Electric drive isn't for everybody. In very demanding applications, there can be issues with range, or reserve power. For someone who only needs power for a few minutes when leaving or arriving at the slip, I feel that electric drive is the best possible solution. For someone living off grid with modest propulsion needs and plenty of wind and solar, electric makes sense. When the safety of the vessel depends on being able to punch through heavy seas for hours, I think electric would be perhaps not as good as a diesel. One way around that would be to go electric, with a decent sized diesel genset to start up when the batteries are low. There are some very powerful electric motors available, but the problem is storing enough charge in the battery bank to run it at power for more than a half hour or an hour. When low power is useful, a decent bank can keep you going all day. Big difference between motoring at 3kt and motoring at 7kt. The first thing to consider in selecting a motor type is whether you have any propane or any gasoline accessories onboard. You do not want any brushed motor if there is any chance of flammable or explosive vapors collecting below. This would definitely rule out a brushed DC motor. BLDC or Brushless DC motors are very popular in boats 35 feet and smaller. There are also different types of AC motors. A motor controller is also needed, though it is possible to run a brushed DC motor straight from the batteries in an emergency, and I assume an Induction AC motor could in a pinch be run straight from a heavy duty inverter. But normally a controller is needed for any of these motors. For a BLDC motor you need a BLDC controller rated for the voltage and current. One possible solution would be a Montenegro 0913 motor and Kelly KBL series controller. Kelly has a kit I think for this motor and a 72v bank that is pretty cheap. The motor will cost around $700 to $780. The Kelly kit is I think another $1200 or so. For this motor and your prop you will want a reduction of some kind, either a planetary gearbox or a belt or chain drive. Thunderstruck sells a belted reduction gear, 2 to 1, that ought to work. You can experiment with different pulley sizes to find the optimum ratio. That's the cheapest practical way to go I think. For more money you could go with something better, yeah. The Lynch motors seem to be making friends these days and possibly you could drive your prop direct from the motor. What RPM did your old motor turn your prop? Depending on load and voltage, most motors run best in the neighborhood of 3000RPM. The Lynch I believe runs nicely as lower speeds. Golden Motor has watercooled models and so could probably run safely at lower speeds, but remember that any heat dissipated means wasted energy and inefficiency, so it is better that the motor run cool because it doesn't produce much heat, than producing heat that is removed by the cooling system and discarded. Really, there are too many options for me to list here with regard to motors. I have heavily researched only the Motenergy BLDC motors. Of course the kit makers will use data from good conditions. What else? They aren't lying, but you should still be slightly sceptical, and not expect quite the published percirmance, speaking in general. This of course goes for batreries, too. AGM Batts are great! Best storage for the money, though, is deep cycle lead/acid wet cell batteries, though. They can spill. They have to be right side up and properly oriented. They are heavy. But for a displacement monohull sailboat, they are just more ballast. Weight of a typical day bank is just a couple hundred pounds more than the engine and fuel tank you took out, so only a modest weight gain, anyway. Depending on how you use your boat, 200 amp/hours or a bit more would be good. Remember that the Batts are rated by their 20th hour discharge rate. Your results will not be so good. Also you shouldn't deplete your Batts to below 50%.So your 200ah bank might only give you a usable 80ah, something like that. In other words, 80 amps for an hour, or 10 amps for 8 hours. The biggest common size is 8D, which are around 150lb each or about 72kg I think, 21" X 11" X 11", and 240 ah or so. That means you could have over 100ah at 48v of usable power with a battery weight of 600lbs and a cost of $1000 to $1800 depending on brand. With AGM the weight is significantly less, and you can mount them much more freely, but they will cost more. It is difficult to get good levels of regeneration charging from a typical sailboat. At typical sailing speeds, you can't turn the prop fast enough, with a load on it. A fast boat or the right prop makes a difference. Remember also that any load keeping the prop from spinning freely adds a lot of drag, reducing speed. You would do well to prioritize other charging methods such as wind or solar or a generator. For short distances and day sailing, charging from shore power is very economical. Yes, regeneration is real, but it would take several days of hard sailing to charge up your bank. I am starting my own electric re power in 4 weeks or so. I spent over 2 years researching. Take your time and don't rush into this. Do your research before you start buying stuff.
M 416-270-4587
Posted by: Dominic Amann <dominic.amann@gmail.com>
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a New Topic | • | Messages in this topic (5) |
No comments:
Post a Comment