Buss bar and fuse calculations

[Manateeman]

Finally have time to redo the primary dc house system and would appreciate comments. It’s a 24 volt stand alone system. Starting 12 volt system is separate. Main bank is four, 6 volt new Rolls FLA in series for 700 AH at 24 volts.
The cold cranking amps are 1742 and CCA marine at 2177. Amp interrupt capacity 5,000. Correct?
Inverter is Outback FX 2524 mt. 2500 W typical DC input 104 amps, NEC 130.
The charger side needs repair so it’s run only as an inverter.
Current T class fuse JLLN 200 amps.
Current Battery switch Blue Sea 350 amp.
Two Charles 50 amp chargers.
Solar system. Six 285 W panels to Schneider Controller. 60 amp breaker in, 80 amp breaker out. Solar fuses on DIN rail. Midnight lightning protector.
Loads.
Maxwell windlass on 80 amp 185 breaker.
Two 24 volt panels for everything else.
Starting at the battery bank is where I need advice. Battery bank to
Battery switch number 1... Blue Sea... but 350 or 600?
Next, T fuse number 1 ...recommendations?
Next Blue Sea 600 amp buss bar with 4 posts and I’m thinking :
Post 1, to windlass. I need to add an ANL fuse here ( it’s 8 feet to current 80 amp breaker) Size?
Post 2, feeds in from cable with a battery switch and a T fuse fuse..directly from the main bank.
Post 2, feeds out to inverter. I’d like to add a switch. 350 amp? before existing T fuse. So post 2 is supplied from the battery bank and the only load is the inverter directly across the buss bar.
Post 3, a short jumper bar to a BEP 500 amp, 3 post bar. This is where I’ll connect the solar and the two battery chargers. I should put a breaker on each of the chargers...correct?
Post 4 is the feed to the two 24 volt panels. The everything else post. I’m thinking breakers not ANL.
I’m trying to keep it simple so that only one post on the main bar has two lugs.
I apologize I don’t know how to post a drawing.
The manatees broke all my crayons when the ran out of beer.
Sincere thanks to all contributors in advance.
Happy trails to you
Mark and his uncontrollable when drinking manatees

[tkeithlu]

Be careful, manateeman. They are not to be trusted. One day when you are least expecting it one will sit on you.

I've got a monster relay that lets you series or parallel two batteries (or banks) with a low amperage toggle switch. They were made for starting trucks; 24v will really spin a 12v starter motor. You are welcome to it if it will help you with your hybrid 12/24v system.

[Bycrick]

24/12 dual system is what I should have done. Good on ya'.

Keep the engine system 12 v. If you don’t have dual alternators, charge the starter battery with a DC-DC charger. Make sure there’s a way to shut the charger off so that it doesn’t try to charge the poor starter battery all the time.

Outback used to do board exchanges. They send you a new one, you install it, return the old one in the same box. Way cheaper than sending them back. A simple job, and the instructions were every bit as good as the old Heathkit instructions, which were legendary for allowing people with no electronics knowledge at all to build their own stuff.

Class-T fuses are overkill with 20k AIC. But they look nice and aren’t that much more expensive for main battery and inverter fuses. MRBF fuses have 10k AIC for smaller circuits. ANL fuses might be easier to change, but only if you get the fuse blocks that have separate studs for the wires and the fuse.

The 350 amp Blue Sea switch only has that rating with 4/0 cable. If in doubt, spend a little extra for the 600 amp switch.

If you wire the solar panels in series, make sure the fuses or circuit breakers on the input side of the controller have high enough voltage rating.

185 amps fuse sounds high for a 24 volt windlass unless it’s huge.

Starter battery. My Yanmar 4JH2 has run for years with a 200 amp MRBF fuse at the battery. The 350a switch ought to be fine, unless you’ve got a big motor. Class-T fuse not needed because the starter battery is unlikely to put more than 3000 amps into a short circuit.

Big bus bars. As you pointed out, the Blue Sea ones are very conservatively rated.

Most chargers require fuses on the battery wires. MRBF are fine.

Tell the manatees hello.

[noelex 77]

With the equipment you have on 24v, the BlueSea e series battery switches (350A) should be fine. For the 12v engine start it will depend on the engine.

Unfortunately, the larger HD battery switches are only available as a single pole version. This means two are required with the dual pole switching that is normally fitted on an aluminium boat. The e series comes in a dual pole version and so is much more suitable for an aluminium boat.

[Manateeman]

My 24 volt system is not connected in any way to any engine on the boat. That’s all 12 volt. I’m trying to have as few lugs as possible but I need some way to disconnect the battery bank...for example to replace the first T class fuse.
Are you recommending the negatives be shut off a the same time ?
Sorry. I’m not being argumentative, I just don’t see what this has to do with an aluminum hull. We have no electrical leak that I can find anywhere.
We slathered the hull bottom in epoxy and we never sit on a dock. We’ve never plugged the boat into shore power. The bilge pumps are not sitting in water.
Maybe I’m mis reading your post.
Mark and his confused manatees.

[Bycrick]

WRT battery switch sizing. Why try to save $30 by using smaller switches?

Lots of aluminum boats switch both sides of the battery circuits. The idea is to eliminate any possible current flow. Lots of European glassboats do also. Some people think it helps prevent lightning damage.

Isolation of the battery minus from the boat requires constant care. Each piece of equipment has to be checked to make sure that it’s truly isolated. VHF antenas, SSB radios and tuners, car stereo systems often will end up with -12 connected to the case. Just because something has a minus wire doesn’t mean it’s not connected to the case.

Making sure the engine block and circuits aren’t somehow connected to both the hull and the -12v is a job. It usually means modifying the motor wiring unless the motor has a factory modification to isolate everything: isolated starter motor and alternator, ungrounded sensors and fuel pump, run/stop solenoids, etc. shift and throttle cables.

You need a way to charge the 12 volt starter battery. A second alternator works, or separate solar panels/controller, or an ISOLATED DC-DC charger.

You might not have problems right now with things connected to the hull, but it will happen eventually unless you watch it all the time. Case in point, an Amel with a very carefully isolated Volvo engine. Someone replaced all the instruments at the helm. So he needed to fill all the old holes. So they made a big aluminum panel with new holes. Mounted the shifter to the panel. Then added an after market meter with a grounded metal case.

[sailormed]

Originally Posted by tkeithlu

Be careful, manateeman. They are not to be trusted. One day when you are least expecting it one will sit on you.

I've got a monster relay that lets you series or parallel two batteries (or banks) with a low amperage toggle switch. They were made for starting trucks; 24v will really spin a 12v starter motor. You are welcome to it if it will help you with your hybrid 12/24v system.

I think we have the same setup. I use the same truck series/parallel switch to get 24 volt for the bow thruster coupled with an alarm so I know not to forget to switch it off before overheating.

[noelex 77]

Originally Posted by Manateeman

My 24 volt system is not connected in any way to any engine on the boat. That’s all 12 volt.

This 12v system will need a battery switch. As it needs to carry the starting current if it is a large diesel (as it may be on a 60 foot boat) on 12v, it could require the larger HD 600A battery switch or switches (two will be required if you want to isolate both poles). I would think an e series switch (350A) is probably adequate, but it is worth contacting Bluesea for their recommendation.

Originally Posted by Manateeman

Are you recommending the negatives be shut off a the same time ?
Sorry. I’m not being argumentative, I just don’t see what this has to do with an aluminum hull.

Yes, normally for an aluminium boat both the positive and negative sides are switched. This requires both dual pole battery switches as well as installing dual pole devices for all the secondary protection systems (usually circuit breakers). This is not essential, but virtually all modern aluminium boats such as those produced by Alubat (Ovni) Garcia, Allures, Boreal etc etc are wired in this fashion. Some home made and older aluminium boats, especially racing boats skip this important protection, and try to ensure a single grounding point to the hull. The risk of stray current corrosion is significantly higher.

This is not needed on a fibreglass or wood boat, although it does have some small advantages. Some commercial vessels require dual pole battery switches (not usually secondary devices) as part of their certification.

[Manateeman]

Very interesting. I think I’ll take another look at my 12 volt system. I don’t have SSB but I didn’t think about the VHF.
I’ve done about everything I can with the 12 volt system and the two motors, main and gen set but I’ll take another look.
Remote battery switches would be nice when we go ashore.
Interesting comment about lightning. We might have had a strike near us that jumped N to Ground inside the lead in lugs on the AC side of the inverter.
Just don’t have time to fix it right now as I’m trying to finish building the spars.
Anyway, sincere appreciation for the advice from all.
Happy trails to you
Mark and his “this boats a Tesla coil” manatees..yikes.

[Q Xopa]

Originally Posted by Manateeman

Finally have time to redo the primary dc house system and would appreciate comments. It’s a 24 volt stand alone system. Starting 12 volt system is separate. Main bank is four, 6 volt new Rolls FLA in series for 700 AH at 24 volts.
The cold cranking amps are 1742 and CCA marine at 2177. Amp interrupt capacity 5,000. Correct?
Inverter is Outback FX 2524 mt. 2500 W typical DC input 104 amps, NEC 130.
The charger side needs repair so it’s run only as an inverter.
Current T class fuse JLLN 200 amps.
Current Battery switch Blue Sea 350 amp.
Two Charles 50 amp chargers.
Solar system. Six 285 W panels to Schneider Controller. 60 amp breaker in, 80 amp breaker out. Solar fuses on DIN rail. Midnight lightning protector.
Loads.
Maxwell windlass on 80 amp 185 breaker.
Two 24 volt panels for everything else.
Starting at the battery bank is where I need advice. Battery bank to
Battery switch number 1... Blue Sea... but 350 or 600?
Next, T fuse number 1 ...recommendations?
Next Blue Sea 600 amp buss bar with 4 posts and I’m thinking :
Post 1, to windlass. I need to add an ANL fuse here ( it’s 8 feet to current 80 amp breaker) Size?
Post 2, feeds in from cable with a battery switch and a T fuse fuse..directly from the main bank.
Post 2, feeds out to inverter. I’d like to add a switch. 350 amp? before existing T fuse. So post 2 is supplied from the battery bank and the only load is the inverter directly across the buss bar.
Post 3, a short jumper bar to a BEP 500 amp, 3 post bar. This is where I’ll connect the solar and the two battery chargers. I should put a breaker on each of the chargers...correct?
Post 4 is the feed to the two 24 volt panels. The everything else post. I’m thinking breakers not ANL.
I’m trying to keep it simple so that only one post on the main bar has two lugs.
I apologize I don’t know how to post a drawing.
The manatees broke all my crayons when the ran out of beer.
Sincere thanks to all contributors in advance.
Happy trails to you
Mark and his uncontrollable when drinking manatees

You didnt mention what size/ power your Inverter, Windlass etc are. I got my Fuse sizes recomendations direct from the manufactures manuals.

So in my case for my 24v 3000kva inverter Victron lists a 300A ANL fuse.

By the way, it's often not done but Inverters, according to Victron and AYBC, need a Service disconnect Switch.

For my 24v 1200w Nilsson Windlass the fuse size is 80A.

Dual pole isolation switches I agree its good to have even on a glass boat, as mine is, on for example the Windlass power. Anchor chain can corrode quickly without isolating the Neg.

[Manateeman]

I took the windlass and inverter fuse requirements from the factory...seems ok.
I will start a separate thread for my 12 volt stand alone system as it has its own solar and charger and panels.
I’ve been around the boat with my meter just looking for trouble. Yesterday I went scuba to clean the prop and check the zincs. Six in the hull and one on the shaft. All OK . However I have an something odd going on with the two Charles 50 amp battery chargers. Called the factory and they were not sure buts its winter and I don’t want to send the unit out till summer solar.
I turn on the generator. If I flip on both breakers (220 ) charger #2 pops out after a few minutes. Alone, it works fine. So does charger #1. Both the same size, both by the same manafacturer.
If I run charger #1 for 10 minutes, I can turn on charger #2 and they will work perfectly together. I checked all the ac and dc wire and tried another breaker.
New house battery bank never under 60%.
Some sort of “ripple”: I’m not sure I understand what ripple exactly is.
Ran a heat gun over everything. The two chargers have different length ac and dc cables. I’m going to redo all the dc . Anyone ever seen this gremlin before?
I hope when he sees all my new buss bars, fuses switches and my monster crimped...he will jump ship.
Happy trails to you
Mark and his “we need a neon bar light” roudy manatee gang.

[Bycrick]

"Ripple?" AC is supposed to be a sine wave. When you rectify it to convert to DC, you end up with two half-sine waves. So the voltage varies from zero to the peak voltage at twice the frequency of the AC. If you then put at battery or a capacitor across the output, since either of them stores energy, the output voltage doesn’t go down to zero between the half-cycles. If you look at the output with a oscilloscope, you’ll see a DC voltage, with some AC variation on top of it. That superimposed AC is the ripple. Ideally, you’d want pure DC to charge the battery, but there’s almost always some ripple out of charging systems. There’s all matter of opinions on "how much is too much." I don’t think that’s your problem.

My first test would be to try the chargers/breakers on SHORE power, not the Genset. Without going into a lot of details, just because a Genset puts out AC doesn’t mean it’s identical to what you get from the power grid.

I once had an old Heart inverter. On real shore power, it would put out 90-100 amps. On my Genset, it wouldn’t even turn on properly. If I ran a 1000-watt hairdryer at the same time, it would output about 65 amps. Why? Because it had a big 60Hz transformer which was a very inductive load which the Genset had trouble with. As to the AC breakers tripping, Google the definition of "power factor." Highly inductive loads have a lower power factor and thus draw more input current for a given output current.

My bet is the combination of the Genset and the chargers.