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Old 04-21-2017, 07:29 AM   #21
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I am going to have to do some thinking about ways to simplify this and maybe get more utility out of the all that weight.
And that is exactly CMS's point. Why lug around all that dead weight just to start each engine when you can do the same task with less weight and leverage the remaining as a usable house bank?

That is why I was so dumbfounded when I started tracing and discovering the DC system on our relatively new (2000 model) US built boat. It was obviously designed for A) a marina-only boater B) a company that just got 8D batteries by the pallet load. I mean it really made no sense.

If memory serves, it had three 8D banks. Two banks were selected by a 1/2/Off/Both switch to, basically, everywhere. Then there was just an On/Off switch that just added the third bank into the mix. I expected more from them... Oh well. It's all better now.

I don't think I have a layout of the original layout except for maybe a pencil drawing, but I will snoop around and see what I can find and post it.
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Old 04-21-2017, 08:37 AM   #22
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Another reason to connect alternators directly (however fused) to the house bank.

So if connecting directly to the house bank. (Lets assume a 65 amp alternator) do I need a 65 amp fuse?
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Old 04-22-2017, 08:54 AM   #23
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Another reason to connect alternators directly (however fused) to the house bank.



So if connecting directly to the house bank. (Lets assume a 65 amp alternator) do I need a 65 amp fuse?


No, it need to be a bit higher than that, but I can't pull the formula from my head right now. 20%? 30%? Buffer? Look up the formula or maybe CMS will chime back in. But be clear about one thing... the fuse more protects the wire and not the source. :-)
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Old 04-22-2017, 09:49 AM   #24
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This is mostly how I did mine, replacing 2 banks of 8Ds that were outboard of the mains. (Good for weight distribution, but terrible for engine maintenance.).

Not shown are the isolation transformer and associated breakers I added and a second 4/0 feed from the house bank to the main panel. I currently have one Group 31 to start all diesels (may add another) that can be substituted with the house bank.

I may revisit how the windlass is powered--currently off the house bank--and change to the start bank, the way Al has it, since it will only operate when the engines are running.

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Old 04-22-2017, 11:16 AM   #25
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Another reason to connect alternators directly (however fused) to the house bank.



So if connecting directly to the house bank. (Lets assume a 65 amp alternator) do I need a 65 amp fuse?


Others are much more knowledgable than I. Generally, anything connected to the battery should be fused very close to the battery (isn't it supposed to be within 7"?). The purpose of this fuse is to protect the wiring in the event of a short. The fuse is sized based on the wire size, run length, and whether or not it runs through the engine compartment.

I don't know whether that also holds for charging connections such as from a charger or alternator.
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Old 04-22-2017, 11:58 AM   #26
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My KISS Electrical AC and DC Profile:

- Two Perko Switches - First One "On/Off" ... Second One "Off, 1, All, 2"

- Four Group 31, LA, Parallel Deep Cycle - Used for House Bank and Twin Engine Starter Batts: Charger activated by shore power, or gen set. Stbd engine alternator also does well.

- One Group 27, LA for Gen Set Starter Batt: Charged by gen set alternator and small solar charger.

- One Isolated Group 27 Starter Batt [for emergency]: In its own black box with 1 amp charger activated by boat's 110 breaker switch during shore power or with gen set running. Remains well charged. Also aboard is long good gauge jumper cables if needed.

When aboard boat at dock: I keep shore power plugged in [we don't usually sit at dock but maybe one evening getting ready to cruise] First Perko to "On" and Second Perko to "All" with batt charger on and 110 breaker on.

When Anchored out: Gen set usually runs 1 to 1.5 hrs mid morn and same mid eve... with batt charger breaker on.

When off boat: I unplug shore power and isolate house/starter bank by keeping both Perkos "Off". As well as all breakers "Off". This technique greatly eliminates galvanization/electrolysis... because, no stray currents from AC or DC attack metal parts.

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Old 04-23-2017, 10:07 PM   #27
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House battery for everthing?

See my thread House battery for everything? Trying to rework old boat and understand wiring. don't know if I have battery isolators or combiner or ACRs. .ust trying to make it work with 3 weeks left
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Old 04-23-2017, 11:14 PM   #28
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See my thread House battery for everything? Trying to rework old boat and understand wiring. don't know if I have battery isolators or combiner or ACRs. .ust trying to make it work with 3 weeks left
Very best luck! All I can recommend is KISS as possible! - Art
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Old 04-24-2017, 10:56 AM   #29
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Lots of helpful thoughts, thank you all!

I've been working my way toward this problem; plenty of other stuff to do before the shrink wrap comes off and the boat's launched. The best thing, so far, for this problem is that I've gotten rid of the delaminated 1/2" plywood ER floor, with the awful aluminum diamond plate and replaced it with 3/4" pressure treated CDX plywood and 1/2" cleanable vinyl antifatigue mat (from McMaster-Carr). I can now tolerate being on my knees down there, and the house bank batts now sit firmly level.
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Old 04-24-2017, 11:19 AM   #30
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Create a Switch Configuration That Can:[/B]

*Allow Bank 1 to be used for both starting and house loads in an emergency

*Allow Bank 2 to be used for both starting and house loads in an emergency

*Allow full isolation of the bank not being used in an emergency

Starting a motor, even massive ones, barely uses 0.1% - 0. 5% of your start batteries capacity, so why lug that 99.5% + around, just waiting to use it , and then you never do?

This dead lead is put to far better use as live lead in the house bank.

Charging Sources to House -
With a twin engine set up feed all charging sources to house, with the exception of the smallest alternator, for the start battery. Place a VSR/ACR/Combiner between the banks and then both alternators contribute current to the charge bus where it is most needed. This yields optimal charging performance and gives a very simple system.
Wow! This is exactly what I have on FlyWright. Although my 55A shore charger capacity falls short of CMS recommendations for a 660AH bank, its peak 13A load is the max my Honda eu2000i generator. Iit works well in my fishing and cruising profiles where my Balmar 120A alternator carries most of the charging duties. I feel like my boat electrical system configuration has been validated with an imaginary CMS stamp of approval!

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Old 04-24-2017, 04:26 PM   #31
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Wow! This is exactly what I have on FlyWright. Although my 55A shore charger capacity falls short of CMS recommendations for a 660AH bank, its peak 13A load is the max my Honda eu2000i generator. Iit works well in my fishing and cruising profiles where my Balmar 120A alternator carries most of the charging duties. I feel like my boat electrical system configuration has been validated with an imaginary CMS stamp of approval!





I felt kinda validated too, although, I am not 100% into his design. And I too am woefully short on charger. 60A for 900+ AH. I am not sure my overall system could support a high-amp charger.
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Old 08-28-2017, 02:30 PM   #32
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Latest news on my battery charging 'system'! Amazing!

The two 'off, 1, both, 2' battery switches which would appear to be related to the adjacent engine, may well have been once but were not up to last week. Get this; laugh and/or weep: the right switch was wired: stud 1 to the port engine starter (and therefore to the port engine's battery) with AWG 2; stud 2 to the right engine's battery with AWG 2 (it was then connected to the right engine's starter), and an AWG 2 jumper from the output of the right switch over to the left switch. The left switch was then wired with AWG 2 to the house bank. Therefore, with this unlabeled, and apparently-known-only-to-a-PO, arrangement, one could charge the house bank with either engine or with both at the same time.

I was forced to delve into this when the port engine would not start and the left battery switch would turn freely (w/o the customary 'click' to each position). I naturally, but wrongly, decided that the non-start was due to the switch. Turned out that a tank installer had lain on the wire in the ER and physically broke the switch.

I continued my investigation and found that the 'off, 1, both, 2' battery switch at the 12v panel actually had no voltage available for the #2 position. This was easy to discover with the voltmeter on the panel, but hard (still not sure) to follow from within the space under the helm and behind the 12v panel.

I then discovered an AWG 1 conductor, with red tape, curled up disconnected under the starboard engine's battery. I can only surmise that there were once two house battery banks but much of that wiring is missing (I have not yet found an abandoned conductor corresponding to a ground, or any other heavy conductors); I could therefore surmise that each engine could charge its own start battery and a house bank.

Unless I'm truly as dumb as my performance in 'Electricity and Magnetism' at McGill would lead one to believe, I suppose that the battery switches at the engine panels could control which bank of engine+house batteries would start the engines. There would be a lot of unfused large conductors wandering around and there is no sign of any of that remaining.

Means that I now have no way to charge the house bank with either engine. Also means that I'm free to (steal a) design a new system.
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Old 08-29-2017, 01:32 PM   #33
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Glad you're getting it figured out. The last three used boats I've run all had some very odd-ball wiring for their battery banks. It seems very few really understand what they're doing.

With twin engines, you have a lot of flexibility to KISS. I'm not opposed to battery switches, personally. I find them more simple, understandable and functional than some of the crazy things I've seen done with combiners and isolators.

On my boat the house bank starts one engine, and a dedicated starting battery starts the other. The engine with the house bank has a high-capacity, externally-regulated alternator. But I have switches that allow me to swap these if one alternator fails.

I don't like the idea of combining the house and starting banks for charging. They are likely to be at very different states of charge, and are configured with very different batteries.

On shore power or genset, my 100A charger is connected to the house bank, while the starting and genset banks share a 30A, two-way charger. This way each bank has its own dedicated charging circuit.

Underway both the house and starting banks are charged, or kept topped off, by their respective alternators.

The genset starting bank is only connected to the genset. It's sort of a third back-up to the the other two banks.

This is truly a simple configuration. Normally, I touch none of the switches all season, but in a pinch I have lots of options.
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Old 08-30-2017, 05:25 AM   #34
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"I don't like the idea of combining the house and starting banks for charging. They are likely to be at very different states of charge, and are configured with very different batteries."

This is true , but it hardly matters.

If the alt is working the out put to even 75% discharged batts will soon be above 12.8 .

At 12.8 the starts voltage will be held and not discharge into the house bank.

At any voltage over 12.8 the starts may be charging a tiny bit to make up for the current used for the start.

No worries , no hassles if there all the same style batt like wet lead acid.
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Old 08-30-2017, 10:13 AM   #35
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"I don't like the idea of combining the house and starting banks for charging. They are likely to be at very different states of charge, and are configured with very different batteries."

This is true , but it hardly matters.

If the alt is working the out put to even 75% discharged batts will soon be above 12.8 .

At 12.8 the starts voltage will be held and not discharge into the house bank.

At any voltage over 12.8 the starts may be charging a tiny bit to make up for the current used for the start.

No worries , no hassles if there all the same style batt like wet lead acid.
Bingo!!

More batteries on boats are charged in parallel than by any other means. I have start/reserve banks out there that have gone around the planet twice charged in parallel via VSR/Combiner/ACR's for thousands & thousands of hours of charging. So long as charge voltages are the same for each bank parallel charging is basically a non-issue.
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Old 02-08-2018, 03:08 PM   #36
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And that is exactly CMS's point. Why lug around all that dead weight just to start each engine when you can do the same task with less weight and leverage the remaining as a usable house bank?

That is why I was so dumbfounded when I started tracing and discovering the DC system on our relatively new (2000 model) US built boat. It was obviously designed for A) a marina-only boater B) a company that just got 8D batteries by the pallet load. I mean it really made no sense.

If memory serves, it had three 8D banks. Two banks were selected by a 1/2/Off/Both switch to, basically, everywhere. Then there was just an On/Off switch that just added the third bank into the mix. I expected more from them... Oh well. It's all better now.

I don't think I have a layout of the original layout except for maybe a pencil drawing, but I will snoop around and see what I can find and post it.
I think you would find the original buyers (and the buying market in general) want the 8Ds.
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Old 02-09-2018, 05:40 AM   #37
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"I've got twin Perkins with a group 31 deep cycle battery for each"

Just wondering why you chose a deep cycle battery to start an engine?

Gp 31 starts are common as dirt , Gp 31 deep cycles are harder to find .
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Old 06-26-2018, 09:25 AM   #38
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I have completed replacing nearly all the battery wire on our '84 FuHwa with its twin Perkins 6.354s. I used the Blue Seas wiring diagram for three banks, three battery switches and two ACRs. This layout allows me to choose a variety of the battery banks to start the engines, isolates a depleted starting bank, charges the house bank with engine alternators. I have also replaced the 110v battery charger. "Nearly all" means that I have not replaced the anchor winch leads nor the genset leads (both are untinned welding cable).

I have opted to fuse all the battery hots with MRBF post-mounted fuse holders. Adds up to quite a collection since the charger requires three and each lead of an ACR requires one. And I fused the three banks. Total of 9. All the wire is 1/0 AWG except the charger's which is 6 AWG. Capacity of the 1/0 AWG is 285 amps.

I (rather dumbly) installed a 100 amp fuse on the house bank and 200 amp fuses on the starting banks. The 200 amp fuse blew when attempting to start an engine, and adding idiocy to dumpth I proceeded to blow the other two bank's fuses.

I had read that the starter motor ought to draw 160 amps. Apparently not. What size fuses should I now buy (not wishing, at $18. a pop, to experiment)? Easiest answer is to buy 300 amp, which is the largest that's available and overloads the wire a smidge; otherwise 250 which is the next size down.
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Old 06-26-2018, 10:09 AM   #39
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The starter motor might draw 160 A spinning the engine, but it is typical of starter motors to draw 50-100% more for an instant at stall (right when they engage). If the engine is slow to start, or the battery a bit low, the starter will draw more amps. I'd worry about the reliability of a 250 A fuse if a 200 A blew immediately. Ideally you'd go to bigger wire along with the 300 A fuse, but I'd sleep fine with a 300 A in there anyway.

1/0 seems kind of small for starter cables, even on a small engine. The 2 liter engine on my sailboat is wired with 2/0, the 5.9 liter engine on the powerboat is wired with 4/0 for the start circuit.
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Old 06-26-2018, 12:12 PM   #40
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1/0 seems kind of small for starter cables, even on a small engine. The 2 liter engine on my sailboat is wired with 2/0, the 5.9 liter engine on the powerboat is wired with 4/0 for the start circuit.

Interesting re wire sizes. This boat has had the 38mm / 1/0 AWG wire since '84. Our sailboat had 1/0 for its Yanmar 3GM30 and the house bank but the wire size dated (at least) from when the PO had a 100 amp Balmar alternator installed. This boat has the same size house bank as the sailboat(!).
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