Gunboat Electrical Refit- Adding Aircon, Generator & 2 Victron Multiplus 3kw

[osi48]

I am in the middle of a refit on our new to us 48' Gunboat, and need some electrical expertise. I have scoured the internet, but as usual everyone's installation is a little bit different. I am adding a generator and air conditioning to keep the old lady happy. There is no getting around it, I hate to add the weight but its a done deal. Happy Old Lady = More Cruising, plus she works remotely and says that she has to be comfortable on the boat while working when its hot out or she is going to retire. Not ready to give up that extra income yet

Here is the current set up:

Boat is wired for 12v & 120v

12v Batteries:
Each Battery has built in BMS, and a CAN network output to a Victron Battery Monitor and GX Color Control Screen

- 5ea Super B Nomia 12v 210ah House Batteries - 500a continuous discharge per battery - Wired in parallel with 4/0 to the main house switch then to the main bus and split off to different switches (2ea 12v winches, 1ea 12v windlass, 1ea 12v watermaker, 3ea 12v appliances- Fridge, Freezer, Pumps, 3ea 12v empiribus systems for lights and low voltage electronics, 1ea 12v Backup System for emergency equipment -GPS, Nav Lights, VHF, Radar, Autopilot etc... in case the empiribus system were to crash)

- 3ea Super B 12v 50a Thruster Batteries - 150a continuous discharge - Individually wired to each thruster (2 Bow, 1 Stern) with 2/0 to the switches (6' run) then 4/0 from the switch to the thruster (15-30' run depending on the thruster)

- 2ea Super B Mason 12v 25ah Starter Batteries - 260ah continuous discharge - Individually wired to each motor with 1/0

12v Power Sources:
10ea 12v 160w Ecosolar Panels
2ea 12v 120amp Alternators - one on each motor. Wiring is 1/0 from Alternators to Argo Fet Isolators

Solar Controllers
2ea Victron MPPT Solar Controllers - One for Port Solar Panels, One for Starboard Solar Panels. Wiring is 1/0 from MPPT to Isolator

Isolators:

Isolator #1 - Victron 200amp 3 output Argo Fet
Input Power - From the two MPPT Solar Controllers in 1/0 (2 inputs on 1 post - is that ok?)
Output #1 - to isolator #2 in 1/0
Output #2 - to isolator #3 in 1/0
Output #3 - Not Used

Isolator #2 - Victron 200amp 3 output Argo Fet
Input Power - from Isolator #1
Output Power #1 - Starboard Stern Thruster Battery in 1awg
Output Power #2 - Starboard Bow Thruster Battery in 1awg
Output Power #3 - Port Bow Thruster Battery in 1awg

Isolator #3 - Victron 200amp 3 Output Argo Fet
Input Power - from Isolator #1
Output Power #1 - Starboard starter battery in 1awg
Output Power #2 - Port starter battery in 1awg
Output Power #3 - To House Bus in 1/0

Isolator #4 - Victron 200amp 2 Output Argo Fet
Input Power - From Starboard Motor Alternator
Output Power #1 - to House Bus in 1/0
Output Power #2 - to Starboard starter battery in 1awg

Isolator #5 - Victron 200amp 2 Output Argo Fet
Input Power - From Port Motor Alternator
Output Power #1 - to House Bus in 1/0
Output Power #2 - to Port starter battery in 1awg

Parallel Switches -
Each Motor Has a Parallel Switch allowing it to start using the house battery bank in case the starter batteries were to die/loose charge

Inverters - Being Installed Now
2ea Victron Multiplus 3000w Inverters in Parallel

Generator - Ordered Waiting on Delivery
1ea Northern Lights 6kw 120v w/ Isolated Ground

Air Conditioners - 2ea - Ordering this week
Torn Between the Velair i16VSD and the Ocean Breeze 16.7k with Softstart

Velair-
Pros: 9amp draw @ 16k BTUs
Cons: Price, Availability, is a bigger unit dimensionally and would be a tighter squeeze, only a 471cfm blower fan, plus I am not 100% sold on the variable speed technology. I have had multiple issues with high efficiency variable speed heat pumps @ different properties. Replaced them all with standard 3 speed models.

Ocean Breeze -
Pros: Price, Availability, Slightly more BTU @16.7k, 560 CFM Fan, Made in the US (with the same parts everyone else is using), attractive pricing, fits my cabinet space well, no crazy logic board, should be easier to service and get parts if something breaks.
Cons: Higher amp draw - 11.6amps @ 16.7k BTUs (the 13.6 amp draw listed on there website includes the 2amp march seawater pump)

My gut tells me to go with the ocean breeze, but I am still hesitant to pull the trigger. Thoughts?

Additional Information

So we have already converted the boats AC from 220 @ 50hz to 120 @ 60hz using a single Victron Multiplus (Fortunately all the wire on the boat was 12 and 14ga ancor tinned copper wire, so it was really just changing outlets and breakers.) When we did this we replaced a single Victron Phoenix 12/1600w 220 @ 50hz with a single Victron Multiplus 12/3000w 120 @ 60hz unit.
When we did this we increased the wire size from 1/0 to 2/0 from the main bus to the inverter per the Victron dealers recommendation (6' run). The boat originally did not have shore power, so we added a 50amp @60hz input with 6/3 wiring to the Multiplus to charge the house bank when we are at the dock.

I am now adding a second Multiplus (same unit, serial range, and firmware) to help power the soon to come air-conditioning systems for 2-3 hour periods when we don't want to run the generator. I have come to find out that I probably should have wired the 1st Multiplus in 4/0, and the second also in 4/0 so I will probably redo the wiring on that later this week and run them straight off the batteries, skipping the main house bus.

First Major Question - Should I run the 4/0 run from the batteries to the inverters direct - skipping the main bus. Or from the Batteries to the Main Bus to the inverters? If from the batteries direct I will add an additional pair of 400amp fuses (one on each positive line) that then connect into a single blue sea systems 3000 switch which is rated for a 600a continuous discharge? Or into separate switches - one for each inverter?

I am not sure, but I would imagine the inverters may not like it if only one is turned on, so this eliminates the possibility of having one switch on and one switch off, which may confuse the multiplus once they are configured for parallel operation? What would be the best install here?

Second Major Question - Each battery has a 500amp continuous discharge, does this stack when batteries are run in parallel? Will the 500amp continuous discharge be my max bottle neck? It should be close to the maximum I could ever need if everything is running off the batteries @ the same time - which would be super rare, but you never know.
If the 500amp max draw is my bottle neck then 500a @ 12v or 50a @ 120. I probably need 27amps @ 120 for the aircon (Assuming I go with the ocean breeze units) and another 10-15amps or so for 120v outlets (Coffee Maker, Hair Dryer, or Power Tools on a limited basis) so 42 amps @ 120 = 420amps @ 12v (not including any power loss when converting power) which would only leave me 80amps @ 12v for the fidge/freezer and low voltage electric. I cant imagine we will be using the aircon if we are sailing, so I am going to exclude the windlass and electric winches from the equation at this point. If I need more power I can always turn on the generator which would then feed the inverters direct 120v power so they wont use the house batteries at all, but I am curious what the max amperage the batteries can supply in the current installation.

In a perfect world the boat would be wired for 24v, and none of this would matter, but I really really don't want to have to rewire the boat. I believe it would be a major undertaking.

Also not really interested in the 12v air conditioning units, I have looked at Mabru and I don't think the 8.2-12.5k BTU units are large enough for our space, plus the price - $5500 per unit makes me want to puke. Mabru is supposedly coming out with a 17k btu unit soon, but it will only be for 24v systems I believe & probably a $7k ea price tag.... What makes them so dam expensive??? R&D is pricy I suppose, it definitely isn't the parts they use to make them...

Thanks in advance for your advice/input, it is much appreciated!

[mako]

Quick question, did you say that you’re planning to install the bow and stern thrusters, or they are existing? And if existing, you have two - is that typical for a catamaran and how does that work out for you? Thanks

[fivecapes]

Is this S of A?

[JustMurph]

1. Ideally run from the batteries to the main bus, then the inverters. That is unless doing that means adding a lot of extra cable length (and therefore losses, or requiring larger cable). Isolators for the inverters will depend on how they behave when only one is turned on. If they can handle that (when configured for parallel operation), then I'd definitely have individual isolators. That way if you ever have an issue with one, you can isolate it and still use the other.

2. When running batteries in parallel the maximum amperages add up. So you'll have a 2500A capability, which is freakin huge.

[JustMurph]

I just had a look at how the MP will operate in parallel configuration. If you isolate either unit, the other one will turn off in fault mode.

Given that, I personally would still have individual isolators. Inverters should always be turned off before isolating them, so this won't cause a problem. Neither will operate until both are powered up. If one of the units ever dies, you just need to change the other units configuration to standalone and you'll be up and running again.

[GordMay]

Greetings and welcome aboard the CF, Osi.

[osi48]

Originally Posted by mako

Quick question, did you say that you’re planning to install the bow and stern thrusters, or they are existing? And if existing, you have two - is that typical for a catamaran and how does that work out for you? Thanks

We have three thrusters, and all were existing/came previously installed by the first owner of the vessel. They are nice, but heavy - I estimate the thrusters, batteries, switches, wire etc... all add up to almost 200 pounds per thruster or 600 pounds total. I plan on removing one bow thruster and one stern thruster once we get a little more comfortable with operating the boat. A single bow thruster is all we need. Need to cut some weight after adding the generator and AC

I think a single thruster is typical on lightweight, high-windage cats. Three is overkill.

[osi48]

Originally Posted by fivecapes

Is this S of A?

It used to be

[osi48]

Originally Posted by JustMurph

I just had a look at how the MP will operate in parallel configuration. If you isolate either unit, the other one will turn off in fault mode.

Given that, I personally would still have individual isolators. Inverters should always be turned off before isolating them, so this won't cause a problem. Neither will operate until both are powered up. If one of the units ever dies, you just need to change the other units configuration to standalone and you'll be up and running again.

Thanks for the reply @JustMurph

That is great news that the battery amperage stacks when running in parallel!
Now I am worried that my 4/0 cable from the last batteries, at each end, to the positive and negative bus is not large enough. 2500A is a crazy amount of current. I think the short 4/0 12" jumpers between batteries is probably ok, but the longer 6-8' leads may need to be doubled up if I run the inverters off the main buses?

Any reason to run them all to the main busses instead of off the batteries direct? It doesn't add much cable - maybe 4' per run, but it does then send alot of current to the main bus. I would hate to loose the whole house if the inverters tripped the main house fuses which are currently only 400amp. I figure adding two additional 400 amp fuses, one for each inverter, separate from the main house bus gives me a little more protection? And eliminate the need to double up the runs from the batteries to the main buses?

Thanks for checking the mulitplus parallel configuration operation, I assumed it would be something like this just wasn't sure what the one "on" unit would do. I like the idea of the redundant switches incase one were to fall. Would be much easier to isolate the "down" unit and reconfigure the "up" when wired this way. I will be adding a second switch.

[JustMurph]

Re cable sizes, you need to size them for the operational currents that you expect to see, not the peak currents that the batteries are capable of.

My process I follow is this:
1. Work out the peak load I would expect in normal operation, as well as the peak load in abnormal circumstances, e.g. inverter running at full load while all of the other big loads are drawing (but not a fault, e.g. something shorting....that's what your protection is for).

2. Now you need to use a cable size calculator to work out the appropriate sizing. I quite like this one: https://photovoltaic-software.com/so...age-calculator
The rule of thumb is 3% voltage drop, with 5% being the limit. I personally am a bit more conservative and have generally sized for 1.5% with 3% as a maximum. It also depends on what is running on that circuit and how sensitive it will be to voltage drop. Main connections to bus bars should be beefy with minimal drop IMO.

3. Next I will confirm that the cable won't over heat at that load. Being an Aussie, I use one of our electrical standards (AS3008) which gives you the maximum current that a cable can handle without over heating. There are many tables in the standard for different installation arrangements, for example a single cable in the open can dissipate a lot more heat than a bundle of cables in a conduit. In this situation you also need to think about the duty. If the load is continuous, then this is important. If it's only short (e.g. peak load of a stalled electric winch) then you could exceed the rating in the standard. This is much more important for large cables, which dissipate a lot less heat for their cross sectional area than small cables.

4. Now you design your protection (circuit breakers or fuses). This is there to protect the cable (i.e. stop it setting you boat on fire). You'll want them to be rated at or below the maximum current the cable can handle from step 3. Preferably size a bit larger so that your normal operational currents aren't just under the rating of your protection. Also keep in mind that if you have lithium batteries, they are capable of extreme currents in a short circuit situation and not all fuses and circuit breakers are capable of interrupting at such high currents. Class T fuses or similar are a good idea on anything directly attached to the batteries.

I hope that gives you a decently clear overview of the process and a few things to think about in designing any of your electrical mods. If anyone has anything else to add, please chime in.

Cheers,

J

[JustMurph]

Re the arrangement of battery cabling, especially with lithium batteries that have such a flat voltage curve it's quite essential to have equal resistance in the cabling to each battery in a parallel arrangement. In mine, I have individual cables, fuses and isolators for each battery running to a bus bar. All of the cables are identical length. This ensures that the loads on each battery are the same. Mine are 24V, 200AH, so I only have two of them. That x5 is a lot of extra gear.

There are a few recent videos on Will Prowse' youtube channel that demonstrate how much variation in load you will get between batteries when they're wired in parallel with jumpers between batteries. If the main leads are on one battery at an end, this is bad and the variation is huge. If they're at diagonal opposite ends this better, but the end batteries still take more of the load than the ones in the middle.

[osi48]

Well we nearing the end of our electrical refit, and wanted to provide an update for those in a similar situation.

First:

We combined the house and thruster banks, and now have 6ea 210ah house batteries. We separated the batteries into 3 groups of 2 with equal runs between all 3 groups and short 12" jumpers between batteries. Overall this is a huge improvement in the system and keeps the battery loads consistent between all groups. This also eliminated 3 of the isolators, and made the system much simpler. There were a lot of differing opinions on whether to keep the house and thruster banks separate, but with our high discharge lithium's we ultimately decided it was the right choice for us. So far, in all testing, we have been able to run the thrusters for longer than normal periods without impacting the bank by more than 3%.

Second:

Added a 1000a continuous buss bar for the 3 battery groups, two inverters, three thrusters, and two 4/0 feeds to the 1000a house buss bar. Each with there own appropriately sized fuse and switch.

Third:

Went with the Velair 16k btu VSD units. Max draw per unit, including the 2amp march seawater pump, is 9.6 amps per my clamps. With the VSD we see draws typically in the 4-6amp range as long as we have the unit in automatic mode, and not full blast. 32k BTU of Aircon seems about perfect for our boat, with window covers and shades down in direct sun with air temps in the low 90s we have had no issues keeping the boat cold. We have two 6" feeds off each unit, and all but one is a direct 6" dump and the other is a 6" x 4" x 4" tee. Two 6" feeds into the salon, one off each unit, each with short 18-24" runs. One 6" feed with a 60" run into the owners cabin that dumps at the top of the top of the bed. The 6x4x4 Splits off the port unit into the two guest berths one with a 4' run, the other a 10' run which seems sufficient if the salon is cool. The heads don't have any duct work to them, but with the overall circulation now present onboard they stay relatively cool. Seeing a 28-30 degree temp difference between the water and air coming out the vents in the saloon on max power with my thermal camera. If these last, they will be one of my best purchases to date. Nothing but good things to say so far.

Fourth:
We are still waiting on delivery of our northern lights genset, so we purchased a small honda eu2200i generator. We can run both air conditioning units and still have a little left over for topping batteries or running appliances (when they are on auto power mode) and are still able to leave the generator running in eco mode. With our 5 gallon extender tank we get about 30 hours of runtime. It isn't the quietest, but it works in a pinch when there is no breeze or shore power.

Upgrading our panels next, current ones are ecosolar chinese crap and have a ton of microcraking/hazing/water intrusion. I am torn between going with the pricey panels like the Solbian SR or Solara Power M series and hoping to get 4-5 years from them at a cost of around 12k. Or going with the cheaper renology panels knowing that they will probably need replacement every year or so at a cost of around 3k.

[JustMurph]

Are your panels all flexibles? What's the maximum dimensions you can fit?

[osi48]

Originally Posted by JustMurph

Are your panels all flexibles? What's the maximum dimensions you can fit?

The panels are all flexible and are installed on the saloon roof. I don't have the exact dimensions handy, but its approximately two areas each 6'x12'

[JustMurph]

Check out the Sunman 430W panels. They're the first semiflexible panel rated for commercial use (at least around here). The commercial panels (for homes and solar farms) are typically built and tested to a far higher standard (including salt spray testing) than anything that is sold as "marine", with the latest technology and for a fraction of the price. We'll hopefully be testing some of these soon.

https://www.sunman-energy.com/eArc-l...ct/details/15/