Complete new electrical install.

[burgundyben]

Since the boat sank a couple of years before I bought her, I feel the need to do a complete rewire.

She is a twin engine semi-displacement motorboat 31ft.

Here is my plan.

12v starters and alternators. Starter motor relays
One battery for engines - Numax CXV24MF with 780 CCA (manual says it needs 695 CCA) - to Minimise cable lengths this could be mounted centrally
Batteries 3 in parallel for the domestics - Humax CXV24MF 80 amp hour
Port engine alternator charges the engine battery.
Starboard engine alternator charges the 3 * domestic batteries.
Solar panels on the wheelhouse roof with MPPT controller outputting to the domestic bank only, wired so working while isolators are off. Sized to be able to run fridge all day in summer without losing charge.
Anchor windlass 1000W 12V
2 isolator switches one for engine battery, one for domestics, both mounted in wheelhouse on bulkhead by the door (Durrite 0-605-50)
Third isolator under the floor out of reach which connects domestic bank to starting battery if needed. (Durrite 0-605-50)
Dometic CRX50 fridge - 5 amp draw, 15amp fuse for inrush, need to size solar panels to run fridge
Inverter - 2000watt?
5kw diesel Chinese heater outlets in cabin, heads and wheelhouse.
Electric bog.
Bilge pumps? 3 auto, aft, mid, fwd. Connected so always on regardless of isolator switches
Horn
Flood light
Freshwater pump
USB Charging
Wipers
Washer jets

Dash
Tachos
Fuel tank gauges
Engine Temp
Engine Oil Pressure
Ignition switches
Charging warning light - route to the alternator exciter
Exhaust alarms - Aqualarm - already onboard
Engine box fire alarms - Aqualarm already on board


Nav/Comms
VHD DSC - Standard Horizon
AIS - RTE?
GPS - SOG, Waypoints, MOB, position
Log/Echo - paddlewheel - NASA Clipper Duet


Lights
Cabin
Heads
Wheelhouse
Red night light in wheel house
Cockpit
Underwater
Nav lights - reg/green/steaming, stern anchor
Flood light for cockpit
Underwater LED at transom.

Comments?

 

[vas]

looks OK Ben,

why three small service batteries in parallel? why not less (well two, or even one!)?
also why washer jets? mine has the jets on the freshwater circuit and has a nice cock to turn on/off regulate water coming out through them, all manual, minus two cables
pretty sure with led lights and all, 150Ah would be plenty to run your fridge 24/7 together with 200W solar (or thereabouts) assuming there will be some light and sun occasionally.
Ah, re electrics, I'd get a Victron BMV and MPPT, the monitor has a relay you can program to turn something off (say the fridge) if SOC is low (all configurable)

 

[PaulRainbow]

A lot to look through Ben, a couple of immediate thoughts:

The third switch, connect it to the load side of the other isolators, that way, you can isolate a faulty battery and use the remaining bank for everything.

Alternators, connect each alternator to a Victron Argofet, then connect the two outputs of each Argofet to each battery banks. The engine battery will quickly re-charge, then both alternators will charge the domestics.

 

[john0740]

OP's plan is to connect multiple domestic batteries in parallel.
I suggest consideration of having switches on each domestic battery to allow for isolation in the event of a faulty battery if needed.

 

[William_H]

I would suggest if at all feasible to consider going 24v system. This will give far better starting and anchor winch operation. Also can't imagine it not better to parallel the outputs of the alternators via a balancing regulator to share the charge load. Very common on twin engined aircraft not sure what is available for marine use. Gives full functionality on one engine or one alternator. ol'will

 

[PaulRainbow]

I would suggest if at all feasible to consider going 24v system. This will give far better starting and anchor winch operation.

That means an additional engine battery, additional domestic battery, new starter motors, new alternators, new windlass and new equipment to reduce 24v to 12v for domestic equipment. Seems like a lot of trouble and expense for little or no benefit.

Also can't imagine it not better to parallel the outputs of the alternators via a balancing regulator to share the charge load. Very common on twin engined aircraft not sure what is available for marine use. Gives full functionality on one engine or one alternator. ol'will

See post #3 ?

 

[TernVI]

I think on a motorboat with a siginificant domestic load like a fridge, I would consider some sort of smart charging of the house batteries?
I'd want to make the best of charging from a short run of the engines.

Starting big engines, wiring resistance is your enemy, might be better served by not sharing the start battery? Depends on the physical layout.
If there's a good route for the cables, then a single battery does make sense.

I have some sympathy with people who would say a switch labelled 'battery isolator' should isolate the battery.
This could be important if a cell fails at end of battery life.

The diagram is incomplete without the solar of course.

It's an excercise for the reader to work out if the fuses can every actually blow or just give a false sense of compliance or something?

 

[burgundyben]

why three small service batteries in parallel? why not less (well two, or even one!)?

also why washer jets? mine has the jets on the freshwater circuit and has a nice cock to turn on/off regulate water coming out through them, all manual

Hi Vas

Because I have 4 brand new ones. Long story. Starting from scratch I might have bought differently. But it is what it is. Plus the smaller ones are easier to package.

Washer jets - yes, exactly, I think a ball valve in the wheelhouse and plumbing running off the fresh water pump.

A lot to look through Ben, a couple of immediate thoughts:

The third switch, connect it to the load side of the other isolators, that way, you can isolate a faulty battery and use the remaining bank for everything.

Alternators, connect each alternator to a Victron Argofet, then connect the two outputs of each Argofet to each battery banks. The engine battery will quickly re-charge, then both alternators will charge the domestics.

Thanks Paul. Brill diagram, much clearer than my fag packet sketch!

Good point about the isolator bridge, I hadn't thought of that.

I was sort of in 2 minds about the Argofet idea, but you've convinced me. The boat will have 2 brand new alternators, but they are likely to be Chinese copies, so the charging redundancy given by the Argofets will be a useful back up.

I will there was a bellhousing for my engines with 2 starter positions, that way I could have a wind up kinetic starter motor so I could have a complete black start capability!

OP's plan is to connect multiple domestic batteries in parallel.
I suggest consideration of having switches on each domestic battery to allow for isolation in the event of a faulty battery if needed.

Nice idea, but also added failure points. I'll mull that over.

 

[PaulRainbow]

Washer jets - yes, exactly, I think a ball valve in the wheelhouse and plumbing running off the fresh water pump.

Or, plumb this into the freshwater system and fit a momentary switch at the helm: Windscreen Washer Pressure Solenoid 12V

Thanks Paul. Brill diagram, much clearer than my fag packet sketch!

Good point about the isolator bridge, I hadn't thought of that.

I was sort of in 2 minds about the Argofet idea, but you've convinced me. The boat will have 2 brand new alternators, but they are likely to be Chinese copies, so the charging redundancy given by the Argofets will be a useful back up.

The redundancy is nice, you could have managed by using the emergency switch, but the Argofets are a nicer solution as they don't require having the batteries in parallel. But, more importantly, after a very short time, the surplus output from what would have been the engine battery alternator will be going to the domestic bank.

 

[Stemar]

It's an excercise for the reader to work out if the fuses can every actually blow or just give a false sense of compliance or something?

If the fuses have been sized correctly, they'll blow before the wiring catches fire but if a fuse that handles starting loads does blow, something pretty spectacular will have gone wrong! One fuse that I'd consider adding to PR's diagram would go in the supply to the domestics, as near as possible to the isolator but it probably isn't really necessary if the run's short and well protected.

 

[PaulRainbow]

The diagram is incomplete without the solar of course.

Are you referring to my diagram ?

If so, of course the solar is missing, so is a lot of other equipment. It's simply an illustration of the alternator charging, using Argofets, that i described in the post that the schematic accompanied.

It's an excercise for the reader to work out if the fuses can every actually blow or just give a false sense of compliance or something?

It's nothing of the sort. It's an illustration of where the (optional) fuses would be placed. Correctly spec'd fuses would blow. There is no compliance issue, the OP has nothing to comply with.

 

[PaulRainbow]

If the fuses have been sized correctly, they'll blow before the wiring catches fire but if a fuse that handles starting loads does blow, something pretty spectacular will have gone wrong! One fuse that I'd consider adding to PR's diagram would go in the supply to the domestics, as near as possible to the isolator but it probably isn't really necessary if the run's short and well protected.

Spot on, on all counts.

I took the closest diagram i had to Bens proposed installation and modified it to suit, to simply illustrate the Argofet installation. The engine fuses and the fuse to the distribution board are optional and variable, depending on the precise installation. The installation the original schematic was intended for was a 60ft twin engined motor cruiser. The battery cables took routes that made the fitting of battery fuses important. The cable to the electrical distribution centre was the same size as the battery cables, so it was protected by the battery fuse. From the distribution centre, individual circuits were fused accordingly.

 

[JumbleDuck]

Underwater LED at transom.

Comments?

A bit "white stiletto", old chap.

 

[PaulRainbow]

More thoughts:

"Dometic CRX50 fridge - 5 amp draw, 15amp fuse for inrush, need to size solar panels to run fridge"

Fit the biggest fridge you have sensible room for, a bigger fridge doesn't cost that much more or use much more power. Don't size the panels for the fridge, fit the biggest you have room for (within reason).

"Inverter - 2000watt? "

Sounds about right.

 

[burgundyben]

I think I can get about 400w of solar panels on the wheelhouse roof.

Gas locker is falling apart and dreadfully placed, I'm struggling to find a decent place for a new gas locker...so...bin the gas...

Get a girt big inverter and switch to a 2 ring induction hob. Perhaps even a microwave tucker fu**er oven.

Maybe.

 

[superheat6k]

I have the OE wiring diagram for the Turbo 36 plus those following mods, plus those for my Corvette - booth twin engine mobo's. Happy to send them to you to see if they give you inspiration.

I have 1 x 95a stbd engine + windlass and 2 x 95a port engine + domestics.

I am interested in the Victron Argofet's - where is best place to buy these ?

I use Electric Design app on my Mac for wiring diagrams.

 

[PaulRainbow]

I have the OE wiring diagram for the Turbo 36 plus those following mods, plus those for my Corvette - booth twin engine mobo's. Happy to send them to you to see if they give you inspiration.

I have 1 x 95a stbd engine + windlass and 2 x 95a port engine + domestics.

I am interested in the Victron Argofet's - where is best place to buy these ?

I use Electric Design app on my Mac for wiring diagrams.

Battery Megastore are usually good for Victron prices.

 

[Scarron]

Perfect timing, exactly what I am looking for, I am currently wiring a similar twin engine 12v installation. Ben knows all about it as he has been my very able assistant! It's exactly the same use case but scaled up a bit on battery capacity and domestic draws.

My plan is to have
Engine start: 1x Numax CVX 35MF 120A 1100MCA to start both engines
Domestics: 4x Numax CVX 35MF 120A 1100MCA to give 480ah of house capacity, or maybe 6 to give 720ah

Inverter/charger: Victron Multiplus 12/3000/120-16, this should have enough grunt to run all electric cooking with microwave + induction hob [not both at once] and re-charge rapidly when connected to shore power.

I have two questions, firstly:-my understanding is that the two Argofets will allow both alternators to charge both batteries simultaneously. The charge rates are I assume controlled by the standard alternator regulators and therefore produce a slow-ish charge.

I like the idea of the Sterling battery to alternator chargers ability to properly 4 stage rapid charge. Is there a means to add something similar to the Argofet charge circuits as drawn to increase the charging capacity of the engine alternators or is the Sterling B to A the only option? I have AC5 RS 12v alternators which are machine sensed [I think?]

Secondly:- With regard to battery fuses, am I right that they should be sized to the inrush current of the starter motors? I have CAV CA45 G12 55M which appear to be rated at 3.6Kw so 3600/12 = 300 amps so would say 350A be sufficient or would the stall/inrush current be much higher?

 

[burgundyben]

Secondly:- With regard to battery fuses, am I right that they should be sized to the inrush current of the starter motors? I have CAV CA45 G12 55M which appear to be rated at 3.6Kw so 3600/12 = 300 amps so would say 350A be sufficient or would the stall/inrush current be much higher?

It depends on the time profile of the fuse, my understanding is that slow blow fuses are used in situations where there is in rush current.

The isolator switch I WhatsApp to you yesterday is only 250amps continuous and 2500ps for 5 secs.

Would be interesting to see the profile of the current flow when we get the beasts fired up.

 

[pvb]

I like the idea of the Sterling battery to alternator chargers ability to properly 4 stage rapid charge. Is there a means to add something similar to the Argofet charge circuits as drawn to increase the charging capacity of the engine alternators or is the Sterling B to A the only option? I have AC5 RS 12v alternators which are machine sensed [I think?]

If you fit a Sterling Alternator-to-Battery Charger, you wouldn't need ArgoFET isolators. The A-to-B has isolated outputs for the start and domestic batteries, and will accept input from multiple alternators.