Solar system - 'real world' help needed!

[BobLoucks]

Yes, 300w won't help
Sorry typo I meant 2-3000w inverter

I figure that i need about 1500 watts to deal with microwave, induction burner and the coffee maker. Not all at the same time of course
Thanks

[roland stockham]

Thanks for a really useful and detailed reply. I have added a few comments others may find interesting

Originally Posted by ramblinrod

Responses in red.

Hi All, I am not currently cruising full time but make extended trips (2-3 Months) and may not have shore-power when docked
Just looking at ordering the parts for a solar charging setup and need some advice from people who have used this stuff, it's my first system! have read all the bumph and many threads on here but if you have experience with solar could you look over the system and comment. Thanks


Congrats!

Boat. 35ft classic, Radar, small fridge and autopilot are main consumers and all lights etc are LED. Nav is by tablet and only on for coastal. From experience I use 50-75a/h per day. This may go up a bit as I have just installed a more powerful pilot but I also have a wind vane. I occasionally get up to 125 when running nav, auto pilot and radar 24-7 plus making lots of coffee!!! (the electric kettle gets used when it's iffy and I can't stay below to work the stove).


50 A-hr today when running electric (assumed) refrigeration is pretty light. Most fridges will draw 50 A-hr per day on their own. For your size of boat and amenities, I recommend planning on 100 A-hr per day. - Roland, consumption fig are from real life taken from several year coastal and ocean cruising. Fidge is a small mobile unit and only uses 25ah/hr day even in the carribean but yes I want to be able to use 100ah/day without worry

At the moment I find that, on a long run, I don't have the engine on for long enough to fully charge the batteries so they go down to about 85% and stay there, bad for the batteries and reduces power available if it is needed.

This is concerning. If your batteries start out in the morning at 50%, and you motor till evening, with your set-up the batteries should be at 100% or darn close. Check to ensure that your regulator is sensing the battery voltage and not the diode isolator voltage. - Roland, Yes that would fully charge everything and then some. Typically when coastal I will motor for 20min to and hour to clear the anchorage then be under sail. On passage I run the engine for about 2hr every 2and or 3 day which gets the batteries up to about 85-90% but would need a very long run to fully charge. On the trip north I will be at sea for about 6-8 weeks and fuel supply becomes a concern as there are areas where calms are common and I need to keep the fuel for that not batt charging

That said, 85% SOC with an alternator is about what most shoot for (shutting down the engine when this is reached) as the acceptance rate of the batteries (standard FLA (Flooded Lead Acid) diminishes as the SOC (state of charge) increases. To charge higher requires an inordinate amount of running time. - Roland, hence the solar installation 4-6 charge at 5-10a

Electrics. Externally regulated 90a alternator, 2 batt banks one about 350a/h for domestics, one 300a/h for nav and ships gear. 3 way diode to batteries. Charge acceptance with low batteries is greater than the alternator will produce (about 70a at 2000rev). I am happy to continue to use the alternator for bulk charging if needed.

My recommendation is to get rid of the diode isolator, and combine all deep cycle batteries into one bank. (- Roland, would still need a distributer of some sort for the start batt, not keen on relays as they are expensive and seem less reliable but may be worth considering.) This helps assure that the overall battery SOC is higher and the batteries last longer, as compared to drawing down a small bank while the other bank is fully charged. When you replace the batteries, go for same make and model for all (unless you have an isolated start battery, which may be different.) - Roland, I really lke to keep a separate system for the 'ship supply' it reduces radio interference by isolating all the 'dirty machinery' from the electronics and prevents drop out of things like the GPS if a domestic load drops the voltage below 10.5v which can happen with things like the kettle or vacume cleaner. I also like to have the reserve of knowing I can run nav and running lights for a couple of weeks if the charging system goes down regrdless of where the house bank was. The nav batteries are additional, 400a/hr is a good size for the house bank on my system.

Your alternator is pretty much right-sized in my opinion (for standard FLA batteries). If your batteries are at 50% SOC or greater, they will take the full alternator output for some time, and then as they charge the acceptance rate will limit what they can take from the alternator. A larger alternator will only save you a few minutes of charge time to 80% state of charge, in practice.

What I want the solar system to do is;
1. Keep/recharge batteries when the boat is unattended.


If a 600 A-hr battery bank is at 50% SOC (300 A-hrs), meaning full consumption for 3 days with no solar charging whatsoever (unusual) a 400 W system would bring it up to full charge in 2-3 average sunlight days.

2. Reduce engine run time so that normally I will not need to run the engine either underway or at anchor.

For 100 A-hrs / day consumption, I recommend a 400W system. On an average day, this will replenish everything consumed. If you live aboard full time, I would bump this up to 600W (if you have the mounting real estate) to allow dipping into your battery capacity on cloudy days. - Roland, only way I can get to this is with twin 250w panels, sounding like this is the way to go if I can fit it

3. If I have used more power and need to run the engine I want to do the bulk charge in the morning from the alternator but for the solar system to then get the batteries back up to full charge during the day.


Yup, that's typically what folks want a solar charger to do. - with 250w sounds like I will need to run the engine every day or so but the batteries will then get to full charge by afternoon so that will be good even though it still uses some diesel.

The system I am looking at is a 245w Kyocera panel and SOLARBOOST3000i 30A 12V MPPT PV CHARGE CONTROLLER.

Questions
1 Can I hook the panel to the diode block on the alternator input, does the controller have remote batt sense or can it be adjusted to compensate to the diode voltage drop (about 0.75v)?


RTFM (Read the friggin manual). (Roland - right! but you cant always get the manual until you buy the kit!) First, I assume you mean can the "CHARGE CONTROLLER" be connected to the isolator. The answer is yes, but don't. Again connect your house banks together, and connect the charge controller to the single house bank (via proper fuse.) Roland - Will look at connecting via a small VCR to each battery, may be worth it to avoid the power loss even if it is only 10w or so, will find out what their power transfer efficiency is.

Most MPPT controllers will allow adjustment of the charge voltage to compensate for a diode regulator, so this is an option if the controller doesn't have (or come with) a battery voltage sensor. Just because you can, doesn't mean you should. Isolating house banks from each other does more harm than good.

2 If I get a second panel will I also need a bigger controller? What happens if the panels occasionally produce more than 30a, does it simple limit the current or will it blow the controller?

First of all, don't go with a single panel mounted athwartship. If any part of it is shaded, the output will be killed. - (I can see the issue here and potentially the radar dome could cast shade, mounting 2 panels one in front and one behind it would mean one was always clear, splitting to 4 small panels would not help much as one pair would still be shaded. Sailing into the sun is also an issue as the whole stern is shaded by the square sail until the sun is over the yard, panel layout will make no difference!) The more discrete panels mounted athwartship, the less impact of shading one. For a 400W system, this would be 4 x 100W panels, each being about 2'W x 4'L. If your bimini is large enough to support this, you're golden. Roland - I could do this by mounting a pair of 100w panels next to each other but it reduces total output by 45w and more than doubles the cost (100w panels are $2+ per/w 200+ panels are under $1) so for the same about budget I would get a total of 200w using 100w panels or 500w with 245w panels

3 In the real world sailing from Panama north to Canada what am I likely to get in A/h day from this panel?

With a 245 panel mounted athwartship (partially shaded most of the day), about 30-40 A-hrs. With a 4 x 100W panels mounted parallel to centreline, (average one panel shaded at a time), 110 A-hrs / day. Roland - So 250w is going to be fine as long as I can insure no shading, 500w would be OK even with shading as it would give me 60 - 80 a/hr

Do you think it will be big enough? I am guessing I will get about 60% rated output for 6h/day with a peak of about 90% allowing for sun angle and transmission losses, is this about right?

I make calculations based on 4 hours of 100% rated output / day avg. It works out close to what you have with your calc. IMHO, 245W in a single panel is a bad idea. 2 x 125W panels will do you much better. Still this will only generate about 80 A-hrs / day, which I suspect is under your average daily consumption, and does not allow for less than avg. sun.

4 I have seen various controllers on Ebay as direct purchases from China which would save $100-200. I have had good results buying LED lights that way but anyone used controllers from there and were there as expected?

I sell low end and high end controllers. If you are living aboard and really counting on the system, I recommend higher end. As with every country of origin, some products may be good and some not so much. You need to determine whether the price is lower because of the lower labour rate, or quality corners cut. This is compounded by the E-bay channel. A bricks and motar retailer who has been in business for 20 years, is not as likely to flog crap as a new E-bay start-up out of garage. Roland - done some more research on this by loong at some reviews on U Tube, confirmed the worry that many of these are junk so will only go that way if I can get a trusted independent review.

PS, I only sell locally, mostly what I install, so I have nothing to gain here.

5 Do people rig panels so they can be taken down for storm conditions or will they stand up to 50kn if well mounted?

Nope. The installation should withstand 50 knots, no problem. Handling the system for every afternoon thunderstorm is likely to cause more damage than it saves. Roland - great, although I was thinking more about hove to for a couple of days in 50kn+ than a squall, Mexican coast and Gulf of Alaska can both be nasty at times

I may be able to fit a second panel if needed but getting concerned about windage and loading on the stern arch if I do. It would also be over the stern above the rudder and windvane so a bit vulnerable. Some extra windage will be good as she has a high bow that tends to blow off.

Again, I would recommend at least 2 panels, more is better. Windage really comes into play when healed. Leave a gap between panels, bigger gap is better. A flat rack is better than an arced one for windage and presentation to the sun.

The footprint of an 8' x 4' panel array (like the 400W system recommended) is smaller than the bimini on most modern 35' sailboats. Roland - good point, I used to have a small mizzen that set about 45sqft of sail and that balance the boat nicely. As you say lots of boats have permanently rigged biminis. Mounting locaion is aft of all rigging over the aft deck (and will create anice shaded seating area so will add a comfy seat to the stern rail. This is also where the emergency tiller is so double+)

If panels are mounted a couple inches above a bimini, they don't present any signifcant windage more than the bimini itself. Mounting above the bimini, may often result in shading by the boom. Shifting the panels aft of the bimini (at least partially) may reduce shading but increase windage. Exposure to physical damage isn't really a problem, as if you run into something that close astern or abeam, you have other issues.

Regardless of mounting, the 4 x 100W System recommended, would not produce much more windage than the single 245W panel you are considering. Roland - That I don't get surely windage depends on panel area and 400w is almost twice 245 so will have almost twice the windage?

Happy Sailing,
Ramblin Rod
Marine Service Provider
About Sheen Marine[/QUOTE]

Again thanks for the reply, definitely helped with the design even if I don't agree on all you points!

[Nicholson58]

Originally Posted by roland stockham

The system I am looking at is a 245w Kyocera panel and SOLARBOOST3000i 30A 12V MPPT PV CHARGE CONTROLLER. Is the panel open circuit voltage high enough to enable boost? We run a similar load as you describe but we were able to mount 3X220 watt Sanyo HIT panels = 660 watts of 54 VDC open circuit for our 24 VDC system. (parallel panels, 3 diodes per panel) You probably have researched the panel efficiency available. We picked ours 4 years ago at about 18.5%. I think higher efficiency is available now.
Questions
1 Can I hook the panel to the diode block on the alternator input, does the controller have remote batt sense or can it be adjusted to compensate to the diode voltage drop (about 0.75v)? My gut feel is that the diode bridge drop is a bad idea. I think you should go directly to the battery. All installers and suppliers of solar charge systems will tell you to oversize the wires and avoid voltage drops as much as possible. There are charge controllers capable of charging two banks. Otherwise, you could put in a battery selector to choose the bank to be charged. You will also need to run a sense wire from each bank to a selector switch back to the charge controller so that it senses the bank being charged.
2 If I get a second panel will I also need a bigger controller? What happens if the panels occasionally produce more than 30a, does it simple limit the current or will it blow the controller? The controller should be chosen large enough to handle the maximum total watts you might plan to have available and at the highest open circuit voltage. In most cases on a boat, you experience partial shading. This is a killer to panel output. To mitigate, make sure the panels have divider diodes, usually three or more per panel to drop out shaded sections. Add panels in parallel, not series, for the same reasons.
3 In the real world sailing from Panama north to Canada what am I likely to get in A/h day from this panel? Do you think it will be big enough? I am guessing I will get about 60% rated output for 6h/day with a peak of about 90% allowing for sun angle and transmission losses, is this about right? Most estimate around 50%. Your numbers are in the ballpark. As you head north, the incidence angle will be less optimum so expect lower performance as you make way north. 90% is only likely where you get the sun close to normal to your panels. Not really likely.
4 I have seen various controllers on Ebay as direct purchases from China which would save $100-200. I have had good results buying LED lights that way but anyone used controllers from there and were there as expected? After my own research, I bought well known name brand MPPT from Morningstar. Nice features & easy to use with the optional digital panel added. Others have used a variety of controllers.

On the Chinese lights, be sure you get what you really wanted. Many LED makers use a choke resistor to control the current. This wastes a lot of power as heat. Like the MPPT charge controller, the better lights have a time-proportioning current regulator on board the element. It will cycle at around 30 KH to minimize EMI radio interference. They are often rated 9 to 30 volts and are polarity blind. I suggest you read the technical from Marine Beam - good information. https://store.marinebeam.com/why-marinebeam-1/ The technical guide is hear with good links worth reading. https://store.marinebeam.com/technical-info-1/

5 Do people rig panels so they can be taken down for storm conditions or will they stand up to 50kn if well mounted? Yes, some do. I would remove them if you are gone for an extended time or for a hurricane. On our install, I wired each our three panels through its own two-pole 10 amp circuit breaker. Panel wiring is combined after the breakers and then into the charge controller. Output of the charge controller goes through a 40 amp two bole breaker. The sense wiring from each battery comes to a double pole, double throw switch with center OFF and then to the charge controller. This way, any panel and the charge controller can be isolated in a storm or for maintenance. After the 40 amp breaker, the MPPT output goes through a large rotary battery selector; BAT 1 - OFF - BAT 2. All wiring is big and short to minimize voltage drop. Panels are #8. After the breakers, #6 to the combiner. After that, #4. If you are running from the stern arch to mid-ship you may want to jump your panel wiring to a heavier gauge.

I may be able to fit a second panel if needed but getting concerned about windage and loading on the stern arch if I do. It would also be over the stern above the rudder and windvane so a bit vulnerable. Some extra windage will be good as she has a high bow that tends to blow off

Hope this helps.

[ramblinrod]

Roland - On passage I run the engine for about 2hr every 2and or 3 day which gets the batteries up to about 85-90% but would need a very long run to fully charge. On the trip north I will be at sea for about 6-8 weeks and fuel supply becomes a concern as there are areas where calms are common and I need to keep the fuel for that not batt charging.

Yes, this is very normal. For this reason, it is wise to size the battery bank planning on using only 30% of it's capacity (50%-80%). So if you budget to consume 100 A-hrs / day, and from 80% state of charge, you don't want to dip below 50%, after 2 days without sun, you will need 200 A-hrs / .3 = 650+ A-hrs.

(- Roland, would still need a distributer of some sort for the start batt, not keen on relays as they are expensive and seem less reliable but may be worth considering.)

My preference is all deep cycles in one bank. If you have a big enough house bank, high loads will not dip the voltage. Many people start off a large house bank. If you wish an isolated cranking battery (my preference, but which I don't currently have) my recommendations are ACR (best) , A/B/Both/Off (second best) Diode Isolator (third best). In relation to the whole scheme, the cost of an ACR is negligible.

Roland, I really lke to keep a separate system for the 'ship supply' it reduces radio interference by isolating all the 'dirty machinery' from the electronics and prevents drop out of things like the GPS if a domestic load drops the voltage below 10.5v which can happen with things like the kettle or vacume cleaner.

To each there own, but if your house bank is 600 A-hrs (combined) and your wiring is correct, you should not have any issues with a high inverter load taken the bank down below the low voltage drop-out of the GPS. If this is happening, check your DC grounding, cabling voltage drops, and connections to the battery.

I also like to have the reserve of knowing I can run nav and running lights for a couple of weeks if the charging system goes down regrdless of where the house bank was. The nav batteries are additional, 400a/hr is a good size for the house bank on my system.

Again, you can do whatever you want, but if you have 600 A-hrs of batteries aboard, regardless how you split them up, you still only have 600 A-hrs of batteries aboard. Breaking the bank does not give you more reserve capacity. All breaking the bank will do, is drop that bank to a lower state of charge if you forget (and you will) to manually balance the load.

- with 250w sounds like I will need to run the engine every day or so but the batteries will then get to full charge by afternoon so that will be good even though it still uses some diesel..

It sounds like you are overly concerned about getting your batteries up to 100% every day. Don't. Those last few percent are very hard to come by. If on a bright sunny day, you get to 95%, that's great, but if your charge cycle is consistently between 50-80%, with an occasional full charge, that is ideal.

Roland - I could do this by mounting a pair of 100w panels next to each other but it reduces total output by 45w and more than doubles the cost (100w panels are $2+ per/w 200+ panels are under $1) so for the same about budget I would get a total of 200w using 100w panels or 500w with 245w panels .

I am not sure if you are getting the point here. If you are, great, maybe this will help others.

Lets assume a nice sunny day, where we can get 100% of a panels rated output. However, panel that is partially shaded, even one half of one cell, kills the output of the panel.

If a single cell of a 245W panel is shaded, output is zilch (0W).

Now split that panel into 2 x 125W, and if one cell is shaded, one panel is dead, but the other having no shade is giving max output (125W).


Choosing a single panel to get the most rated Watts / $ may be false savings due to shading.

When I inspect a boat for potential mounting locations, shading is the primary issue to overcome. Avoiding shade is virtually impossible, anywhere on a boat. The goal is to minimize the impact of shading.

For a 400W system, I generally recommend 4 x 100W panels.

Yes the $ / rated W is a bit higher, but then again, the actual real output will also be higher.

Roland (re windage) - great, although I was thinking more about hove to for a couple of days in 50kn+ than a squall, Mexican coast and Gulf of Alaska can both be nasty at times

OK, this is different than an afternoon squall. When a storm of 50+ knots is coming, it is prudent to duck for cover or reduce windage as much as possible.

So if you expect conditions where a bimini would likely need to be taken down, then it would also be prudent to take down an equal sized area of solar panel(s).

Dare I say that it would be much easier to take down and find stowage for smaller panels in the preceeding 20 knots than one big panel? ;-)

Roland - That I don't get surely windage depends on panel area and 400w is almost twice 245 so will have almost twice the windage?

Yeah, not the strongest point here, but comparing apples to apples, 2 x 125 square inch panels, can present less windage than a single 1 x 250 square inch panel.

RamblinRod
Marine Service Provider
About Sheen Marine

[bobw100ton]

I concur totally with Ramblinrod's response, but I believe something important has been overlooked. The industry has conditioned everyone to buy dollars per watt, when in fact you should be looking at dollars per daily watt hours produced per square ft/pound. Whenever we upgrade one of our Kyocera arrays with SunPower the equivalent daily production can be made with 40% less surface area. More importantly, a 3" hard shadow
across the Kyocera will cut-off most of the production while the SunPower only looses 5%. SunPower panels cost more than double Kyocera if you just want to feel better about watts/dollar but not if you consider the real objective. Steve Dashew of Deerfoot Yachts and FPB Boats orders SunPower as a standard array on his boats for this reason. It's all about cell efficiency, Kyocera 14.5%, SunPower 22%.