Electric Trolling Motors and Battery.

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Electric Trolling Motors and Battery.

Postby jjam » Fri Aug 26, 2016 3:29 pm

Sold my Daysailer 3 with 4 hp evenrude 4 years ago.The Spindrift Daysailer 1 I just bought came with a 62 lb.electric Trolling motor.It works fine but care must be taken to prevent any metal stainless or otherwise touch both battery terminals.If your stainless shrouds or forestay touch both it will not give you time to remove it before burning in two.My battery box has a full lid and strap and I think that is cheap insurance.
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Re: Electric Trolling Motors and Battery.

Postby GreenLake » Sat Aug 27, 2016 8:07 pm

Always have a battery box with full lid.

I am under the impression that these are are required (in at least some jurisdictions).

Another thing to watch out for is to make sure that the connection to your motor's cables is tight. Or the cable can melt/catch fire. The current is pretty massive, and even a small amount of resistance means that a lot of power is dissipated at the connection.

Curious, what is your top speed? I have a 40# thrust model and can get up to a bit better than 2.5 knots (per GPS) with sails up. (Important to keep sails from flapping, if up, as their drag is higher that way).

Does the 50% more thrust relay to higher speeds?
~ green ~ lake ~ ~
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Re: Electric Trolling Motors and Battery.

Postby Shagbark » Sun Aug 28, 2016 4:49 pm

GL

Are you asking because you are unhappy with the 40#?
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Re: Electric Trolling Motors and Battery.

Postby GreenLake » Tue Aug 30, 2016 12:41 pm

I'm not unhappy with the 40# thrust trolling motor I have. A bit over 2.5 kt is not very fast, which has its good and bad sides. The good side is that I never use the motor if there's wind to sail in. That's definitely a "feature" in my book.

That said, on some occasions I wouldn't have minded a bit higher speed.

My question has more to do with whether the speed I can reach is governed by the thrust, or whether a combination of RPM and propeller pitch is the true limiting factor.
~ green ~ lake ~ ~
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Re: Electric Trolling Motors and Battery.

Postby jjam » Tue Aug 30, 2016 6:53 pm

Untill today I just used the trolling motor to leave and return to the dock.Also I have only sailed this boat three times and this is my first electric motor.
Today we were returning from a very nice sail which started with a south wind and turned into mostly west.And was 15 to 18 .Not really room to tack much so we decided to see how the motor would work.I didn't think to time us but we motored about a mile and a half into a 15 to 18 wind .The sails were down and the wind was on the nose.Most of the time ran full power.I think it took about 40 min.
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Re: Electric Trolling Motors and Battery.

Postby GreenLake » Thu Sep 01, 2016 12:47 am

You must have a pretty beefy battery. I have two smaller (regular ?) ones, and after about 40 min I notice the motor slowing, so it's definitely time to not discharge that battery further.

2.25 (whether in knots or mph) is a respectable speed if the wind really was that strong. I tried to sail upwind in something like 10-12 once and it didn't go too well. (The bow kept being blown off course). However, I tried raising the jib and using the motor to counteract the imbalance in the sail plan (pushing the stern downwind). That curious technique allowed us to tack under jib alone, which meant we didn't have to raise the main and also didn't need to go into full on sailing mode with the boat heeled, crew sitting out, etc.

As we were just doing a short hop from one dock to another (about half mile) that worked out. But ever since, I've been assuming that the 40# doesn't have the power to go against any decent wind. (And then I normally sail, anyway).
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Re: Electric Trolling Motors and Battery.

Postby GreenLake » Thu Sep 01, 2016 12:48 am

Even if you just motor from the dock, if you have a phone or GPS that can give you a speed reading at full power, I would be interested.
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Re: Electric Trolling Motors and Battery.

Postby Shagbark » Thu Sep 01, 2016 7:53 pm

I'm wondering how you connect the battery to the motor. I'm assuming the battery is in the cuddy. If so, you must be running a 11'-12' cable from battery to the motor. How are you connecting that cable to the motor cable? Is the cable running through the cockpit while you sail or do you have a quick disconnect at the motor so you can wind up the cord and stow in cuddy? If quick disconnect, what size because at max 40 amps, it would burn through all but the largest of quick disconnects?
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Re: Electric Trolling Motors and Battery.

Postby GreenLake » Thu Sep 01, 2016 10:17 pm

I use screw terminals found on deep discharge (marine) batteries for that purpose. I used to put the battery that was in use right aft of the CB trunk. That had the downside that it wasn't secured to the boat, but the cables from the motor reached it easily.

With a DS1 I have space in front of the seats. I attach one battery on each side to the seat front (with a strap, in a case). I purchased about 10' of really massive cable. (One or two sizes more up from the wires that come with the motor). I connected one end permanently to the motor cables. For the other end, I got the same kind of eyes as were on the motor cables.

The cable is long enough that it runs from the motor well, along the side of the cockpit (under the side deck - there is an open channel there in the older DS1s) all the way across the boat in front of the CB trunk. In other words, I can reach either battery and just connect it to the screw on terminals. When one battery is done, I move the cable to the other one.

I thought about a permanent installation and cutting the motor cables for a quick connect. I like being able to strip out the weight on days when I don't need the motor - currently I don't bring it more than about 1/5th of the time, although I may be too lazy to remove the batteries :).

Even on trips where I know I will need the motor eventually, I usually do not bother to mount it until its actually needed. It tends to be a bit in the way in the back. Clamping it onto the transom at the motor well is quick and easy and I don't mind undoing and redoing a battery strap and two wingnuts. Normally, I use the motor when I'm becalmed, or before entering a channel with little or unreliable wind. Even when sailing solo, I don't need to bother with heaving to or whatever for the purpose, letting go the sheets and arresting the tiller is about it.

Conversely, once the motor has been mounted, I usually leave it up for the duration. The reason tends to be that the wind has come up and I'm busy sailing. And if I had to use the motor once, chances are, conditions will call for it again at some point during the same trip.

I'm rather fearless when docking under sail or tacking in narrow channels, but I'm also aware that I'm lucky that the local setup isn't that challenging. Calm periods and pockets of calm along a series of connected waterways as well as transiting certain channels and bridges tend to be my primary use case. Although, when it comes to a mid-afternoon calm on open water far from traffic, I "have a nap for that".
~ green ~ lake ~ ~
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Re: Electric Trolling Motors and Battery.

Postby jjam » Mon Sep 05, 2016 6:55 pm

OK today we left the dock with two people in the boat,a new fully charged group 24 battery and calm water behind the breakwater.Across a five mph wind we made 3.8 mph at full power.I didn't think to turn upwind and check but I will.The motor is rated at 695 watts and the battery is 70 amp hours.I guess for my sailing this motor is ok.I would not want to find myself down wind and down tide and need to use it for more than 30 min.The tide range here is 12 to 14 feet so runs pretty fast.
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Re: Electric Trolling Motors and Battery.

Postby GreenLake » Tue Sep 06, 2016 1:49 am

Looks like the top speed that I see is limited by total thrust, then, not some secondary effect like prop pitch vs RPM.

The 3.8 kt that you report are getting close to the point where the power vs. speed curve starts to rise sharply (3.8kt is about 70% of nominal hull speed).

If you go to half power, you will end up somewhat faster than half that speed (because the power curve isn't linear) but the run time will be double.

However, I'm not sure how the numbers add up.

I have an 85Ah group 24 battery and I always assume that I can run my motor for about 40-45min at full power. (I notice that the speed begins to drop at that time). The amp draw should be about 42, so you'd expect it would take 1hr to get to the point where the battery is 50% discharged, but it's really that much sooner because the batteries aren't linear (high amps exhaust them faster).

Also, my batteries are not the youngest any more, so perhaps the numbers would have looked a bit better a few years ago, but as of this year, last trip at which I motored extensively, I thought I could tell some slowdown at about 1.3nm (and was glad that the wind picked up and saved me from having to switch batteries -- I always bring two.

With your motor drawing nearly 60amps, on a 70ah battery, I would expect that you are reaching the half-discharge point a bit earlier than full 30 min.
If you can go 30 min that would be 1.9m (1.6nm), and that is nearly 20% more distance than I get on a 20% larger battery at slower speeds.

But, in my case, I had no wind (glassy surface), but I motored with the sails up, which adds to the drag.

I totally agree with you, electric motors are not a tool to power against wind or tide.

In tidal waters, best you can do is to use such a motor is to get out of (or to the side of) a fast flowing channel, there to await the return of wind (or turn of the tide, or both). If wind builds past what you are set up to handle, be prepared to reef. (Make sure you have reef points and reef lines).
~ green ~ lake ~ ~
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Re: Electric Trolling Motors and Battery.

Postby GreenLake » Tue Sep 06, 2016 1:52 am

A post scriptum: knowing that your motor is limited can be a great impetus in really understanding conditions before setting out, and on working on your skills so that you can get out of most situations under sail. Just saw that point made again somewhere this weekend, forgot what I was reading.
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Re: Electric Trolling Motors and Battery.

Postby jjam » Tue Sep 06, 2016 7:07 am

You may not have noticed my speed was in mph so subtract about half a knot.Very interesting stuff.A friend gave me a second battery so I think I will bring it along untill I get more experience.If you are interested my location is 04649.The summer wind is SW.Thanks for the info.
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Re: Electric Trolling Motors and Battery.

Postby Patriciasailing » Tue Jun 27, 2017 5:11 pm

I am installing a battery for an electric Minn Kota 55# trust 36" shaft. I´ve been reading posts and checking the gallery of pictures, but I cannot find a detailed description of an installation. I am very green in all electrical matters. Could someone please be kind and direct me to the information or share your knowledge?
I would not like to have the wiring just laying about in the cockpit, so I am trying to figure out where I can pass it through. I already installed an inspection port in the middle of the stern floor, (also on my Sunfish) so I don´t mind doing more, but I am unsure of where exactly to install it on the port seat? Or maybe I just need to install the plug on the port seat and with the help of the stern and keel ports guide the cable to the cuddy? Could I just run the wires I read someone installed the wiring inside the port side seat, but no specifics or measurements.
A Minn Kota manual on the internet says I need a circuit breaker (I bought a Minn Kota 60 AMP one), got a 6 gauge wire trolling plug & receptacle adapter, I need to get the MKR-18 Plug & Receptacle according to the plug´s packaging (getting it today if possible).
I really hope I only need one battery because of the added weight, but if you think I really need another one, I will go ahead and plan its installation (or a solar system?). I do sail in heavy winds sometimes, Corpus Christi Bay, Aransas Bay, and I would like to venture further, even go on camping trips, so the power issue would be important. Sorry for such a long post :-) Thank you for your help.
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Re: Electric Trolling Motors and Battery.

Postby Patriciasailing » Tue Jun 27, 2017 5:12 pm

BTW, I have no idea how to connect the breaker....
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