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Battery Charging System - Am I Correct?

Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
I'm installing a refrigerator into my Hunter 28.5. As with projects of this nature, I opened a can of worms. Adding the refrigerator draw into my energy consumption calculations - guess what - I need new, larger A/Hr batteries. Yeehaa!

I'm not putting $580.00 dollars worth of batteries into the boat and then charge them off of a NAPA plug-in car charger. Maine Sail has a thread regarding battery selector switches. I found it once looking for something else, but it stuck with me. Attached are two pictures, the first is a photograph I found in the thread, and the second it a block diagram I drew to understand better what Maine Sail had written and showed in the photograph.

I would like to make sure I my understanding is correct. Some question though:

- The Blue Seas fuse holders I found come with 6 ga leads. The longest positive run is 6 ft at the most. Is 6 ga large enough? What amperage fuses should I be using?
- In the photograph is shown a "From Batt Switch Feed". Is this from the common terminal on the selector switch?
- Is the shunt necessary, if so, what is recommended?
- Ship ground. I'm not sure where this would go other than the common ground at the engine block.
- I'm planning on using knife style SPST battery disconnects, is this a good choice?

I thank you in advance for all advice and corrections,
Alec
 

Attachments

Oct 19, 2017
5,295
O'Day 19 Littleton, NH
- The Blue Seas fuse holders I found come with 6 ga leads. The longest positive run is 6 ft at the most. Is 6 ga large enough?
I don't know much about this subject, but I'd like to follow this thread.
I do know 6 ga is huge. It's what I buried under ground to run the 200' to the fence for my chickens, turkeys and bees. I'm running about 1000' of 12 ga electric fence on it. There is almost no measurable drop in the 3.2 joules output across it.

-Will (Dragonfly)
 
Jan 11, 2014
4,420
Sabre 362 113 Fair Haven, NY
- The Blue Seas fuse holders I found come with 6 ga leads. The longest positive run is 6 ft at the most. Is 6 ga large enough? What amperage fuses should I be using?
Which fuse holders are these? For fusing off of the battery, the easiest least expensive system is a MRBF, Terminal Fuse Blocks - Blue Sea Systems

The longest positive run is 6 ft at the most. Is 6 ga large enough? What amperage fuses should I be using?
First measure the run as a round trip, i.e., both the positive and negative leads. Thus going from the battery to the refrigerator and back will be 12 feet.

Fuse to protect the wire, there are ampacity tables available that will tell you the maximum rating. The wire size is determined by the load, the distance and allowable voltage drop.

- Is the shunt necessary, if so, what is recommended?
A shunt is not necessary for the circuit. However, if you have an ammeter, the shunt is necessary to measure the current draw. It goes between all the loads and the battery negative post.

- Ship ground. I'm not sure where this would go other than the common ground at the engine block.
The ship's ground is the ground on the engine block. There should only be one connection there.

- I'm planning on using knife style SPST battery disconnects, is this a good choice?
I think that would be a poor choice. Use battery switches designed for the purpose.

Based on your questions, I think you have a lot to learn yet before embarking on a major rewiring project. One of the best sources of information for the beginner is Charlie Wing's book, Boatowners Illustrated Electrical Handbook. Read and study that book and spend time on MaineSail's website: www.MarineHowTo.com
 
Oct 22, 2014
10,671
CAL 35 Cruiser Portland OR, moored EVERETT WA
Alec. I think @dlochner has given you some good points. I glanced at your diagram and am not sure that the Battery Select switch is actually doing anything. as there appears to be multiple connections to your Positive terminal block. When you begin this idea best to double check your paths.
 
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
Just wanted to check back in and let you know I'm working on things after reading @dlochner reply. I'm going back over my work and manufacturer's wiring diagrams, as well as Maine Sail's how to site. Some things have become clearer to me. Some things I'm still working to understand. Some times my poor little brain just gets tired and I need to go play solitaire.
 
Nov 24, 2015
48
Hunter 27 Middle River
I did a comprehensive rewire of my H27, and found the Blue Seas website/catalog invaluable. They have a wire size calculator that incorporates wire type, routing (through engine compartment?), peak and average loads, etc., and even tells you what fusing type and size to use. That and the chapter on boat electrical systems in Don Casey's book taught me so much that I didn't know and needed to. My vessel is now ABYC compliant, and has been trouble free for years, electrically speaking.
Mind you, I have decades of experience in electronics and aircraft wiring but I didn't know how much I didn't know about marine wiring and systems until I started reading the sources above.
Tip of the hat to Blue Seas and Ancor wiring. Expensive, but so is a tow home. Or a fire.
 
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
Revised design.

A couple of things to mention. After reviewing wire gauge charts, 6 awg is fine. All round trip runs are well below the 30 ft shown in the charts. The ProMariner ProTournament battery charger was the wrong one for this application. I went back to ProMariner's website and found the ProNautic 1230 battery charger is better suited.

I began the the re-design with how the boat is currently set up. I used the ProNautic information and the Blue Sea information for their model 8084 panel to add those into the system. Moved the alternator connection to the house bank as an input also moving the house bank to terminal 1 of the battery selector switch. The connection to the auto bilge pump is moved to a direct output at the house bank.

I'm comfortable and confident in this design.

The ProNautic charger will charge house and reserve independently, though both banks must be of the same chemistry. The panel's DC ammeter is accounted for, as well as the DC voltmeter. The panel has its own selector switch to monitor voltage independently from the battery selector switch. I have traced all positive ins and outs and and am satisfied that positive flow are correct. Negative flows all terminate at the engine block with one exception. The ProNautic is grounded to the engine and the ship's ground at the keel with the lighting grounds for the mast and stays.

I've attached my design and the wiring diagrams for both the ProNautic charger and the Blue Sea panel
 

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Maine Sail

Moderator
Feb 6, 1998
11,052
Canadian Sailcraft 36T Casco Bay, ME
Revised design.

A couple of things to mention. After reviewing wire gauge charts, 6 awg is fine. All round trip runs are well below the 30 ft shown in the charts. The ProMariner ProTournament battery charger was the wrong one for this application. I went back to ProMariner's website and found the ProNautic 1230 battery charger is better suited.

I began the the re-design with how the boat is currently set up. I used the ProNautic information and the Blue Sea information for their model 8084 panel to add those into the system. Moved the alternator connection to the house bank as an input also moving the house bank to terminal 1 of the battery selector switch. The connection to the auto bilge pump is moved to a direct output at the house bank.

I'm comfortable and confident in this design.

The ProNautic charger will charge house and reserve independently, though both banks must be of the same chemistry. The panel's DC ammeter is accounted for, as well as the DC voltmeter. The panel has its own selector switch to monitor voltage independently from the battery selector switch. I have traced all positive ins and outs and and am satisfied that positive flow are correct. Negative flows all terminate at the engine block with one exception. The ProNautic is grounded to the engine and the ship's ground at the keel with the lighting grounds for the mast and stays.

I've attached my design and the wiring diagrams for both the ProNautic charger and the Blue Sea panel
Charger chassis ground should only go to the engine ground or ships main DC negative bus not two places.

Installing a Marine Battery Charger (LINK)


.
 
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
Charger chassis ground should only go to the engine ground or ships main DC negative bus not two places.
So in this case I should ignore Pro Mariner's wiring diagram and ground either to the ship's ground at the keel or the the engine block - correct? I'm still a bit confused by what you term the ship's ground as the main DC negative is grounded at the engine block. Should the main DC negative ground go to the ship's ground at the keel?
 
Last edited:
Jan 11, 2014
4,420
Sabre 362 113 Fair Haven, NY
So in this case I should ignore Pro Mariner's wiring diagram and ground either to the ship's ground at the keel or the the engine block - correct? I'm still a bit confused by what you term the ship's ground as the main DC negative is grounded at the engine block. Should the main DC negative ground go to the ship's ground at the keel?
The ProNautic diagram shows the case ground going to 2 places, it should only go to one place. The case ground is different from the DC Negative ground. The case ground is to the metal frame of the charger and grounds the metal case in the event that either AC or DC should short to the case.

Route the case ground to either the DC Negative busbar or to the ground on the engine block, not both.
 
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
I still don't understand why ProMariner wants grounding to both. I have sent them an email asking for clarification. This is what the instruction manual has to say:

"3. Ground - This is extremely important and often overlooked. There is one common battery
ground with the positive battery connections on the ProNauticP. There is also a “Chassis Ground”.
a. Battery Negative - As shown in the diagram, this is connected to a bus bar or terminal
stud (not included) that can handle, at a minimum the amperage of the charger output
(1260 = 60 amp minimum). This conductor shall be of equal size to the DC positive conductor
chosen above. The battery negative terminals are connected to this bus bar or terminal stud.
b. Bonding Stud A.K.A Chassis Ground - This stud is connected to the boats bonding system
as well as the bus bar or terminal stud mentioned above. This conductor is permitted to be
one size smaller than the DC positive conductor chosen above; in the case of a DC to the
case fault, this conductor is critical in carrying the fault current to trip the fuse or breaker,
the AC ground CAN NOT handle high DC amperages."

Charger chassis ground should only go to the engine ground or ships main DC negative bus not two places.
The ProNautic diagram shows the case ground going to 2 places, it should only go to one place. The case ground is different from the DC Negative ground. The case ground is to the metal frame of the charger and grounds the metal case in the event that either AC or DC should short to the case.

Route the case ground to either the DC Negative busbar or to the ground on the engine block, not both.
Unless ProMariner can give me a better reason to ground to both, I'll follow the advice from Maine Sail and dlochner. I'm also attaching a new drawing removing the second ground of the charger chassis - thinking about someone in the future who may stumble upon this thread.
 

Attachments

Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
Have just received a response back from ProMariner - that was quick! This is the explanation I was given. Not sure it changes anything though.

"The ground stud connected to the boat ground point on the engine is to carry any DC current should there be an internal DC short to the metal case plate.
The connection to the bonding system is simply to be sure the case is at the same voltage as the rest of the bonding system to prevent galvanic corrosion of the case plate."

This still doesn't explain why the DC negative ground is interconnected to the chassis ground. Or, in terms of galvanic corrosion, the ship's bonding system (I'm still under the impression that this is the lighting bonding at the keel) why both grounds are necessary, both ground to the same patch of water.
 

Maine Sail

Moderator
Feb 6, 1998
11,052
Canadian Sailcraft 36T Casco Bay, ME
Quote:
b. Bonding Stud A.K.A Chassis Ground - This stud is connected to the boats bonding system
as well as the bus bar or
terminal stud mentioned above.
This conductor is permitted to be
one size smaller than the DC positive conductor chosen above; in the case of a DC to the
case fault, this conductor is critical in carrying the fault current to trip the fuse or breaker,
the AC ground CAN NOT handle high DC amperages.
"

Fixed their manual for you...:biggrin:
 
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Likes: DaveJ
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
:laugh: Thanks Main Sail!

Anything else you would change, or can I fly with this setup?
 
Nov 16, 2012
856
Catalina 310, 2000, #31 Santa Cruz
You might want to consider an ACR of some sorts so that your reserve battery will be charged by your alternator without you having to turn the battery selector switch. That would also eliminate the wire from the charger to the reserve battery.

I also think you need more fusing at your batteries. The Blue Sea MRBFs are a great way to do that; either on the battery stud, or at a bus bar.
 
Last edited:
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
You might want to consider an ACR of some sorts so that your reserve battery will be charged by your alternator without you having to turn the battery selector switch. That would also eliminate the wire from the charger to the reserve battery. Just a thought.
I did have that thought originally. Take a look at the drawing from my first post.

Now, however, with the the ProNautic charger, I'm working with this thought: The reserve battery is keep at full charge in maintenance mode with shore power. If I need the battery to start the engine, after starting the engine, switch back to bank 1. If I must go to bank 2 because of failure of bank 1, then it's time to cut back on all but essential equipment (if this means shutting down the refrigerator, so be it) to get me to a port where I can get the services needed to put bank 2 back on line.

If I were in a situation of making multi-day passages, with a port far away, I would reconsider the situation. I'm a Great Lakes sailor. Even taking a full cruise of the all the lakes, I'd be bouncing the shores.

The integration of an supplemental energy source - solar and/or wind - is where things will get interesting.
 
Jan 11, 2014
4,420
Sabre 362 113 Fair Haven, NY
If you start with a good foundation for your electrical system, i.e., a good charger, good wire runs, and a neat installation, modifications down the road can be completed easily. For example you may find it better to run the 2 house batteries as on bank and have a separate third battery. A few cables and an ACR and you are there. Adding solar? With a positive bus bar with extra space, easy.
 
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
If you start with a good foundation for your electrical system, i.e., a good charger, good wire runs, and a neat installation, modifications down the road can be completed easily. For example you may find it better to run the 2 house batteries as on bank and have a separate third battery. A few cables and an ACR and you are there. Adding solar? With a positive bus bar with extra space, easy.
So, as I asked Maine Sail, do you see this as a good foundation, or any other reason not to wire the system as shown in my last diagram?