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modified 2-bank topology & switches layouts

Discussion in 'Musings With Maine Sail' started by John61CT, Jan 11, 2017. Add this thread to a FAQ

  1. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    Rather than polluting MS's fine "optimal switches" thread http://forums.sailboatowners.com/index.php?threads/1-both-2-off-switches-thoughts-musings.137615/

    here's my separate one for discussion of variations, whether speculative but sound, or noobie ignorance remains to be seen, all feedback welcome.

    > The three switch configuration has little to do with "combining banks" it is all about isolation, redundancy and the ability to "cross-connect" either bank to power and start the entire boat in an emergency

    >If you want the three-switch configuration wire it properly with three switches.

    =========
    my modified Three ON/OFF Switch configuration

    http://i.imgur.com/tJQcamJ.jpg

    The Blue Seas Dual Circuit Plus' OFF disconnects BOTH batteries from their respective Load circuits, so in normal usage the lower 0/1 switches stay ON, only the top DCP switch gets turned on and off.

    Each bank can be independently isolated if needed, either one can feed either House panel or crank/engine circuits.

    Note the Alt directly attached to Primary (house) "always on buss"

    Smart VR sensors on both batteries and Alt temp.

    Sorry for the crude sketches & handwriting, all I got's my phone ATM.

    Question: combiner/echo unit should be below the switch, not above it, correct? (if so, see next diagram for correction)
     


    Last edited: Jan 11, 2017
  2. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    >If you want a 1/2/BOTH install a 1/2/BOTH...

    This is not KISS in layout, but perhaps more self-evident for the prematurely demented captain or even less experienced crew / family members?

    2 selectors, 2 ON/OFF
    http://i.imgur.com/SO7rVbj.jpg

    Each of the two main load groups

    A house "accessory" loads, non-essential for safety or navigation, etc

    B "engine/crank/nav/running lights/radio" AKA "boat loads"

    can select either bank, or be turned OFF.

    These are the only switches normally used, and A=2 & B=1 will be VERY obviously labeled as "normal" usage, their opposite, combined & OFF only for anomoly/emergency use.

    The bank isolating switches only to be used for the latter or servicing, located near the batteries.
     


    Last edited: Jan 11, 2017
  3. Stu Jackson

    Stu Jackson

    Joined Feb 26, 2004
    19,183 posts, 295 likes
    Catalina 34
    US C34 San Francisco
    Nope, that's NOT what it does.

    Spend some time looking thru that Electrical Systems 101 link I gave you on the other topic.

    OK, I'll save you some time looking for it:

    AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
    http://forums.catalina.sailboatowners.com/showthread.php?p=848465&highlight=darn agm


    You really should read the stuff first and you'll see why not.

    Sorry about the underlining here.

     


  4. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    Will do Stu.

    Note the bottom two 0/1 switches in this first "three switch" diagram, one for each Bank.

    My intention (sorry I didn't state explicitly) is for a bad/really dead bank to be isolated, the Combine slot of the top DCP switch becomes "both loads can use the remaining good one".

    I understand that switch-combining good bank with bad can be fatal, in my original meander I tried to stay away from that.

    I think maybe my second "four-switch" sketch makes this issue more explicit as a "Load uses which" switch, separate from the real bank isolation functions, at the price of some redundancy.

    Thanks for that though, and if I *did* actually misunderstand Blue Seas' docs on how the DCP switch works, do please let me know, I'm pretty sure I understood it?
     


  5. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    2,781 posts, 156 likes
    Starwind 27
    US Allamuchy Barnegat, NJ
    I'm a little confused about your goals, but I'll take a crack. You want to keep House bank and Start bank separate and you want the ability to have both banks on simultaneously? Your start bank must also serve as an auxiliary bank with limited house loads, so you want the ability to isolate Start bank rather than combine the 2 banks?
    I have a DCP set-up, as well, because of my desire to have 2 separate banks ON at the same time. (I was sold on the opinion that it is better to separate the Start Batt from the House bank.) The common complaint is that it does not provide an opportunity to isolate 2 banks and provide redundancy. It can only combine 2 banks (an undesirable condition) for emergency Start when the Start batt is disabled or use of the House bank when the House Batts are disabled. So I understand the complaint and simply take the chance that I will never truly need the redundancy that the 1/2/BOTH switch provides.
    The solution that you present with the 2 ON/OFF switches linked to the Combined position on the DCP switch looks like an elegant solution that makes the DCP switch more versatile than the single 1/2/BOTH switch. Perhaps there is a negative to this solution, so I am interested to hear.
    Stu's link is about the inability of DCP to provide isolation in a stand-alone configuration. The additional switches appear to make it feasible to make DCP work in isolation - relatively simple and effective solution. What's wrong with it?
     


    Last edited: Jan 11, 2017
  6. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    MS from "Darn AGM"
    >Even a failing bank can support a 2-6 amp draw for a while and "appear" to be fine. This is an actual benefit of starting your motor off the house bank. By using the house bank for starting loads it lets you know early that your house banks capacity is getting weak.

    Both my layouts and both in MS' 1/B2/O original post
    http://www.pbase.com/mainecruising/image/154153780.jpg

    and
    http://www.pbase.com/image/155636682.jpg

    allow the engine cranking to be fed from either bank at will.

    Seems like routinely switching to "the other one" every once in a while would be good practice, maybe even part of a scheduled maintenance checklist when cruising.

    My theory is that my four-switch layout allows for stuff like that with minimal head-scratching, needing to read a posted checklist etc. Especially under duress!

    Big obvious labels, as intuitive as possible is key for idjits like me. . .
     


    Last edited: Jan 11, 2017
  7. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    Yes, normal config is where I show the switch settings, engine uses Starter (reserve) bank, House uses Primary.

    >Your start bank must also serve as an auxiliary bank with limited house loads

    Well not "must" but "possible, might do that if something put on the Accessories (house) panel turns out to actually be necessary for getting back to safe harbor". My intention is to use it for cranking only much as possible, not when the kids want to keep on playing Animal Jam.

    > so you want the ability to isolate Start bank rather than combine the 2 banks?

    Yes, very wary of Combining, but can see scenarios where it may (hopefully never) be needed.

    >Perhaps there is a negative to this solution, so I am interested to hear.

    Me too :cool:

    Thanks for the feedback!
     


  8. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    2,781 posts, 156 likes
    Starwind 27
    US Allamuchy Barnegat, NJ
    The four-switch sketch is way too confusing for my simple brain. I'm left wondering what is the goal. If the goal is simply to accomplish the same as can be done with the 3-switch solution with DCP, then I can see my preference.
     


  9. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    MS, same "Darn" thread
    > So all I need to do in the event of a shorted bank is to remove the house bank neg, 15 seconds with a wrench, and turn the 1/BOTH/2/OFF to BOTH. Now the house is off line and the alt current flows directly to the start battery via BOTH. Disconnecting the banks neg lead is often far easier than the + connections.(Edit: end MS quote here)

    In both my layouts, there is a Both in the top switch, and an Off/isolate for each bank to accomplish exactly that.

    I like the logic of this post there http://forums.sailboatowners.com/index.php?threads/darn-agm-batteries.133773/page-2#post-891581 and AFAICT I think both my layouts (and both of MSs') have all those bases covered.

    The last scenario of one shorted bank preventing the combining gizmo from working to get Alt charge back to Starter batt, seems a real outlier to me, but many of these do have a manual combine, or put the Alt above or on the C of the isolating switch.

    Or use a jumper cable, amirite? :cool:
     


    Last edited: Jan 11, 2017
  10. Stu Jackson

    Stu Jackson

    Joined Feb 26, 2004
    19,183 posts, 295 likes
    Catalina 34
    US C34 San Francisco
    After all these years, one would think that we all understood that is not a good idea (UNLESS a charging source is present).

    And, Scott, IIRC from the past, you had some good reason to do what you did. IIRC you use your boat similar to a runabout, which Maine Sails says the DCP switch is OK for. Most folks run their sailboats differently than you do.
     


    Last edited: Jan 11, 2017
  11. Stu Jackson

    Stu Jackson

    Joined Feb 26, 2004
    19,183 posts, 295 likes
    Catalina 34
    US C34 San Francisco
    If you turn the two I/O switches off the combiner won't work.

    The DCP switch only has ONE output, not two.

    Even a 1-2-B switch has only three studs for wire connections on the back: C, 1 & 2. C is the common post that feeds the starter and the house electrical panel. There are four positions on a switch: 1, 2, combined and off. Posts and positions are two different things.

    This is covered in great detail in the Electrical System 101 topic I sent you.

    The sixth topic on that thread is this one:

    OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101
     


  12. Stu Jackson

    Stu Jackson

    Joined Feb 26, 2004
    19,183 posts, 295 likes
    Catalina 34
    US C34 San Francisco
    How is disconnecting a wire easier than simply turning a switch?
     


  13. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    It isn't, that was the end of MS' scenario, mine uses a switch.

    Sorry that wasn't more clear.
     


  14. mitiempo

    mitiempo

    Joined Sep 28, 2008
    921 posts, 7 likes
    Canadian Sailcraft CS27
    Ca Victoria B.C.
    John

    Both the configurations you link to in posts #1 and #2 are over complicated. You would have to turn 2 switches to accomplish anything. Too many connections as well.

    Easiestr solution is 3 simple on/off switches - Blue Seas 6006 is a good choice. One for start, one for house loads, and a crossover wired so you can use either battery bank for either purpose without combining. In my opinion this combination cannot be beat for simplicity and ease of use.
     


  15. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    Yes my three-switch with DCP is definitely a more streamlined diagram, but with good user labelling I think the four-switch may be easier for a newcomer (or early-dementia) to understand, no cheat sheet needed.

    I think. . .
     


  16. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,176 posts, 243 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME

    The DCP with two ON/OFF switches is a fine alternative to three ON/OFF's.. I often fix DCP installs by adding two Blue Sea mSeries ON/OFF's. I tend to make them "hidden" switches near the physical batteries so only the owner can mess with them...

    The other diagram... Not so KISS....
     


  17. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    "On" as in "Starter tied in to engine / essential circuit Loads, available for cranking" AND "Primary (house) available to carry Accessory Loads"

    But not combined except for the Starter getting topped up once the Primary /House /Accessory circuit hits the high voltage threshold.

    Otherwise the two are completely isolated unless I throw the switch to Combine, which personally I wouldn't do without isolating the bad/dead bank first.

    Isn't all that OK?
     


  18. John61CT

    John61CT

    Joined Jan 7, 2017
    49 posts, 1 likes
    beneteau 36
    US eastern US new london
    Excellent, answers this from the OP then:

    >>Question: combiner/echo unit should be below the switch, not above it, correct? (if so, see next diagram for correction)

    Answer: yes, below the bank switches is correct
     


    Last edited: Jan 11, 2017
  19. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,176 posts, 243 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME
    The DCP has two inputs, house & start and two outputs, house & start...
     


  20. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    2,781 posts, 156 likes
    Starwind 27
    US Allamuchy Barnegat, NJ
    I'm not sure why you say DCP has only one output. There are 4 studs on the back. There are 2 Batt inputs and 2 outputs (house panel and starter). The 1/2 BOTH switch has just 3 studs. There are 2 Batt inputs and just one common output.
    The 2 outputs on the DCP is the advantage of the DCP? No? The disadvantage of the DCP is the inability to isolate the banks for a common output. The additional switches solve that disadvantage, no?
     


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