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post #61 of 85 Old 12-27-2015
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Re: Installing an electric motor

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Connect two of these puppies in series and you are good to go for your charging:
Turnigy 1080W 220~240V Power Supply (13.8V~18V - 60amp)
Search under RC chargers for other sources. An RC charger is about the cheapest source to get the kind of power you are looking for.
Um... No.

A reasonable energy usage of a 40' sailboat at cruising speed is roughly 13.5hp or about 11.1kw. To convert this to 12v battery power you would need 11 of these toys. But this is just cruising speeds, no head wind, no chop, no problems. And fla batteries do not accept bulk charging rates at a high enough C to handle this massive influx of power. So either the battery bank has to be massive, or you need to swap to some other chemistry.

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post #62 of 85 Old 12-28-2015
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Re: Installing an electric motor

um, i was only supporting his choice of generators and matching his voltage and rating. Two in series would be 36 volts, which is what his motor runs on. I was not making commentary on the over all power to push his boat.

BTY: I'm not sure your calculation is completely accurate on how much power to push his boat at a reasonable speed. I don't believe you would need to hit full hull speed to be practical. If you can hold 4 knots into a 30 mph headwind, you have enough power. On days with no wind, that would likely add 2 knots or more - fast enough to be practical.

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post #63 of 85 Old 12-28-2015
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Re: Installing an electric motor

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Originally Posted by Daveinet View Post
um, i was only supporting his choice of generators and matching his voltage and rating. Two in series would be 36 volts, which is what his motor runs on. I was not making commentary on the over all power to push his boat.

BTY: I'm not sure your calculation is completely accurate on how much power to push his boat at a reasonable speed. I don't believe you would need to hit full hull speed to be practical. If you can hold 4 knots into a 30 mph headwind, you have enough power. On days with no wind, that would likely add 2 knots or more - fast enough to be practical.
I do not believe the hobby grade Hobby King power supplies are meant or designed to be run in series. Some lab grade supplies can be run in series, they are specifically built & wired for this, but cheap ones often can not. At the worst, depending upon internal AC/DC wiring, you could create a short and kill one or both of the power supplies.

I have had some awful junk from Hobby King and also some egregious knock offs that don't do what the real branded product will. I bought two Junsi Cell Log 8S units that were not Junsi nor were they the 8S data logging model. I bought a few LiPo batteries and the cells were not even close to being matched for capacity, or impedance, nor did a few of the cells hit their mAh rating. You need to be real careful with Hobby King and know exactly what you are getting. I really don't think I'd want to depend upon a Hobby King charger to keep my expensive vessel batteries charged. These are short intermittent-duty products for charging small 4-10Ah LiPo, LFP or NiMh batteries.

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Last edited by Maine Sail; 12-28-2015 at 06:02 PM.
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post #64 of 85 Old 12-28-2015
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Re: Installing an electric motor

I had no specific experience with that brand. To run those in series, you may have to lift the ground, and/or isolate the case. Switching supply should be isolated from the AC line by the transformer.

One comment I would say about running any EP setup. One should have extra cables on hand at all times to bypass the motor control. If for some reason the smoke escapes from the controller, you don't want to be stranded. You also don't want to be stuck running full speed. You should have enough wire on hand to run the batteries in any kind of series/parallel combination, so that you can approximate the speed you need.

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post #65 of 85 Old 12-29-2015
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Re: Installing an electric motor

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Originally Posted by Daveinet View Post

One comment I would say about running any EP setup. One should have extra cables on hand at all times to bypass the motor control. If for some reason the smoke escapes from the controller, you don't want to be stranded. You also don't want to be stuck running full speed. You should have enough wire on hand to run the batteries in any kind of series/parallel combination, so that you can approximate the speed you need.
This would work for motors like my LEMCO brushed motor. Indeed some boats used contact switches to provide power to the motor. I'm not sure if newer AC phased motors would allow for jumper cables as a backup though. But, it is a feature that is available to get one moving should controller electronics fail on brushed motors. Though after eight years I can say my EP system has been pretty trouble free and have never had to go to any backup plan.

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post #66 of 85 Old 04-08-2016
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Re: Installing an electric motor

Has anybody been following on youtube Sailing Uma and their DIY electric motor installation ?
I found their project interesting and well thought.
Any comment ?
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post #67 of 85 Old 04-08-2016
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Re: Installing an electric motor

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@hellsop is correct, the boat never had a inboard. It was never designed to have one. My thought on this idea was to have solar panels to charge the batteries to run the motor. But again, its just an idea. I have a 8hp outboard to use and I'm guessing that if I ever go any distance, that it will suffice. I'm not trying to circle the globe. but maybe a trip from Texas to the Keys one day.
I know the Torqueedo is supposed to be a very nice set up. I believe there are other electric outboards (other than trolling motors) but the Torqueedo seems to have a very nice system including charger/battery and what not. They seem expesive, but when you factor in all that has to be done to make one from scratch they really start looking like a bargain.

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post #68 of 85 Old 04-10-2016
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Re: Installing an electric motor

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Originally Posted by wavestimulus View Post
Has anybody been following on youtube Sailing Uma and their DIY electric motor installation ?
I found their project interesting and well thought.
Any comment ?
They're whole project on the boat is pretty cool. At least they seem to be having fun. Their EP install, they took the long way around the barn trying to use a fork lift motor thinking it could be bolted up to their old ICE transmission. They should have just bought a packaged DIY kit from one of the EP vendors out there, in my opinion. Don't know if they've posted any recent adventures.

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I think in their case, it was.

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post #69 of 85 Old 04-11-2016
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Re: Installing an electric motor

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Originally Posted by Daveinet View Post
um, i was only supporting his choice of generators and matching his voltage and rating. Two in series would be 36 volts, which is what his motor runs on. I was not making commentary on the over all power to push his boat.

BTY: I'm not sure your calculation is completely accurate on how much power to push his boat at a reasonable speed. I don't believe you would need to hit full hull speed to be practical. If you can hold 4 knots into a 30 mph headwind, you have enough power. On days with no wind, that would likely add 2 knots or more - fast enough to be practical.
Something to remember is that speed vs power is a curve, it's not linear. After about 3 kts it starts getting steep quickly. You might be able to push a boat at 3kts with as little as 1kW, but to get to 6kts might take 10x that or more, depending on the boat's LWL, hull shape, hull cleanliness, etc. Hydrodynamics are a *****.
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post #70 of 85 Old 04-11-2016
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Re: Installing an electric motor

I looked at a Thoosa system (briefly), the run time at WOT is one hour for my boat based on the 48v batteries that they recommend. That just wasn't going to work for me.

Just broad reachin' through life...
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