Sanity Check on Wiring Plan

[Target9000]

So. We're about to start rewiring our boat and I wanted some of you guys to look over my shoulder and tell me what I'm doing wrong.

Details 1st:

• Primary bank of 4x6v golf cart batteries.
• Secondary bank of 1 x 12v fla battery primarily for starting.
• 65 amp stock alternator
• 4 solar panels that total up to around 250w
• wind gen probably d400

The main issue I ran into when planning is that our engine came prewired with the starter and alternator connection on a single post on the motor. I'm not sure I really want to tinker with this right now and haven't found any solid diagrams of anyone that has.

I originally wanted to wire the alternator to the primary bank and the starter to the secondary bank as is standard but with only one connection it kind of threw a kink in the works. So instead I thought I'd throw in 2 switches instead of just one.

So the plan would be to leave the ENGINE SWITCH pointed to the Secondary Battery all the time unless it should fail. We would leave the HOUSE SWITCH pointed at the Primary bank unless it should fail. Bilge pumps and other non-switched connections would also go to the Primary bank.

Question 1. What do you think of a double switch system and this wiring plan in general?

Question 2. Our motor has a flexible shaft coupler that isn't metal and the boat has been grounded to a dynaplate. This was done by the PO and I've left it the same for now. Should I change this?



Thanks!

[CharlieJ]

Question 1. What do you think of a double switch system and this wiring plan in general?

It is my opinion that the underlying problem with the traditional 1-2-Both-Off switches is that many, many, many owners lack the operational discipline to properly position the multiple switches correctly. I know its hard to believe, but it is true! Most vessels that I walk on to that are equipped with multiple battery selector switches have defaulted to leaving all of the switches in the Both or All position. I know that is also hard to believe, but it is very true!

So, with this preamble, here is a response that I wrote yesterday to a similar question:

I typically do away with the traditional 1-2-both-off switches and install either simple on-off switches (Blue Sea 6006, 9003e or 3000) or remotely operated battery switches (Blue Sea ML7700) for battery isolation and to simplify the system.

Charging sources are generally connected to the house bank and the starting battery or batteries and the bow thruster and/or anchor windlass batteries are charged with either an ACR (Blue Sea 7610 or ML 7620) or a Balmar DuoCharge.

To continue with simplification of the system, the legacy split house bank system on older vessels is combined to become a single house bank. This philosophy, championed by Nigel Calder, has developed and matured over the last several years and is the generally accepted practice now.

I usually upgrade the connections to the batteries or their bus bars through a compact Blue Sea Marine Rated Battery Fuse (MRBF) that provides circuit protection as close to the source (the battery) as is physically possible. MRBF fuse holders are Blue Sea 5191 (single) or 2151 (double) and fuse are from 30A to 300A, have a 10,000A AIC are ignition protected and have an IP rating (susceptibility to water intrusion) that resists water jets.

The main issue I ran into when planning is that our engine came prewired with the starter and alternator connection on a single post on the motor.

This method is favored by production boat builders because it is easy, and less expensive than providing both a charging path from the alternator and a source path to the starter. Generally the output conductor from the alternator is the bare minimum gauge and will have to be replaced when the alternator is upgraded. There is also the fine point that this arrangement leaves a lot of conductor that is unprotected by an overcurrent protection device (OCPD). To refresh memories, an OCPD is required by ABYC and ISO standards at the conductor's connection to a source. The only exception, for now, is engine starting circuits although some advocate the installation of a high amperage Class T fuse in these circuits.

When faced with your arrangement, I generally split the two circuits. The alternator output is connected to the house bank via an MRBF and the starter is connected to the starting battery via one of the On/Off switches cited above.

Emergency starting current is provided by using another On/Off switch between the house bank and the load side of the starter isolation switch. When emergency starting is required, the starter isolation switch is turned Off, to disable to the starting battery circuit, and the emergency starting switch is turned On bringing starting current to the starter without wasting energy attempting to charge the discharged starting battery.

Now, I will happily admit that my scheme has replaced two, four position switches with three On/Off switches and an ACR or DuoCharge, but the functionality and safety of the overall system has been significantly enhanced.

Question 2. Our motor has a flexible shaft coupler that isn't metal and the boat has been grounded to a dynaplate. This was done by the PO and I've left it the same for now. Should I change this?

This is a difficult question. It is also a can of worms on a forum!

There may be legitimate reasons for "grounding" the boat to a dyna-plate, but very, very few and it is usually done for the wrong reason. I would suggest, in an attempt to keep this thread < 150 responses on the pros and cons of "grounding" the boat to the dynaplate, that you contact the previous owner and ask him why he did this.

In the meantime, technically, unless the dyna-plate was installed for some compelling, technically sound reason backed by science and engineering, you can bond the output shaft of the engine to the drive shaft with a jumper around the flex coupling. The engine, and thus the vessel ground, may or may not be electrically bonded to the drive shaft by this method because of inherent electrical resistance in the transmission.

Let the games begin!

Charlie

[Target9000]

Thanks for the reply Charlie.

I'll take your advice and skip the ground question for now. I adjusted my wiring plan to try to conceptualize what you were saying about the 3 on/off switches. Can you see if this updated diagram is accurate to what you're trying to tell me?




Also, I agree that I'd like to as you said and change the starter and alternator connections to separate banks but I'm not sure how. Our alternator has some sort of strange plug into the back of it instead of typical connection posts. Its put me off trying to fiddle with it along with the rest of the prewiring.

[mitiempo]

Target

I agree with Charlie.

On the alternator the output is either labeled B+ or just +. It is the largest connection and probably the largest gauge wire on the alt. It currently goes to the starter and this is the wire you have to remove. It is replaced with a larger gauge wire direct to the house bank, fused near the batteries. Your diagram shows it going to the emergency start switch - I would wire it directly to the house bank.

[Target9000]

mitiempo,

On my alt there is a weird clip connector for the alt output with apparently two wires that are B+? Take a look at this.

[donradcliffe]

The second diagram gets rid of an unswitched connection from the house battery to the distribution panel which should not be there, but you still need to run an unswitched (but load protected) line from the alternator to the house battery instead of the alternator post.

Do you know which alternator/engine you have? In addition to the plug on the back of the alternator, there should be a heavy (Minimum #4) red wire which runs from an insulated terminal stud on the alternator to the starter solenoid. That's the one which should be disconnected from the starter and run to the battery. If its all wrapped up in an engine wiring harness with some smaller wires don't worry, you should be able to find the other end connected to the solenoid on the same terminal as the really thick cable from the battery switch.

BTW, there should also be a heavy ground (black) wire which runs from an stud which is not insulated from the alternator case to the common ground point, but its probably missing in your boat.

[mitiempo]

I see. I would remove both from the alt, leaving a short length. I would install ring connectors on each and using a small powerpost or similar join them and the new wire that goes direct to the house bank.

[Target9000]

Originally Posted by donradcliffe

The second diagram gets rid of an unswitched connection from the house battery to the distribution panel which should not be there, but you still need to run an unswitched (but load protected) line from the alternator to the house battery instead of the alternator post.

Do you know which alternator/engine you have? In addition to the plug on the back of the alternator, there should be a heavy (Minimum #4) red wire which runs from an insulated terminal stud on the alternator to the starter solenoid. That's the one which should be disconnected from the starter and run to the battery. If its all wrapped up in an engine wiring harness with some smaller wires don't worry, you should be able to find the other end connected to the solenoid on the same terminal as the really thick cable from the battery switch.

BTW, there should also be a heavy ground (black) wire which runs from an stud which is not insulated from the alternator case to the common ground point, but its probably missing in your boat.

Thanks Don, I accidently left that unswitched connection to the panel in the first diagram and tried to remove it before I posted but for some reason photobucket is being cranky.

Please see the wiring diagram for the engine above. It shows all the connections. I'm just worried about cutting wires that run into the alternator clip.

[donradcliffe]

Now I see your engine wiring diagram, the path of least resistance would be to lift both the B+ wires off the +Ve terminal and splice them to a cable to the house battery. While you're at it run a #4 wire from the B- terminal to the -Ve terminal to prevent future problems.

[mitiempo]

Originally Posted by Target9000

Please see the wiring diagram for the engine above. It shows all the connections. I'm just worried about cutting wires that run into the alternator clip.

They are both alternator output wires as shown by the schematic - they just doubled smaller wires. I would cut them as I described above.

[Target9000]

Originally Posted by donradcliffe

Now I see your engine wiring diagram, the path of least resistance would be to lift both the B+ wires off the +Ve terminal and splice them to a cable to the house battery. While you're at it run a #4 wire from the B- terminal to the -Ve terminal to prevent future problems.

What would be the proper color of this wire and what is its purpose? To ground the alternator I'm assuming? Why would this have not been done from the factory?

[mitiempo]

I think it is case grounded where it attaches to the engine.

[donradcliffe]

Originally Posted by Target9000

What would be the proper color of this wire and what is its purpose? To ground the alternator I'm assuming? Why would this have not been done from the factory?

I would be black wire and it would be to ground the alternator. The alternator is grounded to the engine -Ve through its mounting system, but when things get old and rusty its nice to have a direct wire, especially for high output alternators.

[Target9000]

You guys are great. So if I spliced the 2 x B+ wires to a feed to the house bank and grounded the B-....

Would you go with a 1/2 switch again like this?

[donradcliffe]

Your last diagram will work, but not as well as the previous switch setup. It saves switches, but where are you going to leave the switch?? Are you going to remember to switch to the start battery every time you start the engine, and back to the house battery when the engine goes off. Probably not, and like 95% of the people you are going to end up leaving it on 'ALL", which defeats the purpose of the start battery and the ACR.

The other reason for not doing it this way is that the starting load will pull the voltage down on the DC panel far enough to make some of your electronics unhappy--in my case the radar and the AIS transponder need to be reset after every engine start. Its much better to isolate the house loads from the starter circuit.

The 3 off-on switches wiring is more of a PITA to start with, but you can set it and forget it.