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Refit electrical system 35ft/11m catamaran with LiFePo4. System recommendations anyone?

Lady Rover

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Joined
Mar 21, 2021
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Hi,

be aware this is a detailed & lengthy post ;-)

We are about to renovate the electrical system onboard our 35ft (about 11m) catamaran.

At first some input on the boat and circumstances & attached two graphics showing our planned system and a load balance of the proposed system (Excel format, zipped, feel free to copy and use it also for your own purposes, I give no guarantee though for it being correct and take no responsibility for terrible things which might happen from its use ;-) , followed by questions we have to the knowledgable folks here.
Please be specific when recommending equipment (= Links or exact model numbers). Please keep in mind, we are on a tight budget, but we are aware that we need to invest into some stuff when moving onboard, even though it might not be Vitron this time around due to budget.
I know the phrase buy cheap buy twice, but if you can not buy expensive right now, you can at least go cruising right now.

THANK YOU SO MUCH!

THE BOAT:
35ft Catamaran.jpg


CIRCUMSTANCES:

  1. We will live more or less permanently onboard.​
  2. We intend to cruise only in warm climates.​
  3. We are from Europe, so our AC system is geared towards 220V and ideally we buy stuff from European suppliers.​
  4. Typically (80-90% of time) we are preferring to anchor instead of going into marinas.​
  5. We are on a budget & prefer to change only the components we really need to change to make the planned system with the LiFePo batteries work.​
  6. Our current batteries are pretty much shot and as space & weight are equally an issue as budget is, we intend to get 2-3 sets of these: https://bit.ly/3cRAiJr as recommended in this video https://bit.ly/3r8wOHN.​
    At 460€ per set including shipping to Germany they beat AGM an Lead Acid easily.
    We are aware that there may 1-2 faulty cells in the delivery which might need immediate replacing, but feel its a risk worth taking.
  7. Our current system is completly 12v. As we do not intend to run high current items from the batteries, we currently do not intend to switch to a 24v system.
  8. As I am still working in computer graphics (www.das3Dstudio.de) and will continue doing so from the boat, I need to power my high performance PC.
    We thought about doing this with solar, but, the power draw will be to much. We will use solar though for our house battery system.
    A less power hungry machine is not an option, quite the contrary, I may eventually need to add a second external RTX2070 graphics card.
    So looking at other options we decided to get a small Honda EU 10i genset dedicated to this.
    It will be much more quiet than our main genset, as it can power the PC in Eco mode.
    Fuel is not an issue either, as our main engines as well as the main genset run from petrol anyway.
    We will eventually add third LiFePo4 pack to run the work PC occassionally overnight.
  9. We do NOT have diesel engines and alternators.​
  10. Batteries will be located on the bridgedeck but within living quarters, so lead acid is pretty much out as a solution.​
  11. We do want to keep our existing fridge ;-)​
  12. We will add the separate freezer.​
  13. Our current genset is fine for running the desalinator and power tools or even a heater, but it is to loud to run the work PC over extendet times.​
  14. The Starlink antenna is planned in for business later, but currently not yet available for mobile platforms and their planned mobile unit might be slightly different. Currently they say the antenna daws 100w.​

QUESTIONS (Please suggest specific models & (possibly European) suppliers if you can):
BMS

a)
We need a battery management system (BMS) for our batteries. Our intendet battery packs have 280Ah each. Charging will happen mainly via the four solar panels and the windgen.
Is this one https://bit.ly/2QlydxL suitable?
b)
I understand we need to „top level“ the cells before starting to use them. Should/do we need to also install an auto leveller?
We prefer to have less risk if we forget to to switch something on.

SOLAR CONTROLLER
a)
We have two Sunware Fox100 Solar controllers from our old solar panels. Do we absolutly need to change those, or can they be reused with the new 300w panels?
b)
If we need new controllers what are suitable controllers which are good but do not carry the pricetag of the Victron units? Please suggest specific models suitable for our set up with four 300W panels. Remember we are on a budget.
c)
Do we need one solar controller per panel?
d)
Our Rutland 1200 Windgen controller (Manual here https://bit.ly/394RuKC) has a solar controller terminal too and can accept up to 20A from the panels.
Can/should we use it to also control one of the PV panels?

SOLAR PANELS
For now we will get 4 new 300w panels. We have no issue using industrial grade panels as long as they are saltwater proof (which they also need besides Highways...). We prefer hard non flexible panels. Open to suggestions.
While looking into this, I found this pretty handy site by the European Union: https://bit.ly/316K2Kg
Some may find this helpful too.

CHARGER
We currently have a Dometic Waeco 1250 50A charger to charge via Genset or Shore power. It can handle 220V & 110V AC input.
a)
Do we need to upgrade it? As far as I understand it can be used for LiFePo4 charging when the dip switches are set accordingly.
b)Usually we plan to charge from solar and wind, the charger is a back up. So 50A from it should suffice. No?
c)
On the odd occassion on which we are actually in port we are usually docked for several days, so the 50A charging should suffice, no?LiFePo4 are said to pose less risk fire/explosion risk than standart LiPo batteries.
Still, is it a good idea/a necessity to use a metal battery case?
Maybe with a non combustible insulation of glass cloth inside facing the battery cells.

STORAGE
What happens if we need to leave the boat over an extendet period? In the past with AGM we could simply leave the batteries hooked up to solar. Is that possible here too? Or should it be done different?
 

Attachments

  • 35ft Catamaran LiFePo4 Charging Schematic Rev00 2021-03-15.jpg
    35ft Catamaran LiFePo4 Charging Schematic Rev00 2021-03-15.jpg
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  • 35ft Catamaran LiFePo4 Consumer Schematic Rev01 2021-03-17.jpg
    35ft Catamaran LiFePo4 Consumer Schematic Rev01 2021-03-17.jpg
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  • 35ft Catamaran Electric Balance Liveaboard Rev00 2021-03-15.zip
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I would replace your invertor with a charger/invertor like ones from victron.
 
Due to the higher resting voltage, the SI ACR (shown in your first attachment) will never disconnect from a LiFePO4 bank unless the SOC drops below 20%.
 
Thanks for your answers!

@All
Does anyone else have specific answers to my questions by any chance?

@wargames
I'll write an Email to Dometic Waeco & Victron to get their input as well.
Question, are there any reasonably priced alternatives. The Victron stuff seems very good but very pricy too.
Which Victron charger model would you recommend as a good not overspecced solution?

@sprint2freedom
What is the SOC?
The Yamahas charge output is 6A each @ 12v. So not that much, but, it would be nice to feed that into the main battery as well and not only into the starter battery.
Still if its to complicated we accept to have the 9.9hp only charging their respective starter batteries and not connecting it to the main battery bank.
In this case we would sell the ACR to someone who needs it.
 
SOC = state of charge.

The SI ACR is designed for lead acid voltages and will not perform its advertised function with LiFePO4. Rather than connecting or disconnecting when a charge source is present or absent, it will just stay permanently connected regardless unless the battery bank is significantly depleted (e.g. the pack voltage drops below 12.75V or ~20% SOC).

Because of this it will be a constant drain on your electrical system.

I don't even have a LiFePO4 system, I'm just pointing out a problem with your proposed schematic. I have same SI ACR as you do in my lead acid setup and have been wrestling with how to replace its functionality when changing to LiFePO4.
 
Re the ACR/VSR - you could simplify things quite dramatically by going a combined DC2DC charger with built in MPPT This way you eliminate the VSR and the Solar controllers - given the output of your motors you would not need a big dc2dc charge rate but may need to oversize it for the solar. Alternatively you could go for a small 20a DC to DC charger solely to replace the ACR/VSR unit. The DC2DC chargers have lithium profiles so charge correctly in multiple stages. The only caveat I have found is that I need to put a HD relay in front of mine with an ignition feed, as they will continue to draw from the crank batterys if they are float charged. The relay will disconnect the DC2DC from the crank battery. ( I run dual engine, dual crank battery and single house bank. Crank batteries get float charged - 4a charger) and house gets hit with Victron 12/3000 charger inverter at 120a - The 2x DC2DC i have chosen have up to 800w solar input each.

You mention you are on a budget (we are also) however in the long term my new set up with lithium should last for at least twice or even 3x what AGM would last at around 50% more than AGM and we get a smaller, lighter battery and more reserve than we had AGM (300ah useable at a push vs 326ah with lithium) The investment is hurting now.. but i'm confident it will pay off :)

Steve
 
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