Adding Solar Panels - Looking for best practices

[RSB333]

We are adding flexible panels to our Bimini this year, and we're looking for the latest techniques and advice. Will also replace our FLA batteries with two T31 AGM's and plan to install a Sterling "Alternator - to - Battery" charger to boost the output from our 55 amp original equipment alternator. We haven't been able to run our Adler Barber refrig. in the past as the drain on the batteries was unsustainable. But with the new system we plan a 100 AH daily electrical usage. Your advice and comments welcome!

[Pete7]

Quite a few members on CF are reporting rather short life from semi flexible panels and I have given up fitting them. In the UK the price of large 250w> panels has dropped significantly. Its cheaper to buy a rigid 300w panel than a 100w, so I did. Could this be an option for you as I don't know anyone who has ever said they have too much solar power.

You haven't mentioned an engine start battery, do you have one or is it just the two Group 31s.

The Sterling alternator to battery widget isn't cheap at £382 on their website, compared to their external alternator regulator at £140. Sure you have to take the regulator apart and solder on a couple of wires to find the field wire, but its not the end of the world and a substantial saving.

The alternator is a bit small, have you thought about one slightly bigger? I am not talking about hundreds of dollars for a Balmar but there must be something like this states side. I have just received mine and will fit it as soon as this lock down is lifted, as it's an upgrade from 60A to 100A

https://www.startermotor-alternator-...73-15372-p.asp

I have a Sterling external alternator controller to fit because the latest have both battery and alternator temperature controllers and a 3 stage charging profile. The alternator temperature will be important if you try to charge a house bank from what is a standard car alternator. They will run for years just topping up a car battery, but up the output and use it in a hot confined boat engine compartment then its going to get hot and suffer reduced life.

Final thought, do you have a battery monitor gauge to see what's going on with charging and depth of discharging? strongly recommended to help manage the power requirements.

Pete

[Ded reckoner]

We have rigid panels, but an acquaintance indicated they were well into their third year using flexible panels mounted on their bimini. The panels were held down using Velcro. The panels had never been removed for any reason including high winds.

[Lucid]

I used flexible solar panels. I recently purchased a new boat and put two on the Bimini. My last boat the panels were held on by 3M Velcro. And it worked well. The panels get better and smaller every year so if you sew Velcro to the Bimini and you have to change them for some reason the foot print will be different. What I did was attache the panels to a piece of matching canvas and then zippered the canvas to the Bimini. That way if I need to change anything I don’t have to perform surgery on the Bimini. If you go the Velcro route make sure the wind can not catch an edge and work it’s way under the panel. I put little leather pockets at the comers on my first install. Another observation, keep it simple. You will get lots of advice on the number controllers you need etc. go with the minimum and make sure the wires and fuses are correctly sized. I have close to 300 watts with two flexible panels and it handles the electrical load for 42 ft sail boat just fine.

[ussvdharma]

Suggest you stay away from 100-200 watt panels. When a panel fails, like a batter it is probably one cell. So Use as many smaller panels as practical. When one goes, wire around it. just my opinion. de W7KFI

[iliohale]

Install a charge controller for each panel - makes a big difference in the overall output of your system if any panels are subject to shading.

[PNWSalmon]

Don't forget about connectors, and figuring out where to run and install them. I was frustrated with my first installation that the dealer didn't even suggest adding on some connectors, I didn't even think about it (speaking of best practices), and then I had to go back and figure it out. My Solara panels have three wires and need to connect to a diode box that isn't waterproof, so I wanted a way to quick disconnect to store the panels away if needed and make the connection to the diode box possible.



We ended up with some fairly substantial, three pin connectors that have a high water resistance rating, this winter they're leaking like mad and already corroding, so it's back to the drawing board to figure out why they've completely failed to keep water out (I'm hoping it's my error, but they don't come with any installation instructions either).



I'm new to solar (obviously), but I found the installation to be very involved. From figuring out where to mount, how to mount, to installing the controllers, programming the controllers, wiring everything. I could have really used some best practices and help, but given how each boat is pretty much unique, I guess I can understand why there isn't a lot of easy guidance or help to be found. I'll be watching this thread and hoping to learn more.

[guyrj33]

Originally Posted by RSB333

We are adding flexible panels to our Bimini this year, and we're looking for the latest techniques and advice. Will also replace our FLA batteries with two T31 AGM's and plan to install a Sterling "Alternator - to - Battery" charger to boost the output from our 55 amp original equipment alternator. We haven't been able to run our Adler Barber refrig. in the past as the drain on the batteries was unsustainable. But with the new system we plan a 100 AH daily electrical usage. Your advice and comments welcome!

looks like you're planning on two group 31 AGM batteries with a total capacity of about 200AH. You expect your daily energy usage to be 100AH.
That implies you will be relying on charging during the day and starting at 100% capacity to prevent your bank being discharged below 50% capacity.
I think your proposed bank is too small for your planned usage.
Also think you would be better off to stick with FLA batteries, as I understand AGM charging needs they need to get to 100% more often than FLAs.
Yes, as others have suggested a bigger alternator would be useful.
If you have the space I'd fit 4 FLA Golf Cart batteries giving you a total capacity of 450AHs, then a 100AH usage would represent a 23% capacity usage.
I haven't looked up the Sterling device you mention, but if you have a 55amp alternator that's the most you'll ever get out of it. In reality it will rarely output 55 amps and if you try to trick it into full output it will overheat.

[Jack C]

A lot depends on where you are going to sail, expected life and other factors. When panels get hot their voltage drops. They are black and absorb heat. Air flow under the panels adds cooling. Laying flexible panels on a cloth bimini limits the cooling. So where you sail in terms of heat buildup matters.
Flexible panels have reduced life if the are continually flexing. Their advantage is that the can take the contour of the deck or bimini and dont need a support structure. But without being well supported they will flex and have a short life.
Flexible panels are a lot more expensive whereas rigid panels are now very cheap and can last 20 years. But they need a support structure. They are also more efficient than flexible panels.
On my 3 boats I have built a light weight but strong structures which can be disassembled if the boat needs to be shipped. I use the rigid panels as a bimini or the rear part of the bimini and add as many panels as I can to take up the available space. If there is a danger of shading I connect in parallel otherwise serial which allows be to use a smaller gauge wire. On my O'Day 39 I have 410 watts along with two wet cell Trojan 6V 380AH batteries and a MPPT controller. We spent summers off grid running a deep freeze, refrig, and LED lights. We added a panel isolator switch so that the alternator would charge the batteries when motoring. The rigid panels on a 1" tube support structure has survived storms and Hurricanes.
So flexible panels for a quick short term expensive solution without the hassle of a support system is a solution. Just make sure that they are 20+ volts. I believe panels drop a volt for every 12 deg F above 72 deg F. So hot 18V panels can drop below 14volt which means batteries will not charge.

The answer in this case is: "It depends on ......"
Unfortunately like most things in life, throwing money at a problem does not guarantee a solution, it often adds to the problem.

[bcboomer]

A better alternator is available from these guys at a reasonable price.

http://www.all-tek.ca/marine-brushless.html

I've been using their 200 amp model for 2 years with a Wakespeed regulator with good results. The alternator was only $320 CAD.

[stormalong]

I agree with the earlier post that a 55 amp internally regulated alternator in not very good on a cruising sailboat. It will not produce 55 amps for very long and won't properly charge your two group 31s. Also will not properly charge AGMs that can easily be damaged by overcharging. You probably don't want to read this but the charging system for a cruising boat is entirely different from a marina queen.

The best solution is a larger alternator designed for continuous output and an external regulator that can be set for you battery type.

On your solar installation shading is your enemy. Even slight shading of a solar panel will dramatically effect output. Shade from your boom would make the solar useless. The Bimini is a good location if your boom does not extend that far aft. If the boom is over the bimini leave a wide gap for where it sits. I also agree that flexible panels historically have had a short lifespan. I can't comment on newer ones.

I have four rigid solar panels totaling 390 watts above my bimini on mounting brackets I designed. I also reinforced my bimini with two additional supports. My boom does not extend that far aft.

Your boat is 10 ft shorter than mine and you may not be comfortable with the weight of rigid panels. IMO they are worth it. Two of my panels are over 15 years old and still going strong. The other two are about 5 years old. I an using a PWM controller that is adequate. When I first went solar MPPT controllers did not exist. Now MPPT is the way to go. Solar has become so inexpensive that I would suggest that you go with as much as you can fit. MPPT controllers will cost more that the solar panels so more panels and a PWM controller may be more economical - do your homework on this.

Don't scrimp on wire size or quality. There is no point in using your solar to heat wire.

[donradcliffe]

Read this thread before you decide on materials and a design.
https://www.cruisersforum.com/forums...-221328-4.html

[MJH]

Originally Posted by RSB333

We are adding flexible panels to our Bimini this year, and we're looking for the latest techniques and advice. Will also replace our FLA batteries with two T31 AGM's and plan to install a Sterling "Alternator - to - Battery" charger to boost the output from our 55 amp original equipment alternator. We haven't been able to run our Adler Barber refrig. in the past as the drain on the batteries was unsustainable. But with the new system we plan a 100 AH daily electrical usage. Your advice and comments welcome!

I am an advocate for solar but not optimistic about your project. Going AGM over FLA is a plus overall but exchanging amp for amp doesn't really make a difference.

I'm not a fan of flexible panels from everything I read in preparation for my project installing 4x140W=560W panels...they are usually smaller and don't have longevity. I think you need to go through the calculations or get a professional opinion of how to power your refrigeration (a big user)...it all comes down to what is required and what your system can produce; you didn't include many details. I also agree with others that a 55A alternator is not very much to backup your solar for the refrigeration. An overall evaluation of your electrical usage and generation will be helpful.

I learned that solar panels are great and not that expensive per se but all the supplemental support stuff that is needed beyond the panels and were to put them is the big driver in overall project cost.

~ ~ _/) ~ ~ MJH

[dlane1181]

This thread has a terrific string of actionable posts. I'll try not to repeat what's already been well stated.

- We just replaced 4x 118watt top-of-the-line Solbian flexible panels with 2x 275watt rigid Victron panels. The Solbian panels worked as well as advertised; however, we experienced delamination of 2 panels ~12 months after the initial installation. Solbian provided outstanding support and replaced all 4 completely free of charge, including shipping from the U.S. to Spain. (Kind of inefficient since they were made in Italy.) The replacement panels look as new today as when they were installed ~15 months ago and have zero signs of delamination. The only reason we replaced the panels early is we changed to a hardtop bimini specifically to increase and maximize solar output in the available rooftop real estate. We will sell 2 flexible panels and use the 2 others at the stern railing.

- Of note, we discovered two small cigarette-like burn marks on the Sunbrella fabric under 2 different panels when we removed them. They had been attached with Velcro on 4 sides directly onto the canvas bimini top. Scary. If I were to redo flexible panels on a canvas bimini, I would put a non-flammable spacer panel between the solar panels and the fabric (several ideas about how to do this) or mount a frame onto the bimini tubing to attach the panels so they "levitated" over the canvas allowing airflow underneath. You could opt at this point, I suppose, to just use rigid panels instead. The added cost of the additional framework would be offset by using the less expensive panels.

- When we used the 4x Solbian flexible panels, each had their own MPPT controller. Now with the larger rigid panels they're in parallel, and we're regulating their charge output with one MPPT controller, at least for now.

[RSB333]

Wow, Many thanks for all the great suggestions. I will re-think the alternator plan.
I had planned on two Victron 75/15 solar controllers, but some of the comments indicated that the output from the panels might be diminished below the voltage needed to charge the batteries. Would running the panels in series -increasing the voltage - through a single larger controller be advisable?


Thanks again!
RSB333