Welcome to the Dark Side!
First I think you would want to double the capacity of your battery bank.
The e-bike battery does make a good docking reserve. I have three 20ah 48v packs and if you stay under 5 amps they actually give you some meaningful range. In fact, if you could be satisfied with using your electric drive only for docking, a pair of them and a 6a charger would be all the battery you need. But for four hours or so, you should plan on having a substantial bank and I don't think you will be perfectly satisfied with only 100ah.
The 5kw motor is an acceptable match for your boat. However, if you run a 5kw motor at a certain boat speed and run a 12kw motor at the same speed, the 12kw motor uses about the same amount of power as the 5kw motor. The advantage of the bigger motor is of course higher top end power and also it can disappate heat more effectively, The motor will last longer and stand up to more abuse. There is very little overhead in simply turning the motor, unlike the case of two different size diesels. So you might consider a ME0913 or similar. Costs a couple hundred $ more is all. Same shaft size and mounting face/holes. However, the 5kw motor WILL WORK, as long as you don't ever need a burst of higher power. 5kw is about 6.3hp, if you don't mind an apples vs oranges comparison.
Brushed motors cannot be used when propane or gasoline accessories are aboard. If you keep a gasoline outboard as backup, for instance, or a propane cook stove or heater. If you can do without stuff like that, a brushed motor does have some advantages. In an emergency you can for instance run straight off the batteries, or off some of them, if the controller malfunctions. The controller is cheaper and you can get a suitable Chinese PWM controller on ebay for about $50 and be able to afford a backup.
BLDC controllers are not all alike. The Kelly controllers can be configured with a windows computer (sadly there is no Linux version of the software and I only use Ubuntu) and an ordinary USB to Serial adapter using the free software from their site. Some of the newer ones can be configured with an Android tablet. If you tell Fany at Kelly when you order a controller they can preconfigure specifically for the motor that you specify and the operating parameters required.
Be sure that the controller is rated for the highest sustained current you anticipate running. They are usually rated nominally at their peak power, which might be the max the controller can stand for one minute or some such unrealisticism. One or two steps up in power adds to cost, but does not (for a given output power) consume appreciably more power itself, and since the controller will just be loafing along, cooling is not as critical. In fact you can often just rely on passive cooling, using an aluminum mounting plate as a heat sink. Especially for the Kelly controllers with the ribbed aluminum cases. And as with the motor, the bigger controller gives you higher top end power.
How big is your prop, and what pitch? It is quite possible that the existing gear ratio will work nicely. If not, perhaps you could reprop, or have the existing prop cut down a little. I do hate the idea of making a prop smaller just on principle, since typically a larger slower prop will be more efficient, but it could be an option if you are stuck with too low of a reduction ratio. If your prop is lets say a 12x10 3 blade or smaller you should be just fine with 2.2:1 I think. Even about 14x10 will work okayish... I currently have 2:1 with (usually) a ME0201014201 5kw brushless motor and a 14x10 3 blade and neither motor nor controller have ever got too hot to leave my hand on. I also have an ME0913 and I have used both. My bank is flooded cell lead acid 6v golf cart batteries, 8 of them in series for 48v nominal and 225ah capacity, in a 27' former sailboat, just to give you some point of reference. I do think I would be better off at 3:1 and I will try a new gearbox when I get home, but 2:1 does work with no issues.
One nice thing about a bigger bank is if you don't need the juice for propulsion, you have a lot of house power for running electrical appliances. Air conditioner? Sure, for a while. Refrigerator for your beer? Of course. Espresso machine, blender, microwave, all good within reason, as long as you don't need all that electricity for pushing the boat that day.
I currently get by with only shore power charging but I will soon be constructing a solar canopy to cover the entire boat, to give me shade as well as to generate plenty of charging power. Consider at least mounting a couple hundred watts of solar panels on the pushpit rail. Twice that much if you can. It will extend your range considerably, on sunny days. 200 watts is a peak current of about 4 amps, enough to ghost along at low speed without depleting the batteries, assuming a sunny day and a good angle to the sun. Sure, you only can have perfect solar conditions a few hours a day but even so, it is worthwhile.
There is really no reason to use mechanical reversing, unless the motor's internal cooling fan is inadequate in the reverse direction. Nor is a "Neutral" needed. There is no minimum idle speed... you can approach a dock at 20RPM if you like. Electrical reversing works nicely. I have in my two (I have a backup, of course!) controllers Kelly's "stick shift" firmware. A single potentiometer handles both reversing and throttle. I have just a simple $1 potentiometer fiberglassed to my tiller, and it is very convenient to hold tiller in one hand which also controls direction and speed, freeing the other hand for beer.
I recommend using terminal strips for all the connections, instead of those cheesy multi circuit plug connectors. I had nothing but trouble with them. The wiring is more complex than you might assume. Lots of connections to shake loose and cause the motor to go bananas.
Don't forget spare fuses! My controllers use a 10a ceramic fuse of a physical size that is not common in chandleries, auto parts stores, etc, and also there is a 300a main power fuse.
Instrumentation for these kits is to me, inadequate. Get a cheap combination digital meter that reads current to 100a, and voltage to 100v. Connect the current shunt between the negative battery terminal and the controller. Get a cheap Hall effect digital tachometer, too. Or maybe not... come to think of it you won't have access to the prop shaft. I do wish Kelly had a speed output on their controllers. Maybe you could engineer something with an inductive pickup on a phase cable, and a microcontroller counter and display. You might also be able to acoustically count prop beats. Or use the motors hall effect sensor signal to drive a counter.
Use the heaviest cable that you can realistically use. I use 2/0 welding cable for battery cables and phase cables. It keeps line losses small and relatively insignificant.
---In electricboats@yahoogroups.com, <jesper@...> wrote :
Thank you for letting me join this group. It seems this is the place to go for good information.
I am designing the electrification of my sailboat, and I would love to hear what you guys think about it.
I have thought this out, only based on internet research, so some input from people who has really done this would be very welcome.
The boat is a Nordship 808, a 27 foot quite light sailboat. It has a finn-keel and a Volvo Saildrive with a Volvo Penta MD7B. The MD7B is 17 HP and way too much for the boat. They came with 8 hp from the yard when they were built, but his one has a much larger engine for some reason.
You can see data on the boat here:
NORDSHIP 808 Sailboat details on sailboatdata.com (units Metric)
Be aware that the numbers are metric in this link.
I do not motor a lot, last season I used only 5 gallons of fuel. The reason for the conversion is:
- The diesel engine might not have many years left (1984 raw water cooled)
- Much less maintenance
- No diesel smell and hot engine in the cabin on hot summer days
My goal in terms of performance and range:
- A little hour of hull speed (5.6 knots)
- 4 hours of 4 knots
I live in an area with nu current and tide to speak of, and quite sheltered waters too.
This is a link to my endavours last year to give you an idea:
The site is in danish, so click the button labelled "Luk" to close the image view and see the map :-)
This is what I have in mind:
Motor and controller:
The 5KW kit from thunderstruck
http://www.thunderstruck-ev.com/sevcon-brushless-sailboat-kit-8.5kw.html
As an alternative to this, I have come across this kit, which I like because it has a controller that can be programmed without paying a surcharge for software, but is it as good as the one above? What I like about the thunderstruck package is that all the cables are included and they have a nice video showing how to install it.
Motor-Controller Combo - Alltrax SR48300 & Motenergy ME0708 36 or 48 VDC Kit | eBay
Propulsion:
Coupled to the existing Volvo Saildrive wich has a 2.2:1 reduction. The mount and copuling is done by a mechanical engineer, and we are aware the no axial load can be put on the motor. This is no problem.
The prop is quite large (since the 17HP diesel) so I hope this will fit the electric good. (Thougts on this?)
The saildrive has reverse and I will use that. For throttle I will use the existing lever (which also controls the reverse on the saildrive), connected with the throttle-cable to a 0-5 KW potmeter with a lever arm.
Batteries:
What I have in mind here is a bank consisting of 16 CALB-100AH prismatic cells, which should give roughtly up to 100 AH at 48 volts. Of course with BMS and an appropriate charger. How does this sound related to my range goal?
In addition I will mount a 48V electric bike battery of 20 AH, which can be coupled in as a reserve for docking, if the main bank fails, or is somehow depleted. (I know this kind of battery will only deliver about 20 Amps continous, but it is only for harbour manouvers, nothing else)
Example of such a pack (I have read, I think on this forum, about a forumite who tested such a battery pack with success (for emergency purposes)
http://www.ebay.com.au/itm/48v-20ah-LiFePO4-Batteries-5A-Charger-BMS-Electronics-Rechargeable-Powerful-Air/142232669149?rt=nc&_soffid=5025313206&_soffType=OrderSubTotalOffer&_trksid=p5731.m3795
Charging:
Shore-power: 99 percent of my trips have overnights in a marina.
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