Main Sail: I bow to the logic in your calculation, however, I challenge the summation that a sailor (emphasis on sailor) would need to motor more than 20-30 KnM in a day without being able to raise his or her sail.
Based on available data the average endurance of the batteries traveling 20 nautical to a 50% discharge level and 30 miles to a 75% discharge level.
That summation was straight from your post.....
I was just using your own data points figuring you expected performance like that.
If my summation is correct, then during this period of time the vessel is motoring under electrical power it is still recharging via solar, wind or kinetic energy. Also based on the assumption that during a 24 hour period a sailor is able to alternatively raise sail and/or motor the boat that there would be sufficient reserve energy to operate the vessel. Likewise, in cases of emergency a diesel ginset could recharge the battery bank.
Do the math on this please.. Regen, wind or solar take a long time to replenish even mild use of an electric engine unless your entire boat is covered in solar panels.
Argument 2: the cost of engine overhaul/rebuild - over the course of just a few years the Diesel engine will cost more to maintain than the initial cost of an electric engine and batteries. Another given is that technology will drive down cost and increase efficiency of battery life. Electric engines have very little maintenance. I admit I don't know how long they last.
I am pretty anal about maintenance and I spend perhaps $100.00 per year on filters & fluids. Electric engines are low maintenance until they just stop or corrode. Corrosion is the big killer in ocean sailed boats. Some EC's are much better than others... Still you can do it on the cheap...
Argument 3: the price of fuel is a constant variable - if there was a fuel shortage it might mean you can't get fuel. Or in the worst case scenario - civil unrest does not permit you to safely stop, an electric engine might just save your bacon.
If we get to that point we have more to worry about than "yachting"....
Okay - most day cruisers are traveling the globe - then it's not a problem to stop for lunch or dinner while they recharge.
Unless you have Lithium, and a massive charger, you are not recharging over lunch. Simple physics.. It takes 6-10 hours to fully charge most flooded lead acid batteries and get them to full regardless of the current source. Once the batteries hit absorption voltage the current flows in very slowly...
Argument 4: self sufficiency - I'm sure there are a few Doomsday prepares that would argue this point much better than I could possibly. Plus it's quite, meaning you can sneak into and out of port.
The doomsday prepper argument? Now that's a new one on me and I have some customers who are real fanatical about EC's...
Again if get to the point where we need to sneak into and out of a port under the cloak of silence the last thing we will be thinking about is "yachting"...
Argument 5: noise, environmentally cleaner, air quality - let's face it, things are different and eventually they will crack down on marine environment taxes.
Yes it sure is quieter and to me that is the biggest benefit. I personally don't believe is is cleaner or greener. Replacing batteries every few years? Green? Charging lead acid batteries is horribly inefficient and your use of inefficient charging means lots of waste energy which may come from a coal fired plant. IMHO an EC is a
feel good green. If it makes you
feel green, then I say go for it.. This is coming from a guy who drives a Prius, which is also
feels good green, for many owners. Course I don't drive it because it is
feel good green, it is NOT GREEN but it sure does save me money on fuel....
I also love the technology and the amazing reliability of the vehicle...
I am sure the couple in the cold molded custom built 22' cat boat we ran into tied to the dock at Bucks Harbor a couple of weeks ago was making the same arguments. The boat was stunning, designed just for them and a true one-off build. They were charging at the face dock when we got there at 6:00 pm (we don't have many marinas up here so a special exception had to be made to allow them to charge.) When we left the next morning they were still there with an extension cord plugged in, charging. They killed the bank and had to be towed in, according to the lady on-board whom my daughter & I were chatting with. I don't know what they paid for the tow but I do know from talking with them the system was not meeting the "expectations" they believed. This would not be the first time an e drive system did not meet the
expectations of the owners...
This is why I say to do the
real math. Look beyond the rose colored lenses and make an educated decision from a mathematical perspective not from the "heart"... Doing so will result in a better system that DOES meet your expectations. This is the most critical aspect I see surrounding EC's, removing the
ideals from your
heart and moving the decision making where it belongs which is up to the
brain...
On a related note I have a customer ripping out a composting toilet this winter after I heard about how great it was going to be for two solid years. She got way to
idealistic and the composter completely failed to perform for her
intended use. This stuff happens, especially when you let your vision or idealism cloud the picture. Everything I had pointed out to her came true. An no I have not done an "I told you so" as I don't need to rub salt into the wound.. Some people just need to learn by trial and error...
She is now faced with re-installing a new sanitation system, re-installing seacocks she paid big money to glass in etc. etc. etc...
All I suggest is looking beyond the glossy feelings about an EC and dig into the real data to make sure it fits into your box and your desired use. I only used 20-30nm because you did. If that is not your box then figure it out and design a system than will work for that, if it can. So your homework, do the math, learn Ohm's law, learn about batteries, Coulombic efficiency, Peukert etc. etc. etc... Spend more time on the
science and less on the McDreamy aspecs of the EC and you will get a better system...
We
non-real sailors don't often plan on motoring 30 miles, we would always prefer to sail, but up here in the land of 10'-25' tides, solid granite ledges, zero wind for multiple day stretches & pea soup fog the DC energy can run in short supply unless you don't mind bobbing around solid granite ledges in pea soup then sometimes you may need a range of 30nm...
Other areas or lakes are a far better fit for an EC than here in Maine but it still can be done if it fits the box for the intended use... I don't know your waters or use so can only suggest you do as much homework as you can.
Again EC's
can & do work if you fit into the box. Unfortunately most
cruisers do not... Lakes, dock tied at night etc. work best. Too many I have met come across or even my own customers tend to get idealistic about the fantasy of electric conversions, composting heads etc. and a couple have been burned badly. It
can work but please do the math and homework so that it meets your expectations...
Battery technology is already here in LiFePO4 but budget conscious EC conversions do not fit in this box. The LFP bank & BMS alone can cost more than a new diesel but these are batteries that if charged and discharged correctly can likely last 12+ years in an EC. The battery technology is here, but it comes at a price.
If I had a day sailer I would probably put in an electric engine, just because, but the bank choice would be definitely LiFePO4. I would not personally even consider a lead acid bank for an EC for my own vessel.
