Electrical System mods

[tmac]

I've read most of the info in the WIKI about improvements to the electrical systems, and I'd like to submit an idea for modifying my system to the group for comment, advice, ridicule, or whatever you can offer. 

Boat is 1988, with 4 Trojan T105s as house bank, and a separate starter battery aft of the engine. Right now, the boat still has the 1-2-Both switch, and then an older West Marine 50 A combiner was added, along with a Blue Sea On-Off keyed switch for managing the starter battery located aft of the engine compartment.

I know there are different schools of thought, one which promotes keeping the starting battery as a "reserve", and using the house batteries to also start the engine.  My concern with that is if you don't regularly use the "reserve" battery, how certain can you be that there's nothing wrong with it?  In my truck, I've had batteries that "seemed" OK voltage wise but couldn't crank the engine over.  The way I'm looking at it, if I use the reserve battery as a regular starting battery every time, I'm going to quickly recognize when it isn't healthy, and then I can fall back on my house bank in that one case to get me home.  Also, I've never liked 1-2-Both switches and would like to eliminate mine.

With that in mind, I've set out to separate the two banks in a different way.  I found an interesting switch at Blue Sea that is a dual circuit "On-Off" switch (#5511e).  It has an optional position allowing combining the two circuits, but for the most part it is used simply to turn on or off both circuits at the same time, but keeping them isolated from each other. Then for charging, I'd use Blue Seas m-ACR to combine the charging cycles. 

This seems to me to be a simple solution and it would allow me to eliminate the 1-2-Both switch (and its inherent operator errors).  I drew out a simple diagram in MS Powerpoint and attached it to this post (I hope...)  (Yes, I know there should be fuses, etc.  I just kept this diagram very simple for this discussion.)
Thoughts?  Suggestions?  Any reason this wouldn't work?

[Stu Jackson]

Tom,

That BS DC switch is a disaster just waiting to happen.  Do NOT use it. 

The worst thing you can do is to combine a bad bank with a good one. 


That's all that BS DC switch can do.  Wired properly the 1-2-B switch, as a USE only switch, with all charging going to the house bank, is preferable.  You already have the combiner for charging.  You already have a 1-2-B switch.  The ES101 topic covers all the wiring for it.

That's Maine Sail's conclusion, too.  You can read all about it here, from the Electrical Systems 101 topic, which is a great resource in addition to those in the tech wiki.

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
https://forums.sailboatowners.com/index.php?threads/darn-agm-batteries.133773/

[Jon W]

If you've read the write-ups in the Tech WIKI, you've probably read mine. After 6 years, I recently had the exact problem you describe with my reserve battery. Voltage good, but couldn't start the M25XP. I found it just before my next trip because I alternate between the house bank, and reserve battery to start the M25XP.

You should have the alternator output go directly to the positive post of your house bank, not the switch. Connect your fused combiner to the same house bank positive post then to your start battery. FWIW - I kept the 1-2-Both switch because with the alternator output going to the house battery positive, the 1-2-Both switch is removed from the charging circuit. The 1-2-Both switch is now only a bank selector switch, which removes the possible error you referred to.

I'd urge you to add an "Always On" buss now for future upgrades. I've added AIS, Last Watch II, and Solar panels over the years. The "Always On" buss simplified connecting them into the electrical system. My AC charger, and Distribution Panel come off that buss as well.

[tmac]

Stu -
Wow - sorry!  I seem to have hit a nerve!  I have to admit that I only just started thinking about this project yesterday, so I guess I'm glad I posted my question and didn't waste time on a bad idea.  I confess I did have a momentary thought about adding a way to turn off one bank after combining, but I didn't pursue it.  After reading the link you provided, I now see I should have pursued that idea further.  But it appears that the way my system is set up now is the way to go. 

[tmac]

Jon,
Thanks for the recommendations. I like the idea of the buss bar. Yes - my alternator is directly wired to the positive post.  The previous owner spent a lot of time here on this forum, and he followed many of the recommendations.  I've only had the boat since September, and had to wrap it up for winter almost immediately, so I haven't had the luxury of spending time going through the boat's systems.  I'm in the mode of sitting at home, wishing I could work on the boat, but being stuck with just fantasizing about what I'll be doing next spring.  I have to guard against trying to "fix what ain't broke!"

[tmac]

Is there a way to just delete this entire post?  I see now that I missed several very pertinent sections in Electrical 101 that speak to this specific issue and I need not have bothered anyone with my question. I know you must tire of new owners asking questions about stuff that is well documented in your archives. 

[Jon W]

Your schematic looks like the alternator output goes to the #2 position on the switch.

No worries. Reading the 101 topics, Tech WIKI, and Tech Notes will answer a lot of questions and probably raise a few. With so much information available from different people, written at different times you're bound to run into contradictions. We're happy to help, and good luck.

I haven't done it so am guessing, if you click the "remove" link on your original post, it's gone.

[Noah]

I have a bit of a different system:
I have a house bank (4 T105 6v and an engine bank, 1 group 24 12v). I have a Blue Sea on/off switch on each bank, as well as a combiner switch (with removable safety key). I also have a multimeter and Smart Gauge on my main panel that measures voltage and amps (in and out of house bank). My start battery is charged by an echo charger from the house bank. I can shut off either bank. In the case where my engine bank ever "died" I can shut it of and turn on the "combiner" switch and start off of my house bank. In the case of house bank "failure" I can shut it off and turn the combiner key/switch and use my engine bank. Fortunately, I have never had to do this in over six years the system has been in place.

[Kyle Ewing]

Tom,

I wired my 1990 in a similar manner as you propose, including On-Off-Combine switch, with some key differences:
*  Two banks of golf cart batteries wired to the factory 1-2-both switch.  I always turn the switch to both to have one large bank.  If a single bank fails I can easily isolate by switching to either 1 or 2.  This also allows me to measure each bank's voltage independently when switch is off so I know if one is developing a problem.
*  The starter battery is behind the engine.  I have the On-Off-Combine switch you describe under the head sink.  When I turn on the starter switch I ALWAYS open the engine through-hull and ALWAYS close when switch is off.
*  The alternator outputs power to the house bank.  The starter battery is charged through an Echo-charge.
*  If start battery is low I can switch the battery switch under sink to "combine".  I can disconnect the start battery with a circuit breaker near the battery if the battery ever develops an internal short.
*  Start battery will power house loads when under sink is set to "combine".

With my setup the starter battery is used every time I start the engine so I know it works.  House loads are isolated and charged directly by alternator.

This setup has served me well for many years.  It worked as expected the only time my start battery was low (Echo charge failed so battery wasn't charging, fuel pump uses power).  I'm able to power house loads when house battery is disconnected (i.e. when replacing batteries or cleaning terminals).

In hindsight a 1-2-both switch might be better than the On-Off-Combine switch, however as Maine Sail says in Stu's link, make sure it's the right fit for you.

I wouldn't delete your post.  It may be valuable to someone who's considering the same switch.

[tmac]

Thanks for all the input guys!  This board continues to amaze me with the depth of experience and the willingness to help.
Sounds like I was not entirely wrong in my thinking, but needed a few course corrections.

Noah - what CAD or diagramming software do you use?  Next spring I want to extensively document the wiring on my boat and uncover 33 years of improvements, and diagram everything like you did, so that when I'm dead and gone the next guy will know what's what. 

[Stu Jackson]

Tom, I don't know what Noah used, but we discussed options here:

https://c34.org/bbs/index.php/topic,4821.msg29037.html#msg29037

There may well be others, which we could add to that list.

There has been a relatively recent trend to add actual pictures of equipment to wiring diagrams, AFIK spurred by Maine Sail's diagrams for his client.

[Jon W]

Tom, I used Visio 2007 to make schematics of most of my electrical systems. Visio is more for work flow, but worked well creating wire diagrams. Not the only tool available, but it's easy to learn, use, and you can save in multiple formats like the PDF and JPEG I attached here. I also use Excel to document the wire details.

I make color prints of all schematics, laminate them, and keep on board along with the electronic versions on my laptop. Examples attached for reference

[Noah]

I have a graphic design background, so I used my existing "tools"; Adobe Illustrator and/or Adobe InDesign. No cad or engineering features, just computer aided vector shapes/lines, etc.

[Admiral_Swellson]

I've been using draw.io, which is freeware. It works ok, price is right. Visio is better if you want to part with the money.

https://www.diagrams.net/