I'm currently looking around to buy a sailing-yacht and plan is to convert slowly convert it into a electric/hybrid setup and need some advice. Writing a long introduction to convey my initial thoughts and ideas, and what i see as possible issues.
What i'm currently looking for is a ~40-45ft steel yacht (~14000-16000kg). Fiberglass would be lighter, but my preference is steel due to a multitude of reasons.
I will be looking for boats that have no functioning motor or that will need a replacement soon since that will reduce the price quite significantly. ( 10k EUR or so for a new diesel motor and all that it requires )
My use-cases are:
- Silence .....
- Large enough battery-bank to switch to using induction cooker / electric owen.
- Allow to stay offgrid for much longer periods. (Electric watermaker etc)
- Motoring in and out of marinas/setting anchor and such.
- Instant engine power and much lower, steerable, speeds possible.
- Higher reliability of a electric engine for propulsion so even if the genset breaks there would be enough time to get to a safer place (drop anchor etc)
- Have a large enough battery bank that would cover at least a week without sun or running the generator. (~5kWh per day ~35kWh for a week )
- Genset to allow recharging as a fallback when without sun.
- Genset to allow longer distance motoring, even if a bit slow.
- Since there is no need to think about propeller-shaft etc i could place the genset and fuel-tank wherever i want, like on deck in an encapsulated box.
Power to propel a boat like this at hull-speed would require somewhere between 25-35kW but lower cruising speed would only be 3-8kW, in light wind, when up to speed.
Target RPM for the prop should be around 800-1000rpm
Batteries i'm thinking about are reclaimed Tesla 5.3kWh modules from a 85kWh pack ( 225Amp continuous, 22.8V nominal, 25.2V max ) and 12 to 14 modules depending on selected voltage and such.
48v - easy to source components for marine environments but having issues locating sensibly priced motors/controllers. [email protected]
96v - still possible to source components, but starting to be difficult. Starting to be easier to locate BLDC / AC motors ... [email protected]
144v - quite hard to source components, but starting to be easy to source motors.. [email protected]
168v - very hard to source components, but starting to be easy to source motors.. [email protected]
All the above variants should be possible to handle with the tesla battery modules. (Max current for 30kW used in calculations)
48V = 14 modules in a 2s7p setup would result in 89A (max) per string
96V = 12 modules in a 3s4p setup would result in 78A (max) per string
144V = 12 modules in a 6s2p setup would result in 104A (max) per string. If one string fails the remaining string will have to provide 208A and that is also quite doable.
168V = 14 modules in a 7sp2 setup would result in a 89A (max) per string. If one string fails 178A is still doable on that string.
I do prefer having 3 or more strings for redundancy (failing Pack/BMS/cables etc) since this would be a combined house and engine-bank. Each string should be individually fused and possible to isolate from the rest in case of a fault.
Power generation would consist of multiple setups:
- Solar ~1kW of usable ( ~2kW but only half would probably be usable depending mast-shade etc )
- Hydro generator ~200-500W when sailing. ( preferably via regen of the motor instead of a drag-able generator)
- Diesel generator(s) .. 1 or 2 generators with a capacity of ~5-6kW each.
Still researching solar-panels and how they could be setup, but 4x400W panels on the back arch + 2x400W that are manually moved around when at anchor. 4 panels @ 45V = 180V so on the edge if going with a 168V battery-pack.
144v and below should be doable either way, but still hard to source components. Possibly finding a good
MPPT charger with boost functionality, have so far only found crap Chinese versions with contradicting specifications.
If we go the other way and only do 48v for everything we should be able to use known quality brands of MPPT controllers, 220V inverters and all the other stuff needed on a boat, and possibly reusing what's already installed.
One possible motor could be the [email protected]
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One thing i have been looking for, but have not found any so far, is if there are any AC or BLDC motors with thru-shafts that could enable stacking multiple 48v motors together, but not sure on how complex the controller setup and such would be in that setup, especially with regen.
Solarpanels / MPPT chargers / 220V inverters / generators etc are still required and not included in the total price of this conversion, if we stay at 48v.
Rough estimates of prices, if i go 48V with the AC motor i linked to:
Tesla battery modules ~1000EUR each if buying 12-14 modules. ~14000EUR.. Have not search too much yet so may be possible to get cheaper.
BMS 100EUR - reusing the built in Tesla BMS boards and only adding a controller.. ( See GitHub - collin80/TeslaBMS
contactor(s)/fuses/cables etc ~2000EUR
= ~14000 + 2000 + 100 + 10% = ~18000EUR
+ whatever motor + mounting is needed ~2500EUR
So a total of somewhere around 20,000EUR should be possible.. Maybe a bit lower if finding cheaper Tesla modules or going with less capacity.
.... So now... Tear my ideas to pieces and suggest other things that would work better or would be cheaper!