Thoughts on my Solar Plan

[JK_Boston_Catalina310]

Hello Maine Sail and others,

Happy New Year! 2015 is setup to be exciting for us as we plan to head out cruising in about 10 months.

Part of our cruising prep is adding solar to our boat. Here is my plan. I would appreciate any thoughts or comments you may have.

Here is a quick summary of what I have been planning:

1) Living on the hook I am estimating we will use between 50-125 amp hours per day;

2) We are willing to run our diesel engine up to 1.5 hours a day allowing are alternator to generate about 65 amp hours, plus producing hot water as a by-product;

3) That would mean that we would want to generate about 50 amp hours of solar power a day;

4) Given that we are going in a small boat, efficiency is important, so we would like get the increased 15-20% efficiency you get from an MPPT controller over a PWM controller;

5) We may decide to add a watermaker to our boat and would like the ability to expand our solar array to offset some of that power consumption. So that would mean we would want to size certain aspects to allow for the easy upgrade in the future;

6) We like the aspect of the semi-flexible panels since they would allow us to disassemble and store the panels more easily in the event of a storm, and;

7) We are NOT independently wealthy and are trying to do this cruise in a very cost effective manner, so we can’t afford to splurge on the best available product for every component.

All that being said, here is what I have come up with for the our solar array:

- Two (2) 100 watt semi-flexible solar panels mounted on our bimini;
- A 30 amp MPPT controller with a remote panel, and;
- An ability to expand the system by added two (2) 100 watt semi-flexible solar panels on the life lines or on deck.

I am planning to go with the Renogy semi-flexible panels. I can fit two of the 100-watt panels without having them cross any bows for the bimini. I plan to mount the panels with velcro like Maine Sail has shown before. I know I need to stiffen the bimini frame to do this and will get that completed before I put the panels up there.

I know one downside to the cheaper panels seems to be consistency. From reading reviews and recommendations, mainly from Maine Sail, on the sailing forums it appears that the best practice is to do some side by side testing as soon as you get them in. To do this I will make a 2×4 A frame that I can temporarily mount the panels on. I will then hook up the each panel separately to the charge controller and a battery. I will let each panel run for an hour and record the performance to make sure they are in the same ball park. I plan to record the starting, mid charge and ending volts and amps at the battery and the charge controller. If the results from each panel are not within the expected range I will send them back until I get a set I am comfortable with. This is another good reason to go with the Renogy because they are Amazon Prime eligible and that will help if I need to send them back.

As I stated above, I want to go with an oversized MPPT charge controller. I looked at the Rogue MPT-3048, MidNite KID, TriStar 30, TriStar 40 and Blue Sky SB3024iL. This list primarily came from an article on the Compass Marine site about adding a small panel plus some recommendations I got from cruisers. I briefly considered some lesser brands such as the Renogy but decided that this piece was important enough to not mess around with off-brands.

Some of my key concerns were that I wanted flexibility to change the charge profile, the ability to equalize, a temp sensor and a remote panel. I plan to mount the controller in the stern compartment near the shore power charger and holding tank. I am concerned about the heat aspect. I don’t want to mount this unit in the cabin and have it dissipate heat into the cabin while we are in the tropics. I would also like some secondary ability to know what is going into the batteries besides the our Victron Battery Monitor.

In the end I found that the Rogue MPT-3048 had the best balance of options for the cost. It comes standard with a temp sensor and voltage sensors. The cost for adding the remote panel wasn’t bad. It didn’t hurt that it was among the cheapest. Still talking over $400 when all is said and done.

I plan to wire the two panels on the bimini in parallel. From what I have read, you want to wire solar panels on a boat in parallel as that handles partial shading on a portion of one panel the best. If they are in series shading would degrees the output of the panels more. I am going to use the MC4 connectors for the panel wiring. This seems to give a good connection that can be disconnected easily when needed, yet another good Compass Marine article on this subject. I also plan to use the Renogy MC4 branch connectors to make the parallel connection at the bimini. I like how you can choose which side to make the male and which to make the female so you can make it dummy proof so you can’t connect them in reverse polarity. The Renogy panels come pre-wired this way.

Here is my proposed wiring diagram. Getting a little busy and I might need to find a way to clean it up a little. I am attaching a PDF as well in case anyone wants to add comments on my wiring.

Please let me know what you think.

Thanks,

Jesse

 

[Maine Sail]

Sounds good but I would suggest experimenting with parallel & series before locking in a decision.. I would also come into the boat with 10GA (short runs) and bump it from there to the controller.

 

[Bill Roosa]

If you want to clean up the diagram thing circles. all electricity is in circles. start at the sources of electricity at the top ,on the left hand side are the CB/switches at the bottom are the loads and then return to the source via the right hand side.

 

[IStream]

Just one point about panel testing. I've found that if you put all the panels under test in similar lighting conditions and measure the open circuit voltage and the closed circuit current of each panel, you can get a very good sense of how well matched they are. I've done this under very different lighting conditions, at different times, and with different loads and find that the results are the same as a single Voc and Icc measurement at one illumination level, which takes less than a minute per panel.

 

[Brian M H23]

Just some late night musings here....
I would suggest you start using the correct units for your calculations, given the investment you're talking about here. Power per day" is watt*hours, an alternator running at a fixed "amp" output will put out it's amps * battery bank voltage * engine run time = watt hours. Especially as if the device list grows to include devices that run at various voltages, AC or DC, etc, you can generally keep counting watt hours.

The rouge can also take advantage of a 100V solar array and the installation manual suggests wiring the panels in series. It also calls for fusing between the PV array and the device. (The fuse should be sized to the wire, but I think you know that)

As for the remote voltage sensing wires - Seems like massive overkill, even if you had fifty feet of #10 wire you have .05 ohm, likely insignificant compared to connections. Given that you have 12' of #4 wire for 20-25 amps, you have no reason to add extra connections

Lastly, you've got five things running to a 3-fuse bus bar with splices right next to it. Seems much cleaner to fuse each device individually and do away with the extra splices.

 

[1bajaboy]

JK, Your drawings are great... One old salts advice "use less amps"...=less head ache?? If you use mats all over your decks you can run a reefer and charge you batts. For the Flatscreen and watermaker a small genset works. I hate running the IronJib to charge batts...........yea ,Mark Twain was cool!

Brad
Hiouchi, Ca.

 

[Rummerful]

Very good write up. I will be studying it. One thing that concerned me was running the engine for 1.5 hrs everyday. We cruised for almost 7 yrs and tried very hard not to need to start the engine every day. We did put on a high output alt so when we did run the engine, it quickly topped off the batteries.
Eric

 

[JK_Boston_Catalina310]

Just some late night musings here....
I would suggest you start using the correct units for your calculations, given the investment you're talking about here. Power per day" is watt*hours, an alternator running at a fixed "amp" output will put out it's amps * battery bank voltage * engine run time = watt hours. Especially as if the device list grows to include devices that run at various voltages, AC or DC, etc, you can generally keep counting watt hours.

Thanks for the advice.

The rouge can also take advantage of a 100V solar array and the installation manual suggests wiring the panels in series.

Maine Sail made a similar suggestion. So my plan to wire the panels in a way that I can try both parallel and series connections and see what produces better.

It also calls for fusing between the PV array and the device. (The fuse should be sized to the wire, but I think you know that)

I did see that in the manual but I have never seen Maine Sail advocate putting fuses or breakers in this location. Something I will have to research more.

As for the remote voltage sensing wires - Seems like massive overkill, even if you had fifty feet of #10 wire you have .05 ohm, likely insignificant compared to connections. Given that you have 12' of #4 wire for 20-25 amps, you have no reason to add extra connections

The #4 wire was to bring the power to the batteries, not for the voltage sensing. The voltage sensing wires appear to be 14 gauge.

Lastly, you've got five things running to a 3-fuse bus bar with splices right next to it. Seems much cleaner to fuse each device individually and do away with the extra splices.

Those aren't splices. I will just add the terminal lug to the terminal post on the ANL fuse holder.

Thanks for the comments.

JK

 

[JK_Boston_Catalina310]

Very good write up. I will be studying it. One thing that concerned me was running the engine for 1.5 hrs everyday. We cruised for almost 7 yrs and tried very hard not to need to start the engine every day. We did put on a high output alt so when we did run the engine, it quickly topped off the batteries.
Eric

I can see that approach. If we were going to be in far out areas I would consider this a problem. But since we are only planning on the Bahamas and the Caribbean I don't expect this will be an issue.

Having previously discussed the whole running the engine to charge batteries issue with Maine Sail and others, I am comfortable that this approach will work for us. And we have already been doing it similar to this when cruising locally.

Thanks,

Jesse

 

[Maine Sail]

Just some late night musings here....
I would suggest you start using the correct units for your calculations, given the investment you're talking about here. Power per day" is watt*hours, an alternator running at a fixed "amp" output will put out it's amps * battery bank voltage * engine run time = watt hours. Especially as if the device list grows to include devices that run at various voltages, AC or DC, etc, you can generally keep counting watt hours.

The rouge can also take advantage of a 100V solar array and the installation manual suggests wiring the panels in series. It also calls for fusing between the PV array and the device. (The fuse should be sized to the wire, but I think you know that)

As for the remote voltage sensing wires - Seems like massive overkill, even if you had fifty feet of #10 wire you have .05 ohm, likely insignificant compared to connections. Given that you have 12' of #4 wire for 20-25 amps, you have no reason to add extra connections

Lastly, you've got five things running to a 3-fuse bus bar with splices right next to it. Seems much cleaner to fuse each device individually and do away with the extra splices.

The problem with using watt hours for batteries are that most deep cycle batteries are rated in Ampere Hours for capacity. To compound that boaters, including JK, very often use Coulomb counters or Ah counters on boats. These devices count Ampere Hours and correct for Peukert very few count watt hours.. Watt hours are a correct unit of measurement for energy but with batteries and Ah counters we rely on ampere hours as our measurement of energy used....

As for the voltage sense wires they are a good tool, if you have them, and they allow for the controller to compensate for any voltage drop in wiring, across fuses or terminations. I routinely measure .5V to 1.5V+ drop in charging systems and this is a performance killer.

I agree that with 4GA there should not be much, if any, but even if it is just .2V that can make a difference in the speed the batteries can recharge at, when in absorption mode. For the slight cost of some 14GA wire I'd certainly make use of it...

The requirements for land based systems are different than on boats hence Rogue's fusing suggestions to cover land based requirements.. Under marine standards, ABYC, the panels are considered current limited sources and thus for boats we only place fuses within 7" of the + battery terminal... We also rarely use series panels on boats due to shading so we are dealing with low voltage and low current.

Series can work on boats but it needs to be tested on the specific boat both ways, over time, to see which way performs best on the given boat while swinging at anchor. I only have a few boats where series out performs parallel and these are boats where panel shading is very limited.

 

[walt]

Just one nit pick - and maybe not even a real issue but it might be of interest... (I like the use of different colors in that diagram!)..

It looks like you have four 100 watt panels wired in parallel and want to use an MPPT controller to get the most out of what the panels produce. I will make an assumption that the panels and the controller have a 30 foot run of wire between them (60 foot round trip) and this is the 10 gauge wire shown on the diagram.

With MPPT and especially panels in parallel, you have to be concerned about power loss in the wire. Some number for your case..

10 gauge wire is 1 ohm/1000 ft. So 60 foot of 10 gauge wire is .06 ohms.

The 400 watts of panel might create 22 amps of current.

Power loss in the wire is I*I*R (i.e., I square times R).

Power loss in the 10 gauge wire run between the panel and the controller = 22*22*.06 ohm = 29.14 watts.

You started off with 400 watts at the panel but lost 29.14 in the wire. I.e., you lost over 7% of the power in the wire run between the panel and the controller.

This will reduce the 15 to 20 percent MPPT gain over a PPM controller you want to achieve by 7%.. I.e., the best you will get is 8 to 13%.

This is just an example.. since we don’t know your exact wire run lengths but you may need considerably larger than 10 gauge wire if there is a long run between the controller and the panels. It’s the trade off between serial or parallel panels. You have to use more copper with parallel panels.

edit.. looking really close at your diagram.. it looks like you may only have 1 foot of that 10 gauge wire in the diagram between the panels and the controller and 12 foot of four gauge between the controller and the batteries (everything must be at the aft end of the boat). Assuming the 12 guage runs between the individual panels and the panel bus is also short, maybe you dont have any issue -- in which case everything I said above doesnt mean anything . But.. if you want to get the 15 to 20 percent gain of MPPT, you need to worry about the wire loss.

 

[JK_Boston_Catalina310]

Just one nit pick - and maybe not even a real issue but it might be of interest... (I like the use of different colors in that diagram!)..

It looks like you have four 100 watt panels wired in parallel and want to use an MPPT controller to get the most out of what the panels produce. I will make an assumption that the panels and the controller have a 30 foot run of wire between them (60 foot round trip) and this is the 10 gauge wire shown on the diagram.

With MPPT and especially panels in parallel, you have to be concerned about power loss in the wire. Some number for your case..

10 gauge wire is 1 ohm/1000 ft. So 60 foot of 10 gauge wire is .06 ohms.

The 400 watts of panel might create 22 amps of current.

Power loss in the wire is I*I*R (i.e., I square times R).

Power loss in the 10 gauge wire run between the panel and the controller = 22*22*.06 ohm = 29.14 watts.

You started off with 400 watts at the panel but lost 29.14 in the wire. I.e., you lost over 7% of the power in the wire run between the panel and the controller.

This will reduce the 15 to 20 percent MPPT gain over a PPM controller you want to achieve by 7%.. I.e., the best you will get is 8 to 13%.

This is just an example.. since we don’t know your exact wire run lengths but you may need considerably larger than 10 gauge wire if there is a long run between the controller and the panels. It’s the trade off between serial or parallel panels. You have to use more copper with parallel panels.

Thanks but you estimated way too much distance.

The two panels on the bimini will have a wire run of less than 20 feet, closer to 15 feet. The port side panel will have less than 5 feet and the starboard side will have around 15 feet.

Jesse

 

[walt]

Yes, I saw that after looking at your diagram closer..