Excellent summary!
Capt. Carter
www.shipofimagination.com
On Sun, Aug 12, 2018 at 11:18, king_of_neworleans<no_reply@yahoogroups.com> wrote:
Just getting in and out of harbor is where electric propulsion really shines. When you need long range, things get awkward. The obvious way to extend your range is with a bigger bank. However, there are practical limits to this imposed by the hull on the weight and volume of the bank. For a boat your size a bank of 8 6v GC2 golf cart batteries is relatively cheap and wont bring her down in the water too much, considering you are also getting rid of fuel tank, diesel engine, transmission, and associated wires, pipes, filters, hoses, pumps, etc. That would give you better than 10 kw/hr of storage, of which half would be available to you if you discharge down to the commonly accepted limit for long battery life. These batteries are the cheapest way to go, if you buy them from a big box discount store or golf cart supplier. You get more available storage for less weight by going with Lithium Iron Phosphate prismatic cells such as the popular Winston brand. Lithium Ion cells are popular but there are inherent safety risks that are addressed by fusing individual cells and using a BMS, on which you must rely to hopefully prevent a catastrophic FIRE. I have not heard of a LiIon battery fire on a boat but just know that the possibility does exist. LiFePO4 prismatic cells are available in very large sizes so you do not have to parallel wire them, just series wire. They are, however, quite expensive. A second bank or more batteries in parallel will extend your range x2 of course, while also doubling the weight of batteries, a negative consideration, probably, with a 26' boat.Another way is to go slow. Want to go 5 kts? Your range will probably be less than an hour's run with a reasonable size bank. Okay with 1 kt? How does 90 or 100 miles sound? (typical but varies wildly of course with the boat and the batteries!) A happy medium is about 30% of your theoretical hull speed. At that speed you are probably consuming power at around the 20 hour discharge rate, giving you the rated capacity of most Flooded Lead Acid Deep Cycle batteries, and you are not pushing a lot of water ahead of you. Too slow? Maybe EP is not for you.Range extenders such as a 2kw portable gasoline (petrol, for you Brits) generator are inefficient but are a good backup for when your bank is depleted to the 50% mark. Note that Lithium batteries can be discharged much more deeply without harm. I am talking about FLA batteries. Solar panels are another option. If you really try, you can probably get quite a bit of solar up. The prime real estate is off the stern, where at least some of the time your panels are totally unshaded. Shading of panels will hit energy production HARD. Also cloudy weather will reduce your solar harvest, and you can only count on max solar power for about 3 or 4 hours a day, and it will probably be significantly less than the rated output.So how much range do you need?
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Posted by: Carter Quillen <twowheelinguy@yahoo.com>
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