Help me wire this, please

[skipmac]

Hi tinkrman69.

Some answers for you and how I would do this.

Originally Posted by tinkrman69

Whats the rated output of the panel? whats the rated Amp/hr of the batteries in each bank. what is the stimated daily amp/hr usage. What latitude are you normally in?

OP stated 2 X 75 amp hour 12V batteries and a 120W panel.


Say I have 60 amp/hr usage, one banks amp/hr rating should be 3x that and my solar out put should be at least 2x the usage. which will screw you on a week of cloudy days you'll need some other source of temporary charging. ok I'm around the 25th parallel so 400 watts of solar will give me an average of about 120 amp/hrs a day. I have 15 ft of actual run to the charge controller. I'll need a pos, neg and ground

I didn't look at the specs for his controller but don't think it would take three wires. Normally 12V DC doesn't use a separate ground to individual devices, just a + and - with the negative being the ground.

of 8 gauge wire or equivalent, to the controller I'll need the same to the batteries two bank controller, two banks. run pos & neg from bank 1 on controller to pos & neg on bank i do same with bank 2.

Unless the OP has some other requirements, if this is just for house bank then it's generally better to combine the two batteries into one house bank.

your not cranking engines so #4 or even #6 wire would work to the batt switch. I'd use #4. run pos of each bank to the perspective terminal on batt switch run same size wire from common on switch to pos busbar. run same size wires from neg terminal on batt bank to neg busbar.

unless you charge controller states otherwise do not run its neg to the common neg. your controller will decide which bank needs the most charge.

All the DC negatives end up together unless the boat is wired quite strangely so no reason to run separate negative wires to the batteries even if they are separate banks.

Run the ground from the panel to the engine block or other path to earth. not through the neg side of your circuitry. any ground circuit should always be as close, in the electrical path, as it can get to earth. not in the beginning,not in the middle, but at the end as close as you can reasonably get to earth. the water your floating is earth.

hope this will help you. there is a book by Don Casey "sailboat Electrics simplified" It will answer all your previous questions plus all the ones you didn't know you needed to ask. and all the terminology is based on a high school level. So, easily understood. Hell I know a housewife that excelled through it and now fixes her own stuff.

Don Casey's book is excellent. If you want to get deeper into the technical details Nigel Calder's book is good.

[GrahamHO]

I would use 2 charge controllers and 2 panels. Then a simple isolating switch between the 2 batteries which should (normally) be in parallel. That is positive to positive and negative to negative with the isolation switch in the connecting positive line.
When isolated each battery is charged by each panel and when combined they will both be charged by both panels.


It's probably OK to run 2 charge controllers off one panel but not what I would do.

[GrahamHO]

I didn't read carefully enough.

You have a duo charge controller so that is like having 2 separate charge controllers from one panel. I wired a small single Mornigstar controller yesterday so the duo is probably similar. ( that one was to keep a car charged while I'm away)


There will be 2 terminals probably on the left showing + and - for the panel. If you are not sure use a cheap digital multimeter and it will show something like 19v with the panel in the sun and if it is -19v it's the other way around.

Then to the next right there should be 2 sets of terminals with a battery symbol on each maybe labeled bat 1 and bat 2. The + and - of each goes to each battery and they will be isolated from one another in the controller. Always put a fuse (spade is best) near the battery + terminal connection of each.


Then next right with Morningstar there is probably a + and - terminal with a light bulb symbol for an auxiliary connection. I usually ignore them but make sure the screws are tight. Then there should be on the far right side 2 terminals with a small plate connecting them. If you have sealed batteries leave the plate in and then the max charge will be limited for sealed batteries that you can't top up. If you have flooded batteries that you can top up with water take that plate out and throw it away.


As you want to be able to isolate each battery from one another put a heavy starter type cable from each battery + to each side of a decent isolation switch. The 2 negatives are joined together at whatever common earth you have, probably your engine transmission connecting bolts. Don't have 2 battery earth connections in 2 different places on your engine as there could be a slight voltage difference between them which could increase electrolysis.


You should of course have another isolation switch on each battery + going to their respective loads i.e. starter or house etc.


The fuse size on the controller battery + connections depends on the panel size but would normally be 5 / 10 amps. If you are not sure try 5 amps and assuming your wiring is OK if it blows go to 10 amps.


The controller should be as close as practical to the batteries. That is to avoid regulated voltage loss in the connecting cables. The length of the panel cables doesn't matter as much as the voltage in them is unregulated.


All your wiring should use tinned marine cable including the battery cables as plain copper rots away in salt (foggy) air.


I have 3 Morningstar controllers but not a dual one. I'm just going by their usual layout of terminal connection.


I see you are in Monterey. We enjoyed a couple of days there last Oct and looked around the yacht marina and at the resident sea lions, and had fish and chips on the pier as you do. I don't envy your fogs and I suppose you can sail out past them.


An Alan Wright design will be a good sound cruising boat. I once had the pleasure of meeting him in his very small design office overlooking the Hauraki Gulf in Auckland NZ about 20 miles from where I live.

[Dexterbase]

I have the Morningstar Duo charge controller shown here.

I am not set on maintaining the two batteries as separate banks and from what I've read here it sounds like its best to combine them into one bank.

The wiring diagram included with the charge controller makes it pretty easy to understand how they want the charge controller wired to the batteries, but wiring the batteries to the three way switch and the dc bus is what I'm not totally clear on.

I included the wiring diagram from the manual and an idea of how to wire up my setup.

Am I sort of on the right track? Your help is very much appreciated.

[Yeti]

I feel like I should clarify this...

In the drawing I posted the "panel" is your DC electrical switch panel and not the solar panel. I didn't reference the solar panel at all as there is only one place the solar panel can go and that is directly to the charge controller as indicated in the manual.

I also assumed you have a 1, 2, or both type of 3-way switch. There should be no negative wires on this switch at all. The negative wire for the solar panel should go to the charge controller. The negative wires for the battery banks should be to the common ground (the negative buss bar in the drawing). The DC electrical switch panel negative wire should go to the common ground as well.

[Yeti]

Here's a new drawing for everyone's excitement!

This one has the batteries tied together in one bank, includes the solar panel, and both the positive and negative buss bars.

I haven't drawn any fuses but you should certainly fuse things as described in the Duo Charge manual. Also others have mentioned fusing the batteries. Its not a bad idea at all. Here's a great article about that: Battery Bank Fusing Photo Gallery by Compass Marine How To at pbase.com

Use buss bars with several points of attachment so that the battery terminals are not stacked with a bunch of wires. As things grow you'll find them useful.

[GrahamHO]

Originally Posted by Dexterbase

I have the Morningstar Duo charge controller shown here.

I am not set on maintaining the two batteries as separate banks and from what I've read here it sounds like its best to combine them into one bank.

The wiring diagram included with the charge controller makes it pretty easy to understand how they want the charge controller wired to the batteries, but wiring the batteries to the three way switch and the dc bus is what I'm not totally clear on.

I included the wiring diagram from the manual and an idea of how to wire up my setup.

Am I sort of on the right track? Your help is very much appreciated.

Regarding the 3 way switch: buy a cheap $10 digital multimeter. Set the knob on the middle of the Ohms scale that is shown by an Omega symbol. Then touch the two meter cables together and the meter should read 0000. That shows they are connecting. Then go around the switch checking which terminals connect together and are showing 0000 with the switch in its different positions. If it shows nothing or just a vertical line they are not connected.

Draw a plan of that.

Apart from doing it for you that's the best I can suggest.

The multimeter has a 9 v battery inside it and passes its current through the test points of the switch showing they are or aren't connected. 0000 means no resistance showing a good connection. The meter will also be handy later setting it on 20v DC to check voltages at different connection points when you are wiring up. You don't need to use all the other meter settings yet.

[ramblinrod]

This is a little more complicated than posts imply.

Do you have electric start on the engine? If so, per ABYC, the engine starting battery should be isolated from the deep cycle house battery (different models) and the start battery must be connected to. The alternator when the engine is running without user intervention.

If you do not have electric start on the engine, both batteries should be deep cycles.

Re: battery isolation. If engine and deep cycle, I would recommend it. Connect alternator and starter to battery 1(start) switch position. Connect house battery to bat 2 switch position, and common tondc panel positive connection. Connect all negatives together.

If 2 deep cycles, isolation is optional. The advantage is that a bad battery can be easily isolated. The disadvantage is that unless left in "both" position all the time, the battery charge/discharge treatment will not be equal and capacity percent minimal, so battery life expectancy will be reduced.

Re fuses: There has been some bad advice posted. The house battery terminal fuse is sized to the current rating of the wires to the DC panel or max rating of the DC panel, which ever is less. Loads don't come into it. Loads are protected by branch circuit fuses or breakers.

Additionally, the solar charge controller fuses ( within 6 " of the battery or via battery terminal fuse) are sized per solar charge controller manufacturers instructions or 10% higher than the charge controller max output.

12Vdc batteries store sufficient energy to burn you and your boat if mishandled or wired improperly. By asking this question it is clear you are not knowledgeable in boat wiring standards and practices. Therefore. I recommend either studying ABYC wiring standards or referring the job to a (certified) marine electrical professional.

(Many here will suggest this is not necessary, prolly the same ones that have given you bad or wrong advice.)

(Others will advise that they had some professional do something wrong. BS, likely some unqualified person. Very unlikely a certified marine electrical technician would mess up a charging system (though everyone and anyone, even the absolute best can make a mistake now and again.) 95% of DIY electrical mods I see are wrong and in many cases patently unsafe endangering life and property needlessly simply due to lack of knowledge or skill.

Ramblin Rod
Certified Raymarine Installer

[skipmac]

Hi Rod,

Some good advise but some points I would recommend a different approach.

Originally Posted by ramblinrod

This is a little more complicated than posts imply.

If the OP has electric start engine then yes there's a lot more to the question.

If you do not have electric start on the engine, both batteries should be deep cycles.



Re: battery isolation. If engine and deep cycle, I would recommend it. Connect alternator and starter to battery 1(start) switch position. Connect house battery to bat 2 switch position, and common tondc panel positive connection. Connect all negatives together.

This is where I would disagree. It is better to connect the alternator output directly to the battery system and not through a switch. Connecting the charge output to the switch allows the possibility of turning off the battery while the engine is running and the alternator charging, which could blow the diodes in the alternator.

If you have a separate starting battery I think the ideal setup is to wire the alternator and all other charging sources to the house batteries (with of course proper fusing) and then connect this to the start battery with one of the automatic combiners like the unit made by Yandina that will send charge to the start battery anytime there is sufficient charge voltage present.


If 2 deep cycles, isolation is optional. The advantage is that a bad battery can be easily isolated. The disadvantage is that unless left in "both" position all the time, the battery charge/discharge treatment will not be equal and capacity percent minimal, so battery life expectancy will be reduced.

Re fuses: There has been some bad advice posted. The house battery terminal fuse is sized to the current rating of the wires to the DC panel or max rating of the DC panel, which ever is less. Loads don't come into it. Loads are protected by branch circuit fuses or breakers.


Excellent advise and very important. A short could start a fire unless the wires are properly fused.

Additionally, the solar charge controller fuses ( within 6 " of the battery or via battery terminal fuse) are sized per solar charge controller manufacturers instructions or 10% higher than the charge controller max output.

Since the output of the solar charging system is limited by its designed capacity, if the proper size wire is used there's no concern about shorting the solar output to start fires but of course you should fuse as recommended to protect the equipment. The real concern is that this is connected to the batteries and a short could dump full battery output to the wire. Same principal applies, fuse at or close to the battery for the size of the wire.

12Vdc batteries store sufficient energy to burn you and your boat if mishandled or wired improperly. By asking this question it is clear you are not knowledgeable in boat wiring standards and practices. Therefore. I recommend either studying ABYC wiring standards or referring the job to a (certified) marine electrical professional.

(Many here will suggest this is not necessary, prolly the same ones that have given you bad or wrong advice.)

(Others will advise that they had some professional do something wrong. BS, likely some unqualified person. Very unlikely a certified marine electrical technician would mess up a charging system (though everyone and anyone, even the absolute best can make a mistake now and again.) 95% of DIY electrical mods I see are wrong and in many cases patently unsafe endangering life and property needlessly simply due to lack of knowledge or skill.

Ramblin Rod
Certified Raymarine Installer

[hellosailor]

If you want to make sure you don't wake up with no battery power one morning...wire them up in parallel but add a "battery brain" to the common positive output. That's a little box which opens a relay and cuts off the battery loads completely when the power drops below an adjustable set point. So, if you run them down to perhaps 12.1 volts? Click, no power. You have to go reset it (manually or with a remote fob) and there's your reserve power, waiting for you.

[Maine Sail]

Originally Posted by Dexterbase

I can't imagine the size of the batteries affecting where to plug what into what though? I may be wrong.

This is a diagram for two 75ah batteries and a kyocera kc-120 panel. Morningstar Sunsaver Duo charge controller.

I basically need to know where to tie the charge coming out of the charge controller to the rest of the system.

This boat sits on a mooring with no access to shore power.

Wire the batteries in parallel and then feed the #1 main output of the Sunsaver Duo to the single bank directly with a fuse in the positive wire within 7" of the banks positive terminal. Set dip switch #3 to OFF. IIRC from a conversation with Morningstar a few years ago, if the SSD senses no load on bank #2 it just acts as a single controller.

Alternatively run them as two banks and feed #1 to bank #1 and #2 to bank #2 and set Dip switch #3 to ON..

Ideally a single controller and parallel batteries will yield the best performance... The SSD is really meant for a house bank and small start bank but it seems you are using your batteries as only house loads and as such a single paralleled bank is the best scenario for many reasons..

[ramblinrod]

Originally Posted by skipmac

Hi Rod,

Some good advise but some points I would recommend a different approach.

Skip Macyou are stating disagreement but also stating exactly what I said. Connect due starter battery positive lead, alternator positive lead, and stater positive lead to battery switch 1 post.

This way, the alternator (and starter) is always connected to she starter batttery so there is no risk of taking out the alternator if the battery switch is switched to the 2 or off position while engine is running (as long as battery 1 is connected of course).

[jwcolby54]

Originally Posted by Dexterbase

You all are amazing.

You are correct, the batteries are 12v 75ah batteries and they're sitting end to end in the battery box. So the consensus is that they're best combined into a single bank rather than treated as separate batteries?

And of course the batteries need to be the same age. Do NOT "add a second battery" in parallel to an old used battery.

[GrahamHO]

Good advice Rambling Rod. I remember seeing a yacht on a swing mooring burning due apparently due to bad electrical wiring. Your best advise is to get a good electrician. I did though have to fix the wiring on a friends boat after a "professional" electrician couldn't.

[ramblinrod]

Originally Posted by GrahamHO

Good advice Rambling Rod. I remember seeing a yacht on a swing mooring burning due apparently due to bad electrical wiring. Your best advise is to get a good electrician. I did though have to fix the wiring on a friends boat after a "professional" electrician couldn't.

Always ask to see their certification card. Anybody can say they are a professional if they do work for hire. They may not know excrement from Shinola. If they are truly qaualified they will have a card in their wallet at all times. If they don't, they're not, don't let them in your boat.