1987 MK 1 Electrical System Upgrade - Feedback Requested

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Stu Jackson

Quote from: Jon W on November 01, 2015, 08:58:17 PM


"Negative wiring doesn't make sense" - On the boat today the negative from the alternator is 4 AWG going to the newly added power post (part of harness upgrade). The busbar (also newly added with the harness upgrade) has 8-10 small gauge negatives and a single jumper from the busbar to the power post. The power post is connected to the engine with 4 AWG. I'm calling that "ships ground" in the schematic. What doesn't make sense?

Jon,

The Power Post in addition to the term strip, and the reserve bank separately connected to the engine ground.

Either use the PP or the term strip to "land" all negatives and run one wire to the ground.

Sorry I wasn't clearer before.
Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."

KWKloeber

Quote from: Stu Jackson on November 02, 2015, 12:18:47 PM
Jon,

The Power Post in addition to the term strip, and the reserve bank separately connected to the engine ground.

Either use the PP or the term strip to "land" all negatives and run one wire to the ground.

Sorry I wasn't clearer before.

Stu,

This is the setup that we talked about on the phone (putting a PP on the side of the stringer, and a neg busbar on the side of the engine compartment.  You gave me the measurements - 18" and 18" jumpers I believe.

Here's why we did it that way. 

Jon has #4 negs from the starter bolt, from the battery bank, from the alt ground.   You cannot have everything terminate at one place with the battery neg (i.e. on a starter bolt.)  Hence the negative power post (is 'power' and 'neg" a contradiction in terms?  :donno: )   and the batt neg runs right to the starter bolt where it should -- where you need the high draw connection for starting.  That bolt is jumpered to the 3/8" PP to pick up the #4 Alt neg.

But we needed a place to tie other lightweight negs (say, harness neg, bilge pump, fuel pump -- whatever negs Jon wants to have there.)  The rusty engine block shouldn't be used as a negative buss -- we need a good clean, easy access connection point.  You can't run lightweight cables (16, 14, 12, 10) to a 3/8" or 5/16" PP.   The terminals made for those light awgs and for large diameter posts are pure crap.  They bend, break and the darn rings are no larger for larger posts -- they use the same amount of material, but make the hole larger.  Hence, where you really need protection and strain relief, it is lacking.  I just won't do things that way. 

I considered the PP that has the ring of #8s terminals around the post -- but decided against it.  The post is quirky with all those small screws -- the heavy cable lugs need to be removed to access the #8s below if adding/servicing/removing a negative.  I just wouldn't do it that way / use that PP --  so I didn't want Jon to either. 

The PP I chose was a single post, and thus ran a #8 to a neg busbar (not a terminal strip as you say) and all the lightweight negs are on that negative bus, jumpered to the 3/8" PP.  It leaves an easy accessible point to tie any future negs to.

Does explanation that make more sense?

Ken

Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Stu Jackson

Quote from: KWKloeber on November 02, 2015, 07:10:14 PM

Does explanation that make more sense?



Yes, senior moment on my part. :D  It's been a while.  Thanks.
Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."

britinusa

Ken, a pic says a thousand words.

Just so that the language translation is out of the way(American to British  :?) , can you post (no pun intended) a pic of what you describe. ie. A pic of how it should be done.

:santa

Thanks.
Paul
Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

See you out on the water

Engine:M25XP

KWKloeber

Quote from: britinusa on November 03, 2015, 04:17:04 AM
Ken, a pic says a thousand words.

Just so that the language translation is out of the way(American to British  :?) , can you post (no pun intended) a pic of what you describe. ie. A pic of how it should be done.

:santa

Thanks.
Paul

Paul,

Basically how (I think) you already installed w/ the cables and appendages that I sent?

batt neg cable
    |
    V
STARTER BOLT
   |
4 awg cable
   |
   V
NEG POWER POST - 8 awg -> NEG BUSBAR - "light" negatives (harness, fuel pump, ...... etc)
   |
4 awg cable
   |
   V
ALT NEG POST

One remaining issue (as you know) is sometimes not having a good engine ground at the oil switch, temp sender, and hi temp switch.  Oftentimes it's related to corrosion on the ports and or bolts on the thermostat cap  By rights that should have all been 2-wire senders, not relying on the crappy grounds and threads.  I'm working on some kind of a kit to ground those directly.

Cheers
ken
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Jon W

Dropping down to a more detailed design level from the previous 30,000 foot level. Numerous changes. Still a work in progress, but getting closer. If folks have time to review the attached I'd appreciate the feedback.

Question - Can a MRBF type fuse like the ones used on the battery terminal be attached directly to the Alternator output post? Vibration make this not a good idea? Currently showing a midi fuse in a Blue Sea System holder in the engine compartment. Thinking how to simplfy/reduce the connections. Thanks for the help.

Jon W.
Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, 35# Mantus, Std Rig
San Diego, Ca

KWKloeber

Quote from: Jon W on November 03, 2015, 06:15:53 PM
Question - Can a MRBF type fuse like the ones used on the battery terminal be attached directly to the Alternator output post? Vibration make this not a good idea? Currently showing a midi fuse in a Blue Sea System holder in the engine compartment. Thinking how to simplfy/reduce the connections. Thanks for the help.

Jon W.

Why would you want a MRBF or MIDI there?

Ken
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Jon W

It is a 150A fuse on the alternator output. Moved it to the engine compartment to be closer to the source instead of the end of the wire at the battery box positive bus.  Jon W.
Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, 35# Mantus, Std Rig
San Diego, Ca

britinusa

I hope you guys keep going with this thread.

My daily reading of the forum topics is like attending class. I'm learning so much about  these concepts in general and about my boat in particular.

I'm curious. Is it your intent to gut the existing electrical connections entirely and rebuild, as per your diagram, starting from scratch, ie. Starting from just the equipment sans wire?

I presume you're going to label everything as per Mainesail's technique or at least something similar.

Paul
Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

See you out on the water

Engine:M25XP

mainesail

No fuse at alt end! The battery bank is your "source"... Fuse at batt end not alt end...
-Maine Sail
Casco Bay, ME
Boat - CS-36T

https://marinehowto.com/

Jon W

Hi Paul,
The plan started out as just a battery upgrade, but as I've learned more the project expanded. The project is now removing everything and then rebuild per the diagram.

Hi Mainesail.
Thanks, I have moved the fuse back to the battery box near the house bank. Speaking to Ken offline I now understand that my mistake was thinking the alternator is the source I'm protecting the wire from. The true source the wire needs to be protected from is the battery.

To others in the learning mode like me, here is what I learned in class today -

My 105A alternator, like all alternators, is current limited, meaning it can only put out its rating of 105A in perfect conditions. In reality it probably won't reach 105A. As long as the alternator output wire is rated for this current/amperage, you can't exceed the wire capacity with the alternator so no reason to put a fuse there. However, the fuse is needed at the battery side of the wire. The reason is if the alternator output wire were to get damaged/fall off the alternator terminal it could contact/land on the engine block. If that were to happen, it would create an electrical connection that the battery bank would try to feed. Being a 450A battery bank, all that amperage could flow in the wire which exceeds the rating of the wire and a potential for a fire now exists.

Jon W.
Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, 35# Mantus, Std Rig
San Diego, Ca

mainesail

#56
Quote from: Jon W on November 04, 2015, 07:25:55 PM
The reason is if the alternator output wire were to get damaged/fall off the alternator terminal it could contact/land on the engine block. If that were to happen, it would create an electrical connection that the battery bank would try to feed. Being a 450A battery bank, all that amperage could flow in the wire which exceeds the rating of the wire and a potential for a fire now exists.

Jon W.

Just a quick point of clarification.

Your bank is not 450A it is 450Ah. This means that when new, and fully broken in, it should be able to support a 22.5A load for 20 hours at 77F before hitting a terminal voltage of 10.5V. This is the 20 hour AMPERE HOUR rating. Deep cycle batteries are rated in ampere hour capacity and occasionally CCA, MCA and Reserve Minutes. Ah capacity is what we use for long slow discharges and CA or cranking amp ratings for starting the engine..

Amps is not the same as ampere hours. 1 amp for 1 hour = 1 Ah.

What we are protecting from, with fuses, is short circuit current. Short circuit current is even shorter in duration than CA, CCA (0F) or MCA (32F).

A 450Ah bank of GC batteries can easily deliver 1300 - 1600 cranking amps at 0F. CCA is a 30 second duration test performed at 0F and is cut off at 7.2V.

The short circuit current can be MUCH, MUCH higher and for a bank like yours could easily exceed 8000A. Many battery manufacturers do not publish "short circuit current" ratings but those that do show that this can be amazingly high. For instance a single Group 31 Odyssey AGM is capable of 5000A of short circuit current.

This bank is capable of 20,000A of short circuit current however it is only rated at 400Ah. This is why it is the battery bank we are afraid of!!



-Maine Sail
Casco Bay, ME
Boat - CS-36T

https://marinehowto.com/

KWKloeber

RC,

Is there a rule of thumb for short circuiting vs another measure of capacity, or simply do the math based on say the 20 rate?  While driving to nc last night I was thinking how to (err, "adjust") Jon's misnomer but didn't know how to estimate a s-c rate w/o knowing internal resistance.  In any event that kind of flow might instaneously weld a cable end to something.

Is there a general factor to estimate dead-short current assuming we know, say, the cca or 20-hour rate or..?  Or just do the math and ass/u/me a few second time period?

Ken
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

britinusa

Jon,
may I suggest a physical layout schematic also, similar to the schematics in the Catalina 34 Manual.

That would help identify the lengths of cable (and confirm cable sizing) but also identify where you need holes and panel locations.

Eximius' electrical wiring seems to be a hodgepodge that has evolved over the past 28 years, some of it appears to have been during a major electrical refit (includes a Freedom Inverter/Charger) plus the few things I have added/removed.

One common point made in many of the threads in this forum is about learning what you have installed and why it's installed (and that leads to understanding of how it should be installed). Having a physical schematic would help a lot.

Paul
Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

See you out on the water

Engine:M25XP

britinusa

Ken, I'm not so certain I would be concerned about the short circuit current. I don't want it to ever get up there.
The fuse would ensure that.

Paul
Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

See you out on the water

Engine:M25XP