Simple electric kayak

There have been quite a few projects along this line I know, but I think simple ideas usually work better. Here are some guide lines. This kayak has been running for over two years now, and I have been through various set ups. The motor is a Chinese "copy" (but I think out of the same factory) as a Minnkota. Bullet proof. 55lb thrust. You don't have to have this much, but it's advantage is in strong tidal rivers and wind. You'll be doing well to wear out brushes this life time. The aluminium transom is bolted to the flat deck using a matching plate inside the hull, with 8x s/steel 6mm threads separated from the aluminium by neoprene inserts, Silicone to seal.(Spread out the load). The electric motor is separated from the factory twist grip (resistor style controller) and a $23AU chinese 12V PWM rated at 80 amps mounted in the centre console, adjusts speed. Never gets hot. Stealthily silent. The orange Pelican case houses a 100Ah LiFePo4 battery module with a Victron BP-60 battery protect unit. The BP-60 also supports a man over board kill switch system (aux input), so well worth it. Steering is via a suitable nylon rope through four pulleys, which terminate via clasps onto the motor shaft bar. All components plug together (batt, console, motor) with 50 amp soldered Anderson plugs. (Salt water proof). We pack all components in a water proof case on the trailer along with life jackets and seats. The kayak mounts on the trailer bars atop. No solar panels. Battery is fully charged with a cell balancing charger overnight. Battery lasts over seven hours on full throttle. Max speed is just under 10kph. To achieve this you need at least a 4M hull. This one is really a skiff, rated to carry 240kg. It's not a cheap project, but it is compared to general leisure boating. We can launch from anywhere that we can walk to the water. Ideal for Lakes, quiet rivers, and saltwater lagoons. We have had many trips on calm oceans as well. No registration required in Tasmania. Believe me, it's the best use of a plastic sit on kayak that you can think of ! No good for paddling. This matches a Torqeedo and will go much much further. The trouble with a Torqeedo is all your money is spent paying engineers, instead of a good battery. This you can build and repair yourself. The best way always. If this motor ever fails, a new one will cost me $130AU. Why would you spent thousands on something with limited warranty, that you can't repair yourself? Do it yourself..... Grippa.

 

Good work! I am considering the same, where did you pick up the motor?

 

Trolling Motors

E Bay. As far as I can tell they are all the same motors, same factory. Make sure you get the white (salt water use), version, and 3 blades. I have experimented with other props, only to find that the one supplied with the motor is as good as anything. Then you just need to pick a suitable thrust. As I said, 55Lb thrust version isn't too much on my 4M yak. I have also used an 80 Lb thrust on it, but it won't push it any faster (I've hit the hull speed), and it used way more power. (24V version). Find the lowest price you can. Also, this is the controller i use now, way better than the factory one, but no reverse, doesn't worry me because I took off the lock down spring on the motor shaft, so I can hit a log or bottom out with no damage.

http://www.ebay.com.au/itm/10-50V-60A-DC-Motor-Speed-Control-PWM-HHO-RC-Controller-12V-24V-48V-Hot-Sell-/261487620426?pt=LH_DefaultDomain_15&hash=item3ce1e0714a

 

What you could do is a double throw switch and by switching 2 wires around, it should reverse the motor. Your problem will be to find a switch which can handle high currents. Maybe you can extend the two wires and make a little box with high current connectors and swap it in that way. Bert

 

Motor current is 52 Amp so I haven't found a DC double pole double throw switch that can handle it. DC relays are better. You have to be careful not to switch it when in run mode, or invent a system to make it impossible. As I said though, I prefer not to have reverse because I can have the motor shaft unlocked (free to swing up), in case of hitting submerged objects and sand bars. It can really do damage if this happens and you have the motor locked down. You have to understand when you keep the motor shaft unlocked, then there is no point using reverse. Your motor will lift up out of the water. I am very happy to not be so paranoid about hitting the shallows instead of having reverse. it's called compromise. I have a paddle for reverse! I have hit a log at half speed and it's not something you want to do very often. I used the 5 forward 3 reverse switch for 2 years, but they do get hot when on full throttle for too long. Unlike the Pulse Width Modulator, bullet proof, and cheap. Also easier to wire, Pos & Neg in, Pos & Neg out ! Anyone could do it. Thanks for your comments. Grippa.

 

Yes in principle I agree with you not to reverse while the ESC is in run mode, Although I have done it a number of times with the ESC I made myself. The torque is incredible damaging and your system must be able to handle those high torques and the switch must be able to handle the sparking whereby it does not burn the contacts away. The ESC has 3 wires, if 2 of the 3 are disconnected for a fraction of a second, and the ESC is not in full speed and if you know what you are doing, in that case, it can be done. But most of us don't know what the damage will be , due to the torque change and therefore I agree with you that it should be left to the people who are willing to take a chance. Bert

 

My early versions were similar to yours, pushing a 4m inflatable kayak. Some comments based on what I can remember from that version.

1) Instead of the standard boat props suggest trying a sport 10x6P APC model airplane prop. This prop will double your range (or allow half the battery size). It will also increase top speed. I use a 35AH battery without solar panel and found it plenty. However model airplane props are poorer at handling weeds if weeds are an issue.

2) If using the more efficient prop then a 30 lb minnkota is sufficient so cheaper and, more importantly, much lighter than the 55 lb version. It will push my boat to hull speed. Also I use the black "fresh water" version even in salt water without problems so I personally wouldn't spend much extra for a salt water version.

3) I use the chinese PWM controller also without reverse. I've never once missed reverse. Like you, we paddle if going backwards.

4) We also leave the motor free to bounce over rocks and the bottom. I can't count the number of things we've hit without problems (although there can be a good clunk).

I do have a bit of trouble with your math however, you say your 55 lb motor will last seven hours at full throttle on a 100ah battery. Drawing the 52 amps you state for full throttle, it should kill the battery in less than 2 hours. Is there a typo somewhere?

I agree, with a model airplane prop installed, this is a simple, cheap and robust solution that anyone can do. My system total cost was $35 for 30lb motor, $13 for PWM controller, $3 for prop and $40 (EDITops $90---I got my batteries mixed up) for 35AH AGM battery. It can be run at 12v or 24v safely. If I did it again I would spend more for a 35ah Lithium battery since the AGM battery was the heaviest part of the system.

 

Great to chat to someone in Canada doing similar things on the water. The math : I didn't do any. I wanted to carry as much power on board as I could afford, as I use the LiFePo4 pack in my camper as well, so 100 Ah it was. The motor book specifies 52 Amps (it can draw), but it would depend on how much load you are pushing. No load out of water is only 5 Amps. I don't have a DC clamp meter to do an on board check, I just know it will run all day. My daily electrical work is all AC related, with no big DC work involved, so I bought a cheap DC clamp meter online. BIG mistake. Never do that ! I have a Watts Up meter now, it works well, but it's winter here and have yet to try it out in the kayak. Works great in the camper. I'm really interested in measuring what I get out of this battery pack too. I've only run it for one summer, and had no stats off it in the kayak, too busy making videos and having fun.. I tried to measure performance in the bath tub, with the motor fixed to a timber across the bath, but when I reached top speed the water exited the tub !!! Also don't forget that these batteries, the latest Lithium Iron Phosphate type, can discharge to well below your standard lead acid type rates. You can check all that out online. The cost is high, but like I said, motors are cheap, I don't run enough hours to warrant buying a brushless type. Also having a second use like the camper, helps justify the expense. The set up finished in the dry Pelican case with Victron battery monitor & freight here, cost nearly $2000AU plus $200AU for a hand assembled cell balancing charger. The weight however is less than my old 2x 40Ah set up, and goes 3 times as far. That's 3x, although I went from 80Ah to 100Ah. Lead acid are very inefficient. Regarding selection of motor, if load is low, my 55 Lb thrust will only draw marginally more than a 30Lb thrust. When I have to push against wind and river current, then it will draw much more. It's all related to load. There is a much worse scenario, involving hull speed. If you hit hull speed, and keep it there, you will be burning away battery power FAST. In other words, having reserve power, but staying below hull speed is ok, but having a motor that drives well into hull speed, is just a waste of power. Knowing how efficient your hull is at different speeds, helps get the most out of your battery. I know some of the more expensive types like Minnkota have this built in, but I wanted to separate the motor, and went with cheaper versions. I accidentally found out what my top speed was for my hull, when I bought an 80Lb thrust motor. No point in carrying the weight, as I can never use the power. What happens is the wake gets larger, the turbulence from the prop increases, but no more speed, or at least very little more. I will do the math one day maybe, when I have the stats this summer I will post in this forum. Grippa.

 

To Junior member >> You said your early versions were 4M inflatable. What did you end up with ? Grippa.

 

Grippa...are you talking to yourself or me? LOL

Actually I don't understand your question. I'm still using the inflatable kayak if that is what you mean.

You can't measure performance in your bath tub...the prop loading is completely different than cruising on a boat. So you didn't lose anything with it not working out.

How heavy is your Pelican case package when full of batteries and stuff? Lithium is a good choice if one can afford it. Alternatively AGM batteries, especially good scooter ones, will also significantly outperform standard flooded lead acid.

Since speed is proportional to the cube of the power, slowing down (a little) will increase your range (a lot). Conversely adding a lot more power increases speed a little, even less if pushing hull speed.

 

Sorry, I didn't realise your name was ElectricKayak ! and I don't do much on forums generally. Also I don't know how I came up as a Junior Member ! Good point..... I'm 55 YO. ok so you are using an inflatable. Yes you are right, prop loading in a bath is probably different, I was just trying to measure Amps. It did show me though that these things are not toys, they push a serious amount of water. The reason I know it's not drawing 52 amps all the time on full throttle, is because the battery pack lasts too long. Backwards but still information. It will help when I get it out there with the Watts Up meter. I bought that because it is nice and compact. There is a way to hook them up with just one wire measuring, not pos & neg. It keeps the heat down.

My 100Ah lithium case weighs 17kg. My 2x AGMs totaling 80Ah weighed 26kg. Don't get mixed up with the early lithiums. This is LiFePo, a bit heavier, but much safer. The difference between old & new packs is a one arm job or a two arm job. I went with AGMs (one at first) because it was just an experiment. Then we found out how much fun it was, and how far we could explore, so things got serious. I had this dream in my head for a long time though I think. The two AGMs are now my fridge camper batteries. They charge easily off my alternator and solar panel, and don't have to be balanced. I still call them lead acid, but yes, I know they are a bit better specification.

I'm prepared to travel at full throttle, because we use our kayak for scenic river cruising, small rivers, sometimes sections between water falls or shallow sections. These areas are impossible to get to with larger craft, and you can be guaranteed of a peaceful day. It's good to cover a reasonable distance, after the effort has been made to get there with the kayak. So I know I could save power, going slower, but some compromises have to be made if we are to explore further. I drew the line with speed when I realised a bigger motor (80Lb thrust) chewed the power on full thrust, with no gain at all in speed. I guess everyone's needs are different. We have travelled 10km up rivers and back, with no problems, and plan to go further. Sometimes other family members come along and it gets three outings with three crews.

If any members out there can recommend a light and more efficient hull, I am very interested.

 

Curious what speeds do you normally cruise at? And what is the top speed?

 

Again, no reliable data, my GPS only works on roads and doesn't measure that low, or not well anyway. I am going to try a program on my smartphone this year. I know there are products you can buy especially for this, but it's never going to get used again. We know how far we've been up river or across bays by checking on maps. We had someone jogging by a riverbank once, and we left him behind. So I'm thinking close to 10kph or approx 5 knots. We cruise at top speed unless there are obstacles or something to check out more closely. Can you post videos on this site ? I have one on Google drive.

 

Kayak video (on the water)

 

http://youtu.be/sd5o3i4kJFQ