80%? 90%?) plus a rule for how frequently the SOC must be pushed to 100% or above. As I understand this, the lower limit has implications for battery longevity, and the upper limit has implications for charging efficiency. The necessity for the rule about intermittent charges to 100% and/or equalization has to do with avoiding permanent sulfation, but I don't understand how to apply it to gel and AGM batteries.
>Obviously, the battery's acceptance curve relative to SOC is an important factor in how much you are able to take advantage of the solar panels' potential to produce power. In this hypothetical example, one might cycle between SOC 50% and 80%, lasting about 12 days on solar alone before running the engine to come back that 30% of capacity (perhaps 4 hrs run time). Or, if one chose 75% as the lower limit and 90% as the upper, you could live off solar for six days, then run the engine to restore the 15% of capacity (from 75% back up to 90% SOC), but you might have to run the engine 3 hours because you would be in a less favorable part of the acceptance curve.

QUESTIONS ABOUT HOW TO CYCLE THE BATTERY'S SOC:
IS THERE ANY WAY TO QUANTIFY (OR EVEN JUST JUDGE BY SOME RULE OF THUMB) THE LONGEVITY/EFFICIENCY TRADEOFFS? IS THERE A "SWEET SPOT" ALONG THE ACCEPTANCE CURVE WHERE YOU GET YOUR BEST VALUE OUT OF YOUR SOLAR CAPACITY? WHAT WOULD YOU RECOMMEND FOR A STRATEGY FOR CYCLING THE SOC? HOW DOES THE SULFATION ISSUE APPLY TO GEL AND AGM BATTERIES? DOES ONE NEED TO EQUALIZE? HOW FREQUENTLY SHOULD ONE ACHIEVE A 100% SOC? IS THERE A BIG DIFFERENCE AMONG BRANDS OF BATTERIES IN TERMS OF SETTING A CYCLING STRATEGY? IS THERE AN OVERALL RECOMMENDATION FOR A MANUFACTURER OF AGM BATTERIES?

Many thanks for your patience with what has turned into a mammoth post. I look forward to hearing your advice.

S/V Alpha Wave
1985 Nordic 40 Sloop

niel

Re: Solar Sailboat System; Seeking Advice

welcome to the forum.

"QUESTIONS ON PANELS:
ANY REASON TO PREFER/REJECT ANY OF THESE? ANY OTHERS I SHOULD CONSIDER? GIVEN MY OBJECTIVE OF MAXIMIZING OUTPUT, IS THE DIFFERENCE OF 30W (490W vs. 520W) ENOUGH TO CARE ABOUT AS A PRACTICAL MATTER?"

in general i wouldn't worry too much over minor power differences, but as you know the more you get the better.

"QUESTIONS FOR CHARGE CONTROLLER:
IS THIS AN APPROPRIATE CHOICE OF CONTROLLER FOR RELIABILITY AND EFFICIENCY? IF I SHOULD BE CONSIDERING OTHER CONTROLLERS, WHICH SHOULD BE CONSIDERED? ARE THERE KNOWN RADIO INTERFERENCE ISSUES WITH THIS OR OTHER SUGGESTED CONTROLLERS? WOULD IT BE WISER TO PURCHASE THE CONTROLLER-SPECIFIC MONITOR AS WELL?"

any good quality mppt controller is fine and note that any of them could put a spike right where you want to operate. only 2 are certified for low emissions and that's the midnite classic and the xantrex mppt60. the tristar may work fine for you too, but it all depends as one may have a certified cc that may put a spike at say s7 where you want to operate and the non certified cc may not have a spike where you want to operate and may throw a s9+15db signal just outside your place of operations somewhere. do look into the midnite classic controller though as it can handle far more current and is feature packed, but at a slightly higher price. a monitor may help you track battery soc, but it may have a degree of innacuracy too.

"QUESTIONS ON CHARGING CAPACITY:
WHAT IS THE PRACTICAL CONSEQUENCE OF CHARGING RATES BELOW 5% OF BANK CAPACITY -- IS IT SIMPLY SLOWER, OR LESS EFFICIENT, OR DOES IT DAMAGE THE BATTERIES SOMEHOW? HOW CRITICAL IS THE 5% LOWER LIMIT -- IF I STRUCTURE THIS SO THAT THE MAX CHARGING CURRENT IS ONLY 3.6-3.8% FOR THE FUTURE AGM BANK, IS THAT A RECIPE FOR DISASTER (OR DISSATISFACTION)? DO I ABSOLUTELY NEED TO DROP THE FUTURE AGM BANK DOWN TO TWO 8Ds FOR 500 Ah IN ORDER TO ACHIEVE A CHARGING CURRENT OVER 5%? ALTERNATIVELY, IS IT IMPERATIVE TO START OUT WITH THREE OF THESE PANELS ON THE LARGER BANK?"

we like to recommend charging between 5% and 13%, but understand this is not in stone either. batteries have a self discharge rate and you have to charge above that and it would be excruciatingly slow to charge, but would put something into the batteries. gels are a bit touchier to charge with voltage and current constraints on them and i have to say i am unfamiliar with their charge efficiencies to properly comment on them. agms are critical on overvoltages, but tend to allow for a wide degree of charge current options at better efficiencies compared to standard flooded lead acid types. this is somewhat irrelevant as your main goal was to offset the generator run times meaning much of the power generated by the pvs can go straight to the loads at a good efficiency if the batteries are fully charged to start. this means that it is not imperative to go with 3 pvs if you choose not to. i do have to point out that if something goes amiss with your general generator charging that you could use the solar setup to do it. the better the charge percentage would then be more important than just supplementing power use.

"QUESTIONS ABOUT HOW TO CYCLE THE BATTERY'S SOC:
IS THERE ANY WAY TO QUANTIFY (OR EVEN JUST JUDGE BY SOME RULE OF THUMB) THE LONGEVITY/EFFICIENCY TRADEOFFS? IS THERE A "SWEET SPOT" ALONG THE ACCEPTANCE CURVE WHERE YOU GET YOUR BEST VALUE OUT OF YOUR SOLAR CAPACITY? WHAT WOULD YOU RECOMMEND FOR A STRATEGY FOR CYCLING THE SOC? HOW DOES THE SULFATION ISSUE APPLY TO GEL AND AGM BATTERIES? DOES ONE NEED TO EQUALIZE? HOW FREQUENTLY SHOULD ONE ACHIEVE A 100% SOC? IS THERE A BIG DIFFERENCE AMONG BRANDS OF BATTERIES IN TERMS OF SETTING A CYCLING STRATEGY? IS THERE AN OVERALL RECOMMENDATION FOR A MANUFACTURER OF AGM BATTERIES?"

loaded with questions here. every situation is unique and can nullify our rules of thumb and it is difficult to nail efficiencies with precision. as far as i know the gels and agms can sulfate even if it takes longer to do so. the best solution is to get to and stay at 100% soc as often and as long as is possible, but if we talk of batteries just sitting with no charge to them then they can survive quite a long time before needing a boost type charge and that's because of the low self discharge rates they see. most will put a float charge on and not need to worry about needing to boost charge after a month or 2, but again, this applies to stored batteries and not batteries actively being used out in the ocean. i also will advise against eqing either of these types you can use as they are voltage sensitive. it is more an option some manufacturers give to recover a bit of lost equality on old or abused batteries. the cycle life of many batteries is one thing you would need to consider and the batteries with a good lifespan tend to cost more. our host carries the sunxtender line of agms, but there are others too that are good. if you weren't going solar i'd have told you to go with the gels you have for replacement, but like i said they are picky on the charge current and not just the voltage. 10yrs is a good lifespan for those gels, and i must add for many other batteries too.

i hope i didn't miss anything here.

vtmaps

Re: Solar Sailboat System; Seeking Advice

Hi s/v apha wave,
I don't know much about boats, except perhaps that the sun reflecting off the water can be intense. Regarding the location of the panels, do you have any locations where you can put vertical panels? You might be surprised at how much power you can produce by reflection. You would probably want several controllers if the panels are facing a variety of directions.
--vtMaps

Windsun

Re: Solar Sailboat System; Seeking Advice

niel wrote: »

any good quality mppt controller is fine and note that any of them could put a spike right where you want to operate. only 2 are certified for low emissions and that's the midnite classic and the xantrex mppt60. the tristar may work fine for you too, but it all depends as one may have a certified cc that may put a spike at say s7 where you want to operate and the non certified cc may not have a spike where you want to operate and may throw a s9+15db signal just outside your place of operations somewhere. do look into the midnite classic controller though as it can handle far more current and is feature packed, but at a slightly higher price. a monitor may help you track battery soc, but it may have a degree of innacuracy too.

The Morningstar TriStar 60 MPPT meets FCC Class B Part 15. The Outback controllers are about the only current ones that do not.

niel

Re: Solar Sailboat System; Seeking Advice

Windsun wrote: »

The Morningstar TriStar 60 MPPT meets FCC Class B Part 15. The Outback controllers are about the only current ones that do not.

good (fixed typo) to know as i may have known it and forgot.

as said there aren't any guarantees that a spike of noise won't be on his operating frequency even with a certified controller. odds are any of those mppt ccs would do fine, but if he should need to improve things further he could go to the sticky in this link to get ideas on how to improve the noise should help some,
http://forum.solar-electric.com/showthread.php?5887-Radio-Noise-from-PV-System

CDN_VT

Re: Solar Sailboat System; Seeking Advice

My Take .
Web feet & a Rope twister myself . 60+ cutter rig Sloop.

Most Important thing is In my eyes is Panel mounting & protection from being stood on to high winds ripping off a poorly mounted install.

Build a few running handles / stops around the sides to grab before landing on the panel.

YOU will always have a shade area on the panel , just pull the boom or anchor off bow with a cross tie break to keep the vessel one sided , (always use a tension break for the cross tie) Just like going astern is great on any Sailboat (this is when the Popeye's shine).

As with the third panel to add later (over the dinghy davits aft of the transom )is NOT any way of making sure that it will help.It will be more bother, Physical & truly electrical,now how are you going to series in and not have a weak junction. Most who are not salty , don't realize that cuts don't heal well wet, and if it falls off your boat , the sea gods own it...

Im Not a huge lover of wind-gens on boats , BUT , as long as it is Up out of the way of any head strikes & removed under sail , approaching storms , then hanking one up the forstay-mast and feeding a separate CC to the windlass feed wires(im assuming you have huge power cables fed forward 4 windlass + ) back to the battery's is another thought.

My Morningstar CC's seem quite , Radios, tunes, 5.1 surround , Now the Yanmar diesel is noise electrically , PLUS !!

VT

Please post what you have built & pictures are always enjoyed ..