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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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Old 09-09-2011
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Question Best way to connect all charging sources to the house bank without making spaghetti?

Hello! Thanks again for the continued help!

This is part of the ongoing electrical refit on my Oday 37, for what that's worth to you expert types.

Following current wisdom, I'm moving all charging sources to the house bank, and then installing an Echo Charger to handle the start bank.

In the planning process, however, it's becoming clear that just connecting stuff to the battery terminals isn't an option. Here's what I'll have wired to the positive terminal of the house bank:
-Xantrex 20Amp TruCharge, powered by shore power (when available)
-Engine Alternator
-Eventually, Solar Power (that's on the next-month list)
-Eventually, Wind Power (that's on the 3-6 month list)
-Echo Charge unit
-Bilge pump (not directly.. through a circuit breaker)
-Eventually, Backup bilge pump (also not directly, as above)

So, really, it's just not an option to wire everything to the battery terminal, right?

I plan to use those terminal fuses (these guys: Blue Sea Terminal Fuse) quite liberally. I figure one on every battery (at this point, there are just two group 27's for the house and one group 27 for the start bank).

What I'm wondering is, why not make a short run from the positive terminal of the house bank to a bus bar located right there in the battery compartment (on this boat, said compartment is HUGE). So I'd use, say, a 150A fuse at the battery terminal itself, then run a #1 AWG wire from the battery to the bus bar.. maybe 18" to 24" away. On that bus bar, I could use additional terminal fuses on each terminal. So all of the above items would be individually fused right on the bus bar.

(The exception to that would be the Victron battery monitor, which could easily be attached to the actual battery terminal, even before the fuse, as I understand it)

So what I would end up with is a large bus bar right next to the battery, and every post on that bus bar would have a Terminal Fuse of some size (the actual rating of the fuse can be changed easily and at no extra cost). Coming off that bus bar would be:
-All charging systems, each on their own post and fused appropriately
-A 1/2/both/off switch, which would then lead to the DC panels normally
-The bilge pump(s) (located here so that they are always on, but fused so they can be disconnected)

If all of that makes sense, would it also make sense to mount a bus bar for the negative stuff? It wouldn't be fused individually, of course, and would be mounted ahead of the shunt for the battery monitor. This bus bar could then take all the negative leads and connect to the house bank neg terminal.

Seems like this would make for easier trouble shooting down the road?

And, after all that text, I apologize if I just re-invented the wheel and all this is standard already. The books I have (Ed Sherman's and Wing's) seem to gloss over the actual nuts and bolts of connecting everything to the house bank.
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CapTim,

No, you have it just right! That would work just fine.

Only comment is that those MRBF fuses and holders ain't cheap. Once you've got the main fuse (150A in your case) on the battery bank, you could go with other types of fuses and breakers if you like.

Also, you don't need an MRBF fuse on every battery. I assume you're talking about the house battery bank, in which case the batteries would be in parallel if they're 12V or series if they're 6V (e.g., golf carts). You only need a single fuse located at the positive take-off terminal on one of the house batteries. Others battery terminals can be connected directly.

You do NOT want to fuse the negative battery cable to the battery bank. Exception: if you're wiring a SSB radio, it's good to have 30A fuses on both the positive and negative leads to the radio, but these would be attached to the bus bars in your example, not to the battery bank itself.

Bill
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Good to know I'm on the right track.. thanks!

Even better to know I can save some money.. I'm not a proud man, I'll take what I can get in that regard.

Could you recommend a fuse that would be appropriate between, for instance, the positive bus and the alternator? I feel like something along the size of 2-4AWG would be appropriate (the run will be about 4 feet one way) with a 100 or 125 amp breaker.

It seems like blade style fuses would be the easiest in terms of carrying spares, identifying proper sizes, and east of replacement. But I haven't seen a way to just 'wire up' a fixture for one to mount in?

Or would you use some sort of an inline fuse, rather than something hard-mounted to a solid surface? It seems like somebody should be making an inline blade fuse, but there again, I'm not sure I've seen it. (Though it seems like an in-line fuse on a 4AWG wire must cost about $500 or so, huh?)
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Old 09-09-2011
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By all means, yes, bus bars and a clean installation.

The folks at Blue Seas tend to have a lot of diagrams on their web site. Take a look, sketch up something of your own, stick it on the wall for 48 hours and rethink it a couple of times. For instance, if you add larger batteries, or more equipment, can it adapt smoothly?

And don't forget, you want an insulating cover (even a sheet of plexi will do) over the positive cables/fuses/wires/bus, to make sure a stray bit of metal can't give you a bad day.
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If you already have a 150A MRBF on the positive terminal, then you don't need anything else. That's just about the right size for the alternator you're talking about, anyway, so just connect the alternator's positive output wire to the positive buss bar. I'm assuming a healthy size cable from the MRBF to the positive buss bar, like AWG 1/0 or better.

Depending on the distance from the alternator to the buss bar, I'd probably use larger cable, like 1 or 1/0. AWG4 or AWG2 are much too small for 100A loads in the engine space.

Bill
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Good tip on the sheathing... is there anything I should pay attention there regarding chafe? What do you think of this stuff: PVC Conduit, 105C

To be clear on the fusing issue... I throw a 150A fuse on the battery terminal, and I don't need any fuses between the buss bar and any of the following: Xantrex battery charger, Alternator, solar power, 1/2/both/off switch ?

It seems I read somewhere that all ungrounded power cables had to be fused.. but just the one fuse on the battery covers all of it?

(I understand that we are talking about fusing the wiring here.. most electronics have some form of internal protection of their own)

If I'm reading that right, you guys just saved me around $150 in fuses and mounts...
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Originally Posted by CapTim View Post




So what I would end up with is a large bus bar right next to the battery, and every post on that bus bar would have a Terminal Fuse of some size (the actual rating of the fuse can be changed easily and at no extra cost). Coming off that bus bar would be:
-All charging systems, each on their own post and fused appropriately
-A 1/2/both/off switch, which would then lead to the DC panels normally
-The bilge pump(s) (located here so that they are always on, but fused so they can be disconnected)

If all of that makes sense, would it also make sense to mount a bus bar for the negative stuff? It wouldn't be fused individually, of course, and would be mounted ahead of the shunt for the battery monitor. This bus bar could then take all the negative leads and connect to the house bank neg terminal.

Seems like this would make for easier trouble shooting down the road?

And, after all that text, I apologize if I just re-invented the wheel and all this is standard already. The books I have (Ed Sherman's and Wing's) seem to gloss over the actual nuts and bolts of connecting everything to the house bank.

I do that all the time. Two Blue Seas 4 post buss bars one positive and one negative and a bunch of MRBF fuses.

Here's one and sorry for the low quality pic:


I also do it with ANL fuses too..
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Originally Posted by btrayfors View Post
If you already have a 150A MRBF on the positive terminal, then you don't need anything else. That's just about the right size for the alternator you're talking about, anyway, so just connect the alternator's positive output wire to the positive buss bar. I'm assuming a healthy size cable from the MRBF to the positive buss bar, like AWG 1/0 or better.

Depending on the distance from the alternator to the buss bar, I'd probably use larger cable, like 1 or 1/0. AWG4 or AWG2 are much too small for 100A loads in the engine space.

Bill

He'll need to keep in mind that if this bank can be paralleled or used via a 1/2/BOTH/OFF switch to start the engien that a 150A fuse might not be enough to handle the starter loads depending upon the engine. In most cases it should not trip but a 200 or 250 would be better if starting is potentially involved.. For bank fuses I fuse to the wire @ 100% of the ampacity rating. I have rarely needed the 150% rule but I generally use 1/0 as my smallest for battery cabling and often it is 2/0...
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To be clear on the fusing issue... I throw a 150A fuse on the battery terminal, and I don't need any fuses between the buss bar and any of the following: Xantrex battery charger, Alternator, solar power, 1/2/both/off switch ?
No, you need a fuse to protect the wire at it's max ampacity rating based on in-engine or out of engine spaces.. I suspect Bill was referring to the alternator wire which could handle 150A if sized right but not the bilge pump, battery charger etc. etc.

Quote:
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It seems I read somewhere that all ungrounded power cables had to be fused.. but just the one fuse on the battery covers all of it?
Yes they do when connected to a "source", and your house bank is a source. Even if your buss bar is protected by a 150A the 10GA wire for the charger would melt and could catch fire well before the 150A fuse blew, or the bilge pump etc.....

Quote:
Originally Posted by CapTim View Post
(I understand that we are talking about fusing the wiring here.. most electronics have some form of internal protection of their own)
Yes protecting the wire is what this is about not protecting the device.

Quote:
Originally Posted by CapTim View Post
If I'm reading that right, you guys just saved me around $150 in fuses and mounts...
If a devices wire CAN be protected by a 150A fuse and the wire is sized for that ampacity then you don't need redundancy. If the wire is too small to be protected by a 150A fuse then you do need additional fuses.

I've seen some pretty scary stuff due to lack of fusing so your one the RIGHT path and thinking correctly!!
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Whatcha got against spaghetti?

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