Electric Drive

With Electric Yachts of Southern California’s Mike Gunning’s expert assistance, Sine Metu is being refit with a 100 ibl Quietorque™ electric drive system (March, 2012). While the reasons behind this refit are numerous, it all starts with the fact that the original 8 HP, Farymann Diesel was nothing more than 150 pounds of unrepairable, rusted scrap iron, not to mention its dead fuel system and a dangerously neglected  raw-water intake through hull (which, by the way, broke off in my hand as I was replacing it while hauled out in July, 2011)…did I mention that I bought the sailboat for $800? In its place will be a 48 volt, 3.5 kw, brushless electric motor that’s powered by three banks of LiFePO4 Lithium batteries with 120 amp hours of near-silent muscle.

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48v, 120 Amp Lithium Battery System

The battery configuration consists of a dozen Valence UX-P, 12v, 40 Ah Lithium LiFePO4 batteries. With three banks of four batteries wired in series, then in parallel, the system will deliver 48v at 120 Ah. Ideally, the system will provide the capability to motor at top speed – theoretical hull speed – for over five miles;at two-thirds power, I should have a range of just over fifteen miles. And as an auxiliary engine for a small pocket cruiser, that’s pretty damn great considering that I also gain an extra cockpit locker (removed the fuel tank); can quietly “motor-sail” for hours at a time (thus maintaining my top hull speed if the winds are a little fickle); and never have to worry about smelly diesel fumes, oil leaks or spills at the fuel dock. As you can see by the following chart, nudging the engine for a couple of extra knots of power while sailing can be done for 12 or so hours – which translates into an extra 43 miles of distance.

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And, with the system being “refueled” as I sail either through Regeneration (prop spinning due to the force of the water (maybe, if I am lucky, this will add about 5% to the fuel tank)), a wind generator and possibly even a solar panel or two if I can find a place to place on this tiny cruiser, I will constantly be refueled as I cruise the Pacific.

Yes, the initial costs are steep, but the long-term costs are dramatically less and I’ll never have to worry about the price-per-gallon, having enough cans of motor oil stored aboard, fuel filters (and spares), and on and on. With this electric engine, I will have to sail more than motor…Wow, that kind of sounds dumb, doesn’t it?

It’s a sailboat. The goal is to sail as much as possible. The eDrive is for docking, entering harbors and bays, anchoring (you need to back down and set that anchor!), and… Oh Hell, starting with Joshua Slocum’s circumnavigation of this bright blue planet, alone, without an engine in 1895, there is a lot of precedence for what I plan to do.

Also, since each battery weighs in at about 15 pounds (7 kilograms) each, roughly 185 pounds of weight will now be more evenly and logically distributed low inside the hull and improve stability.

As a rough comparison, here are a few weights of each system’s parts:
8HP Farymann Diesel (dry) – 150 pounds. 15 gallons of diesel fuel – 112 pounds. Wet-exhaust system – 15 pounds. Minimum weight of 277 pounds.
100 ibl Electric Engine – 52 pounds. 12 Lithium Batteries – 185 pounds. There isn’t exhaust – 0 pounds. Minimum weight of 237 pounds.


As you can see, converting from diesel to electric is not about reducing the overall weight of the sailboat’s drive system, that’s just a little bonus. But keep in mind that the single heaviest piece of equipment is now the motor itself at 52 pounds (23.4 kg), which is manageable for one person to deal with if needed – which, frankly, will not be very (if ever) often. Doubt me? Well, keep in mind that you already use an electric engine every time you start your fossil fuel engine…the starter! And when was the last time you took that in for a tune up or an oil change?

And if I can figure out how to embed video into this WordPress blog (never mind, it’s not worth $59 – yikes!), here is one I shot January 28, 2012 at the San Diego Boat Show of my actual engine! I let Electric Yachts of Southern California use it as a demonstration unit as I cannot install it for a month or so (redoing the cabin sole right now, but I am traveling too much to make a lot of progress on that right now. So, in the meantime, I have the flooring ripped up and I am airing out the bilge while I’m gone).

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In the next article, I will discuss…
Battery Management System (BMS)

DC to DC Conversion (48v to 12v)

LiFePO4 Lithium Batteries

There will be 4 batteries just aft of the engine compartment; 4 batteries in front of the engine mounts; and 2 batteries on each side of the electric drive.
System will consist of 3 banks of 4, 12v batteries series for a 48v, 40 Ah bank. All banks will then be run in parallel to bring amp-hours up to 120 Ah at 48v.

Below are scans of the battery data sheets that I picked up at Valence’s headquarters in Austin, Texas, while I was there on business in August, 2012. I also learned on that visit that my batteries were their first generation batteries – they are now (as of this writing) on their third generation.

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Wiring Diagram

Tentatively, the battery wiring will follow the following diagram — NOTE: Where it indicates ‘Inverter,’ that’s where the edrive and charger are attached via individual pos/neg busbars.

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