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simonsails avatar image
simonsails asked

Boat setup: 12v house bank, 48v electric propulsion bank, solar array

Hi, I am about to buy a used sailing trimaran and can't quite wrap my head around the ideal electrical setup. Any help would be much appreciated.

  • The boat has an existing 12v house bank (100ah lifepo4) which is sufficient at sea
  • All wiring and electrical appliances are 12v optimised
  • A 12v to 220v 2000W inverter is installed for power-hungry appliances
  • I've got 6 x 100W semi-flexible solar panels and plan to use 3x Victron 100 / 20 MPPT charge controllers
  • This should enable to keep the battery topped most of the time, with little electrity use at night

Additionally I'm planning to add the following:

  • 48v electric engine as secondary propulsion (sails 95% of the time)
  • 6.0KW max draw, 1.0KW max hydro regeneration
  • 8.9 KW lifepo4 dedicated propulsion battery from manufacturer

I would like to intelligently combine the two systems/batteries as I expect that usually one or the other has more energy than it needs. So a bidirectional 12v - 48v charge system / battery combiner is what I am looking to implement.

I'm aware of cyrix products but not quite sure how to implement them in a 12v / 48v system.

Thanks for reading, curious about your ideas and solutions.

MPPT ControllersCyrix Battery Combiner
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3 Answers
Paul B avatar image
Paul B answered ·

really there is no way to combine the two banks without high costs.

there are may ways to handle this none a write or wrong, some ways are better some cost more some less.

below are a few options

1 x set all the charging to go into the 48 volt bank, then charge the 12 volt bank with 48 to 12 DC to Dc chargers (check that the MPPTs can do 48 volts ??)

or

maybe the best solution is to raise the 12 volt lipo bank to 48 volts then use some 48 to 12 volt reducers, and if needed but a small 12v Lifep04 buffer battery in to absorb high loads.

but your 2000 inverter is the bigger issue due to high 12 volt bpower draw, maybe sell it

you are maybe going to have to buy a 48 volt charger anyway to charge the larger lifep04 bank from time to time, so get a 48 volt inverter charger instead.

if you go this way also check that the MPPT units you have can also switch to 48 volts, some models can some cant.


Or use a DC to Dc charger to go from 12 volts to 48

or use the inverter and buy a 220 to 48 volt charger to allways charge the 48 volt bank, this maybe the cheapest solution

Most ways will also have some form of power loss so also consider that

make a few plans and get the costs and the pro and cons

then add up the costs balance the above and see whats best solution for you


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simonsails avatar image simonsails commented ·

Thanks, that's very useful. I might just do option 1) as suggested: connect all mppt (48v) and solar panels to the 48 propulsion bank, and then use a 48v - 12v dc to dc charger.

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ralph-vallis avatar image
ralph-vallis answered ·

I have the same problem -

I think it is better to run the 48V system as the main system - I want to feed all 12V systems from the bypass line from the Cyrix or from the trigger line from the MPPT.

1. does anyone have experience with the trigger supply from the MPPT?

2. I don't have Victron batteries - want to use my old 48V banks - what is the best plan to prevent both overvoltage when charging and undervoltage when driving with the e-motor.

3. the 48V banks are always a little off - so never full - what is state of the art for balancing - if you want to install some kind of BMS (Victron BMS does not work) - is the battery coupler BCD there the solution?

thx48v-stromkreis-boat.jpg


48v-stromkreis-boat.jpg (176.6 KiB)
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ningaloo avatar image
ningaloo answered ·

@ralph_vallis

I am interested that you are using an ePropulsion Spirit Evo. I bought this as the outboard for my tender, but want to make use of the 1.2kW 48V battery to supplement/charge my 12V 480ah service bank when sailing at night when I don't have any solar input. My systems typically draw 8-10a with fridge, autopilot, nav equipment and lights.

Have you found a way of connecting the Spirit battery to your system? I understand that ePropulsion may be working on some sort of "T" connector but this is not available yet.

I am planning to use either an SmartSolar MPPT 75/10 or and Orion 48/12 9a converter. At the moment I think I will have to switch this on manually when the service bank drops low and off again when it is suitably charged OR the Spitit voltage is dropping too low. Any ideas on how this can be monitored or controlled?

Any thoughts are which might be better?

Longer term I also want to use the Evo in regen mode but haven't found a way to hang it off the transom yet!

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