I am trying to avoid stacking too many lugs on one battery terminal. I am looking for assurance that what I am about to do is the right way to do it. Battery bank consist of 5 Lifelines GPL-31T. With the batteries hooked in parallel and the house bank feed fused with 300 amp Class T fuse. Starter bank has its own lead and 300 amp Class T fuse. Both run to the 1-2-all switch. I will be running 140 amp alternator to house bank and solar controller output to house bank as well. Problem is I don't have enough existing 2/0 cable from house feed to run to a new fused bus bar to avoid stacking more than two lugs on a battery terminal. My thinking is to take house feed from positive side of battery and connect to bus bar. Then run new 2/0 cable from positive battery terminal through a 225 or 300 amp fuse either ANL or a terminal fuse block from Blue Seas to bus bar. The terminal fuse block kinda defeats the purpose because now I am stacking more than two lugs on a terminal. So would this be the correct way to do this? Second question is do I go with a 250 amp bus bar or do I need to go with the 600 mega bus bar. All wiring meets ampacity ratings and voltage drop is below 1% drop except alt. run which will be close to 1.5%. I realize that this diagram is very basic. I just want to help clarify my intentions.
Too many lugs
- Thread starter nautikaljeeper
- Start date
im sure im not answering all your questions, but in the proposed diagram, all the charge sources should go directly to the battery, and NOT into the system wiring.
this will insure all circuits are protected from spikes if the battery fuse blows, or if there is a failure of the regulators...
reading further prompts questions of my own... the house bank, I know you have lots of power in the system, but why such heavy wiring and such large fuses? how much power do your components draw from the house bank?... somehow, either I dont understand your need for sudden surges of power, or you have extremely oversized your proposed wiring plan.
this will insure all circuits are protected from spikes if the battery fuse blows, or if there is a failure of the regulators...
reading further prompts questions of my own... the house bank, I know you have lots of power in the system, but why such heavy wiring and such large fuses? how much power do your components draw from the house bank?... somehow, either I dont understand your need for sudden surges of power, or you have extremely oversized your proposed wiring plan.
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As far as fuses go I am just going with the Class T fuses that came with the boat. My understanding is fuse for wire
As far as fuses go the 300 amp class T is what came with the boat. My understanding is you fuse for the wire. 2/0 wire supports that. The Alt. fuse at 225 amp is 150% of possible output. What you say makes sense about charge sources should go directly to battery and that is my problem with connecting too many lugs to the positive battery post. I am thinking somewhere I need to include bus bars in the wiring to solve this problem. That is my purpose of the post.
Take a look at Reply #1 here: http://c34.org/bbs/index.php/topic,6604.0.html
It shows where the bus bars should go.
Good luck, you're on the right track.
You're right, of course, but it seems that you have sized the wire for the fuse, instead of the fuse for the wire. Size the wire for the load and the distance, and THEN size the fuse for the correct wire size. The fuse "supports" (i.e., protects) the wire; the wire isn't sized for the fuse that may have been there. I agree with the earlier post that said the wire seems quite large for the "traditional" loads most of use have on boats this size.
Thank you Stu. The diagrams is just what I was looking for. As far as the Class T 300 amp fuses go I agree that they are large. But the ampacity rating of a 2/0 wire is 330 amps. So educate me as to why that is over rated.
I really don't think any loads will come close to that. The boat is equipped with a windlass and cabin top powered winch. They could be larger draws but they are not used as the same time. Again thank you for the referral to the diagrams. I will rethink and repost for more evaluation. I welcome any suggestions.
I really don't think any loads will come close to that. The boat is equipped with a windlass and cabin top powered winch. They could be larger draws but they are not used as the same time. Again thank you for the referral to the diagrams. I will rethink and repost for more evaluation. I welcome any suggestions.
you should figure out your max load and size the wire accordingly.... with what you have planned, you could short circuit the entire system without coming close to blowing the main fuse..... so there really is no protection for it.
even with the max load that you could ever possibly achieve from the components on the boat, its highly unlikely that you will ever have all the components drawing power at the same time, so the actual load will still be below the theoretical max load....
it may be reasonable to upsize the wire a bit for future additions to the system, but a properly sized system will allow for this and still have some protection in the event of a system short circuit...
Referring to the class T 300 amp fuses you are saying I should downsize? As far as the other wiring to the solar, Alt, and ACR the diagrams Stu referred me to will be of great help.
im suggesting you should to assess your needs and size accordingly..... as I have said earlier, too big of wiring and too big of fuses protect nothing but themselves, and by the time you have a 200amp short circuit, you could easily have a fire started that a blown fuse wont put out.
I understand your point and thank you for the responses. I guess just because a boat comes from the factory wired the way it is may not be always right. Just a point to add is that there is step down circuit breakers to the DC panel, windlass and power winch. But your point is well taken.
I don't see a problem with 2/0 wire on any circuit that includes a windlass, electric cabin top winch, or possible engine starting from the house bank. Too many boats are wired with inadequate sized wires for these loads. Remember the wire size relates both to expected maximum load and voltage drop.
2/0 wire is what I use most often for battery cabling, but I have used larger on occasion.
While 2/0 has an ampacity of 330 it is reduced to 281 in engine spaces. 250 amp fuses could be a better choice. Class T fuses are the best but ANL or MRBF are commonly used as well.
The bonus of using large wire is faster engine starting and longer life of motors such as windlasses and electric winches.
Not sure how representative your diagram is but the fuses should be as close to the battery as possible.
2/0 wire is what I use most often for battery cabling, but I have used larger on occasion.
While 2/0 has an ampacity of 330 it is reduced to 281 in engine spaces. 250 amp fuses could be a better choice. Class T fuses are the best but ANL or MRBF are commonly used as well.
The bonus of using large wire is faster engine starting and longer life of motors such as windlasses and electric winches.
Not sure how representative your diagram is but the fuses should be as close to the battery as possible.
nk, I may have simply misread your first post and incorrectly thought you had the fuse before the wire (like the cart before the horse). If your LOAD requires 2/0 wire, then if that's the right fuse for it based on the tables, you're just fine.
I'd be interested in the load that you have that would require this size wire, though. Just professional interest, not saying it's wrong.
Either bank can be used for engine starting. 2/0 is a good choice for that.
Not to mention voltage drop over whatever distance the wire is run.
Busbars are a very good way to neaten up battery terminals. The first fuse off the battery should be the main bank protection then into an always-on distribution busbar for alternator charger etc... This meets the minimum safety standards. The alt feed can use an MRBF mounted directly to the busbar as can a charger or solar etc.. Your position of the solar ANL is incorrect, it should be at the busbar. These fuses are to protect the wiring from the battery.... Also any time you step down in wire size a new fuse is necessary ideally sized to not exceed the ampacity of the wire..
Your wiring is absolutely not oversized and is standard Hunter, Catalina, Beneteau, Jenneau, Sabre etc., factory wiring by today's standards. Builders do this because they need to meet bank over current protection requirements as well as accommodate an owner for inverters, electric winches, engine starting and thrusters. It is just good practice and if you add or have a 2kW + inverter you'll be very happy the builder did not cut corners like they used to. The 2kW Magnum inverter I installed 4 weeks ago requires a bare minimum (the smallest allowable) of 2/0 wire and a 300A Class T fuse. Heck just to start engines I like to see a bare minimum of 250A but much more preferably 300A. You can't really do this with 2GA or 4GA wire and meet the safety standards. Hunter did not oversize your wiring they did the right thing.
As for the position of the alt fuse it is really pretty irrelevant, if the fuses are sized correctly. Seeing as you've already removed the number 1 voltage transient reason, and that is controlling alt source selection via a battery switch, you're in much better hands by feeding it direct to a bank.
Even with the slew of blown diodes in alts I repair each year, all of which threw a huge spike into the DC system because the alt was directly connected to the "C" post of the switch, the same place the DC loads are wired to, I see very, very few electronics failures even on boats that literally blew the diodes out of the alt by disconnecting or open circuiting the bank from the alt all while leaving it directly connected to the DC loads.. If you are overly concerned about that simply mount an alt MRBF to the battery side of the Class T. I would not lose sleep over it....
Battery main over-current protection is only there to protect the battery wiring, nothing more...
If the boat is wired correctly then this is not possible (unless the fire was started by high resistance and in this case no fuse will protect against that). The 300A fuse is only there to protect the battery wiring from the battery bank, nothing more. Each time the wire size steps down so should the over-current protection ideally within 7" of the step down or transition from larger wire to smaller wire... If it does not, the boat is simply not wired correctly or safely.
One of the biggest violations of this is at the "C" post of a battery switch where 2/0 wire protected by a 300A fuse feeds the "C" post when the switch is made. The DC panel may then be fed from the "C" post by a 4GA or 6GA wire and builders, boat yards, DIY's and installers very, very often omit a fuse or breaker to protect the 4GA or 6GA wire within 7" of the battery switch. Most late model Hunters I have been on have step down protection for panel feeders and they are usually wired in a fairly okay manner..
"Your position of the solar ANL is incorrect, it should be at the busbar. These fuses are to protect the wiring from the battery.... Also any time you step down in wire size a new fuse is necessary ideally sized to not exceed the ampacity of the wire.."
Thank you Maine Sail I see that now. I have another question and I thought I have read from your past postings that some sort of circuit protection should be used between solar panels and controller. I am considering a circuit breaker but would like to know what size would be best. I thought you have said to size just under ampacity of wire run for the least possible resistance. 10 ga wire and (2) 240 watt panels with VOC being 52.4 and the Isc at 5.85 amps wired to a Midnite Kid MPPT controller. If I got it right that would lend me to use a 50 amp breaker. I won't be getting that kind of power out and chances are the breaker wouldn't even be of use for some kind of short. My choice for the breaker instead of a fuse would be for easy power disconnect.
There is no need, requirement nor desire to install a fuse or breaker between panels and controller on a boat. This is a current limited device and there is really little chance the PV could trip the controller side wiring fuse if that fuse & wire was properly sized. In this application it offers no real safety advantage just more points to corrode, adds more voltage drop and additional adds expense. With properly sized wire for minimal voltage drop you can literally short your PV and the wire won't catch on fire.
There is a need to have a fuse within 7" of the battery (thousands of amps of short circuit current waiting inside the battery) for the wires to the controller.
If you want to shut down the controller check with Midnite on the best course of action. Some want input cut first, some want output cut first and some require a double pole switch to break both simultaneously. I have had two different answers from Midnite over the years on this so will be curious as to what they tell you..