Brian,
Welcome to the list. I first want to say that my answers are general and one can find exceptions to everything I've said here. But these answers are valid for many of the installations done by people on this board.
The simplest way to convert your boat will be to emulate the Farymann and use your current shaft and prop. Most diesels have gear reducing transmissions with ratios around 2:1. That means that the propellor shaft spins at 1500rpm when the engine is running at 3000rpm. Many small (5kW and smaller) electric motors hit their max rating around 3000rpm and need that speed to facititate cooling. So some sort of reducing gear is recommended, this can be a gear box, belt drive or chain.
There are 2 typical conversion factors that are used around here. The first is 1hp electric = 2 to 3hp ICE (internal combustion engine). I prefer to use 2.5 for rough estimates. So a 12hp engine translates to about 5hp electric. 1hp = 750W, therefore 5hp = 3750W or 3.75kW. Alternatively, since boats are often overpowered or underpowered for various reasons, a more consistant covnersion is 1kW per ton of displacement. The specs that I found on a Cascade 29 list it at 8500 pounds. That's puts your power requirement right around 4kW.
So now you're looking at a 4kW drive, probably with reduction, so far so good. Now, let's look at batteries (storage).
A very general conversion to get you into the ballpark is 11.5kWh of usable charge = 1 gallon of diesel. Your 4kW drive will probably be 48V. A 12V battery rated for 240Ah contains 2880Wh of energy at a 20hr rate. Four of these batteries should equal 11.5kW (4 * 2880Wh or 48V * 240Ah). But this means running the batteries to 100% depth of discharge(completely dead). Different types of batteries have different recommended DoD for long life. Many people use 60% DoD for flooded batteries, 70% DoD for AGM and 80% DoD for Lithium. So you're going to need more storage to get the equivalent of 1 gallon of fuel in your tank. Without going into much more math, I would recommend AGM as a reasonable compromise between capacity and cost. You'll need more than 350Ah at 48V of AGM to consistantly deliver the performance of 1 gallon of diesel at slow speeds. In my 30' ketch I accepted that my battery bank is equivalent to about 0.6 gallons of diesel, which matches the way that I use my boat. Like you, I own a 2000W portable generator to extend my onboard range, if needed.
Regen is a tougher problem. While many systems have regen capabilities, I've heard no verifiable reports of more than 100W at 5kts. That's less than 2A charging into a 48V system. Since regen is extracting energy from your speed, it does slow the boat down some. You know best about how often you can keep your boat above 5kts, but my 30' ketch hits 6kts rarely. So regen might help under long passages, but for day sails, the energy collected on our size boats is typically pretty low.
Wind is another source that sounds better on paper than in practice. You need decent wind, just to get the charging started and any downwind work effectively shuts down whatever is available. From multiple reports, solar is much more effectivve for our boats. I would focus there first.
I know this is a lot of info. If you're not in a hurry, you'll absorb additional info just reading the posts on this list for a while and asking just one question at a time when you need clarification or more info.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "brianmisner@..." <brianmisner@...> wrote:
>
> Hello All,
>
> Brand new to the group, and please forgive me if this thread has been talked about(and I'm sure it has). I have a Cascade 29 that is currently powered with a 12 Farryman, single cylynder (very annoying). With the 33 gallon fuel tank and the engine/trans assembly gone I would have a tremendous amout of room for banks/motor/controller.
>
> Would a typical golf cart 36v or 48v set up work or would I still need a reduction assy? Will these set ups re-gen? I have shore power available for charge, as well as a 2KW gas genny. I could easily add wind/solar. No off-shore work. No extended motoring periods (Columbia river) Also I'm not sure how long a typical golf cart batt bank lasts. The boat is easily run up to hull speed with the farryman and a 12x 8, dbl bladed prop (could probably fit 13").
>
> Obviously, on a budget with the current state of things. Any help getting me pointed in the right direction would be appreciated.
>
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