Re: Lithium battery costs
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I’m sorry but I really don’t get the fascination with installing electric motors on cruising sailboats. Your 40KW motor is 53 HP which is about half the power that your boat came with (assuming your later model Super Maramu had the Yanmar 105HP). Granted you don’t NEED all of that 105HP as there are plenty of Super Maramu owners perfectly happy with their 78 HP Perkins/Volvos which would put out about 40KW at 2400 RPM but I suspect that 40 KW is stretching your ability to get off a lee shore or through some big currents. You could try it by running your motor at about 1700 RPM.
The 28Kw/h battery bank could run that 40KW motor at that rate for a grand total of 38 minutes on batteries alone but I very much doubt that your battery bank could support discharging at 1.4C (most Lithium Ion installations restrict to 1.0C and that’s on the extreme end IMHO). If you also fired up your new 18KW generator, it drops your C rate to less than 1 and you could double your longevity but 76 minutes of power (assuming your batteries were already fully charged AND you starting the genset the instant you turned on the electric motor) is not nearly enough IMHO to satisfy basic seamanship requirements even for just coastal cruising.
That’s a huge cost to get a significant reduction in capability and I think would dramatically lower the resale value of your fine boat.
I get the urge to electrify everything but are you really getting that benefit if you have to run a diesel genset at the same time? It works for cars because they can carry huge battery banks (the Base Tesla model 3 has a 50KW/h battery pack of NCA (Lithium Nickel Cobalt Aluminum) cells that are designed to discharge at high C rates unlike the LiFePO4 cells used in boats for safety reasons). Of course that means that they are a lot more susceptible to bursting into flames so not a great idea on your floating home. Also a model 3 car at 60 mph/100 km/h only uses about 0.34kw/h as most of the power is needed to get it moving and they can regenerate that kinetic energy when braking and coasting which can’t be done in a boat - although admittedly you could put a hydro-generator on to help recharge the batteries when sailing - but of course that won’t be of any use when you have to motor. Still, that 50KWH battery is only good for 151 kms of range according to Tesla’s configurator… they want you to upgrade to the 82KWH battery to get 500kms (300 miles).
We had a good example of the difficulty of doing this in sailboats with one of our recent guest speakers, the estimable Jimmy Cornell having to give up his attempt to sail across the Atlantic (let alone the world) on his specifically designed and completely solar bedecked Catamaran earlier this year. They said that they dramatically underestimated the power consumption and overestimated the generation capabilities- and that’s with a team of sponsors well motivated to make sure of his success. He’s now going to try again but only after significantly upgrading the solar, hydro generation and efficiency of his consuming equipment. An Amel can’t carry the same amount of solar as a specifically designed cat and they need more power to move them than a performance cat as well.
It’s your money but I don’t get it. I guess you’d save a lot of diesel because you’d not be able to motor anywhere anyway. LOL. If I was that worried about saving carbon, I think I’d pocket the money and stay on the dock. :-)
On Sep 5, 2021, 10:10 AM -0400, Andrew & Kate Lamb <andrew@...>, wrote:
Future Amel Owner & Amel Owner Registry Moderator
Oro-Medonte, Ontario, Canada