Electrical question for Stu!

[Bob S]

Stu,
First off, I want to thank you for sharing your knowledge and experience in electrical systems. I've been reading this forum for a few years now and have seen the same questions asked so many times. It can gets a little redundant. You have a lot of patience!
I've absorbed all the information you and many others have provided and decided to mirror J Moe's electrical upgrade on the C34 website. Studying his schematic, I had a question. Why would you add a new starting battery switch? Could the emergency battery positive be wired directly to the #2 post then back to the starter? Is this too long a run? I always thought we are trying to eliminate the SWITCH. It looks to me that if that switch was off the echo charger wouldn't be doing it's job.

Bob

 

[Stu Jackson]

Electrical Wiring Diagrams & System Operation

Bob,

Thanks, much appreciated. Your comments have "uncovered" another operational issue with Jim's wiring diagram that I hadn't considered before, and I will eventually use this link to post on the C34 wiki regarding his design.

My favorite phrase is "It all depends on how it's wired." This applies here, too. I have provided extensive discussions of what I call "In Defense of the Simple 1-2-B Switch," both here and on our C34 Message Board.

I disagree, personally, with the two (or multiple) switch arrangements for two reasons:

1. You can use the existing 1-2-B switch to provide what I believe is one of the most important functions necessary: to run your house loads from the reserve bank when necessary without paralleling dead and live banks - like when your house bank has died. MS has posted, and I have agreed, that the house bank is just fine for starting your engine.

2. The multiple switch nonsense only sells more switches! It does NOT improve on what the simple 1-2-B switch can do. You still have to have a paralleling switch, so either it's three switches (like WM suggested a few years ago), or two switches where one is a simple 1-2-B switch ANYWAY!!!, or the super dumb Dual Circuit Switch which only parallels a good bank with a dead one - isn't that really lame!

You could try my contributions from these links from earlier on this board, among many I found from doing a search on 1-2-B switches, exact phrase, author: http://forums.catalina.sailboatowners.com/showthread.php?p=465841 & http://forums.catalina.sailboatowners.com/showthread.php?p=520854 &
http://forums.catalina.sailboatowners.com/showthread.php?t=105813&page=3

The length of the run has nothing to do with it, that's only wire sizing. When you decide what you want to do, simply size the wiring properly on 3% voltage drop. It's always either #4 or #2 because they don't make a #3!

I wouldn't mess with Jim's wiring, it works just fine as shown. "I always thought we are trying to eliminate the SWITCH." Yes, but that's NOT what Jim's diagram / design does, he deliberately adds the switch. Some people simply like to always run their boats by having the reserve bank start the engine all the time - that's what Jim's design does, and see his "Battery Switch Operation" at the top of the diagram. Also see my note about MS's "how-to-start-your-engine" discussion above. We deliberately choose to use the house bank to start, with the reserve in, well, reserve, and always charged. I get on my boat and turn the 1-2-B switch to #1, the house bank, and just leave it there! How simple can ya get?

I also have the option of using the #2 reserve bank to start and the alternator output always still goes first to the house bank. Never through the switch.

I've often linked this following post of mine from the C34 board here on this board, which includes MY wiring diagram which ONLY uses the 1-2-B switch, with the alternator output going to the house bank with a combiner to serve the reserve bank. See reply #8 and the second page for my diagram, reply #23: http://c34.org/bbs/index.php/topic,4623.0.html

My design and Jim's are VERY different.

"Could the emergency battery positive be wired directly to the #2 post then back to the starter?"

NO!!! If you did only that you'd simply have a live circuit all the time and wouldn't be able to switch. Think about it and where the power would go if you did only that.

Here's what you CAN DO - based on Jim's diagram ONLY

1. Take the reserve on/off switch and throw it out
2. Conceptually: Run the reserve (+) DIRECTLY to the #2 post of the 1-2-B switch for power TO the switch and run a wire from the output "C" post of the switch to the starter

To do this you need to do two things:
1) Take what's shown as the "Existing #4 red" between the starter & the #2 post and MOVE it FROM the "2" post TO the "C" post of the 1-2-B switch, and leave it on the starter. This gives you power TO the starter from either bank. It also lets you parallel the banks if your echo charger fails (backup, backup, backup...)
2) Run a new wire from the (+) output of the reserve bank to the #2 post of the switch, without that pesky on/off switch. Do not run ANYTHING from the reserve bank to the starter, go only directly to the switch. (The wiring sizes are your choice.)

You're done.

Bob, what this does is make the 1-2-B switch THE controller for the output to the starter from either of the 2 battery banks (and, of course, to the DP).

It also does exactly what I've been suggesting all along - uses the simple 1-2-B switch to control everything. It changes Jim's design to mine!!!:dance:

1. The 1-2-B switch is only used for battery bank selection and output to two things; the DP and the starter (the "always on" loads can be left as shown or run directly to the house bank or other switches and fuses - your choice)

2. The alternator output goes to the house bank [nowhere near the switch!!!] with a combiner, echo charger, etc. used to supply the reserve bank.

Simple, eh?

"It looks to me that if that switch was off the echo charger wouldn't be doing it's job."

As Jim's wiring diagram is set up, you are completely correct. I spoke with Jim since he published this in 2004, and he noted that based on my suggestion he has moved the echo charger from as shown to the battery (+) posts as recommended by the echo charger manufacturer.

The following is very IMPORTANT to understand: Since his operating concept is to turn the reserve bank switch ON when he gets on the boat and he doesn't leave it plugged in when he's away, what you point out, quite correctly, is not an issue for him if wired this way. Again, you're right: if the reserve bank switch was OFF, and wired this way, the echo charger would NOT charge the reserve bank. Period. If wired to the banks, it wouldn't matter and would always work.

As previously noted, I urge everyone to understand what they're doing and "How It Works." It truly does mean: "It all depends on how it's wired."

There's always more than one way to do things electrically, and thanks again, Bob, for a very good question, and for exhibiting a great understanding of wiring designs and electrical system operations.

Best regards,

Stu

PS You can bet I'm saving this thread!

 

[Bob S]

Thanks again, I'm sure after I digest this I will have another question.

 

[TimCup]

Stu- your answer was perfect-

each question was answered directly, along with the reason, and the reason why not. There are alot of ways to wire a boat, I just don't know why it's not done in the simplest manner for the most advantage.

People keep trying to reinvent the wheel, but always wind coming back to "round".

I appreciate not only your expertise, but the concise writing style you present your ideas with. Thank you.

cup

ps- you can bet I'll be saving this post, too...

 

[Bob S]

Stu

1 Any formulas to calculate cable size? my runs are equal to or shorter than your 34. I would like to use the OEM's as much as possible. I read a recent post on grounding an autopilot and am under the impression there should only be one ground wire to the engine. I beleive this goes back to a bus bar at the DP. Can this be brought back to another bus bar located anywhere else? Your schematic shows a new engine ground bus bar. where did you locate that? I hate to assume but I think your NDP and PDP mean positive and negative battery posts? Can you use a bus bar for the positive side of the battery post?

2 Jim's schematic has the echo charger wired through the switch. I think it should be wired directly between the house and reserve bank, not through the switch. This is how I will do it if you think it's ok.

I'm still trying to figure out what I'll need for wire and fuses before I start.

Bob

 

[Stu Jackson]

Electrical question part 2 back

1 Any formulas to calculate cable size? my runs are equal to or shorter than your 34. ...

2. ...am under the impression there should only be one ground wire to the engine. Can this be brought back to another bus bar located anywhere else? Your schematic shows a new engine ground bus bar. where did you locate that? I hate to assume but I think your NDP and PDP mean positive and negative battery posts? Can you use a bus bar for the positive side of the battery post?

3. ... echo charger wired through the switch. I think it should be wired directly between the house and reserve bank, not through the switch. This is how I will do it if you think it's ok.

Bob,

1. Hike over to your West marine catalog and read the wire sizing guidelines in their electrical section. It's an easy-to-use chart.

2. Bus bar, NDP and PDP: My bus bar is inside the engine compartment. It's a Blue Seas like in the photo below. Yes, you're right about the definition and my NDP and PDP are Blue Seas Power Post Plus, simple posts for connecting wiring. They're in the WM catalog, too. Speaking of which, I have one at home and one on board. Everyone should, or at least some kinda catalog. It's a good idea to have only one engine ground, but as you'll note on my wiring diagram, I "cheated" a little and left the original engine ground from the NDP to the engine intact and added another parallel one from the NDP to the bus bar to the engine. It's worked just fine. The concept is to avoid multiple grounds (read more than one, but two's OK, more than that or lotsa little ones, is a no no...). All of these fancy-schmansy names, like bus bar and Power Post, are simply ways to connect and land wires to avoid multiple runs to another spot. Use what you like and what fits.

3. Yes, please see my discussion earlier, it's covered there, read it again. You're right, but it will work as Jim wired it if you run the boat the way I described. I'd move it to the banks.

I found the Mega fuses the best bang for the buck for fuses.