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This has been discussed on several other forums. We are interested in electric propulsion for our Tiki 46 and have been in touch with several builders who have installed e-pods, etc. However, does anyone currently using electric motors for propulsion have a report on the practicality of the current products?
There's been alot of discussion regarding the weight of the batteries as a limiting factor, the best (and worst) power regeneration methods, the best (and worst) products currently available.
I don't want to summarize it all here, but I would like to open the discussion and see if there is any further interest within this really knowledgeable community in brainstorming how this might (or might not) be worthwhile (and cost-efficient). I'd be interested in any aspect of electric propulsion anyone might want to discuss, from recharging batteries to the best placement of electric motors and the pros and cons of the overall concept. I received an email from some builders who are using e-pods with their Pahi 63 and say they are really pleased with it. Ther

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Cynthia and Jean-Paul welcome in this Wharrambuilders site and thank you to share here your own experiences.

Present time the batteries are the only way to store electric energy on board and unhappily the ratio weight/volume/energy stored is very poor compared with the hydrocarbon energy. It's why I think necessary for long cruising to install an hybrid system : diesel + electric engine in serie or parallel according your personal options and preferences.
It's not possible to produce your diesel when sailing but it's possible to produce and store your own electric energy and for me it's the main reason to have electric engines on board able to produce electricity when sailing. So it'll be possible to stay a lot of months in isolated islands without the need to sail in a main harbor to buy some diesel.

It's necessary to well understand the limitations of the lead acid batteries. Here is a graph of one 100Ah battery where you can show the variation of the real capacity according the intensity drew.


In fact you can get almost 100Ah from this battery only if you draw 5Amp during 20h. As soon you increase the intensity, the real capacity decreases. When drawing 64Amp, the real capacity is only of 64Ah and I suppose when drawing 100Amp the real capacity will be about a maximum of 50Ah with a complete discharge after about only 30 minutes.
The energy wasted in the battery is approximately proportional to the square of the intensity and to don't reduce too quickly the battery life it's necessary to don't draw more than 80% of its capacity. So in fact if at full throttle the intensity is 100A, after 20 minutes you have to stop your electric engine if you don't have a diesel generator.

In fact the batteries alone can drive the electric engine only when manoeuvring the boat or at low speed on a flat sea without wind, waves and current. As soon you request power for a long time you need an hybrid system.

With the hybrid serie configuration it should be better if you have a 48V engine to have a 48V generator to avoid to loose power in the 220V/48V or 110V/48V conversion and to be able to use the total capacity of the generator to drive one or two electric engines; you are not limited by the low power of the chargers if using this inverter system.

I'm not so affirmative than Jean-Paul to say the direct drive pods are more efficient than the inboard drive engines with a belt reduction because slower is the propeller RPM with a bigger propeller, better is its efficiency.
We'll compare that when we'll have the opportunity to sail together in order to compare a Tiki46 equipped with 2 x 10kw electric pod with one another Tiki46 equipped with 2 x 10kw electric inboard engines with a belt reduction and with the 2 x 25hp diesel engines......

Bertrand
Cynthia and Jean-Paul / APATIKI

You've had a year with your electrical drive installation. What do you think of it now? anything you would have changed?
i have a torquedo 2.0 with 4 lead acid batteries that i am using for my 26 foot umiak (light weight skin on frame boat). I use 4 marine, deep cycle, lead acid batteries (due to much lower expense) which are very heavy at nearly 600 pounds. These provide 480 amo hours. The torq is great at moving my very light weight boat. WIll post some video in a couple of weeks. Using the umiak as a test bed for crab claw sail now. The batteries effectively doubled the weight of the boat. I had modified the umiak with ama's to make it into a trimaran, both to get used to multihull sailing, as well as for stability in video work on water, and to get the boat licensed here in WA state, usofa. The torquedo is very effective. Great design. THeir plastic prop is ok, but has suffered some edge chips as it is somewhat fragile. This is an older torq, about 3 years, so maybe the props have been improved. Will look into that. I can get nearly 22 hours of continuous, 40% rate out of the motor, and at maximum thrust am probably moving nearly 8knts. I have a gps now, and will track the various speeds to voltage draw on next outing. But in general, very quality devices.

There are also small, highly efficient diesels that i intended to get and deck mount on what ever wharram i end up with (still looking to buy). These diesels are military grade and intended to only provide source for diesel electrics. THey are marine ready, and hardy to extreme cold weather. ALso known as micro-diesels as they are so small. The one i saw demonstrated would fit into the case of a desktop computer. So my solution is a diesel electric multiple motor approach....once i get the cat. In that system i would go with some minimal battery storage, but would really rely on the diesel for the electric source.
clif

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