DIY EV kayak discussion on your solution to get more run time with easy to find parts

Electric kayak forums have been around for years. Off the shelf products have caught up to the point that real solutions are getting easy to find and use to now see performance like 80 to 100 miles on one charge. I am seeing kayak forums that are scattered with different groups from fishermen, day tours, photo trips where now kayakers are looking to do other things with their hands besides paddling. I am working to get a simple trolling motor to propel a kayak farther than 10 to 20 miles with a deep cycle battery that many are using today. With only a few changes I think that many now can keep the kayak they have and now get many more usable miles to get more out of a day trip than what one could hope for.

I want to share and discover what you have come up with to make kayaking even more fun for everyone instead of just the few athletes who are the main group who is enjoying this hobby today. I am painting this topic with a wide brush, but I think the idea is sound.

I have seem factory electric kayaks that offer a few extra miles in run time and big costs, I don't feel it needs to be this way.

What have you built?

Gary

 

this is a DIY wood kayak kit that uses a trolling motor.

I was looking for a kayak that can be used and operated with out hands. I found a fisherman who came up with a kit and plans for just a kayak. I will post a photo of it on my truck. What I like is that you control it with your feet. Forward, reverse, and left and right. This leaves the hands free to fish or take pictures.

I want to talk about the power part of this boat. I am using a Minn Kota 40# thrust motor and these are low in cost used or new if you want from Walmart and such. I put a deep cycle battery in and went out for a day of fun. My GPS tracking app on my smart phone showed I was able to get a bit more than 5 mph. This was good for me and my 10' kayak. What I found out however was that my run time was from 2 to 6 hours depending on what speed I wanted to use like 3 mph all the time or 5 mph for a shorter time.

I wanted more distance and did the search, I could only find that others were looking to find props to get a little more speed, but nothing but bits of info to get more distance. Well maybe I have it now and I want to share.

Talking with Jim, the man who built the kit, I asked what can we do to get more. Changing the battery from Lead Acid to LiFepo4 was a great start. For our tests we used 5 cells at 100ah to get a 17v battery. The controller is custom made to control the motor and inputs for using the feet. The controller was modified to handle the larger voltages and currents and the test results are in on the first run. Here is that report.

Well the new batt just ran out of gas. The voltage dropped to LVD after 25.5 hours of run time. The battery current was a constant 3.1 amps which results in 10 amps thru the motor. That motor current translated to a speed of 3.5 mph. So if you multiply the run time by the speed, you get a range of 25.5hrs x 3.5mph = 89**miles*a bit further than the 20-25 mi we get with a grp 24 (75AH) LA battery. The energy used is 3.1 A x 25.5 hrs = 79 AH from the battery.*

Where is the rest of the 100 AH from the battery? I charged the batt to 3.55 v/cell or 17.75 volts. *That is a little less *than fully charged. Throw in another 10% for the measurement tools, and used batteries you can end up with 80 AH capacity.*

What about faster speeds? 20 amps of motor current required 12A of battery current. 30 amps of motor current takes 23 amps of battery current. And 40A motor uses 30 battery amps. *Previous tests indicate 20 amps of motor current provides a speed ot 4.2 mph while drawing 12 amps of current from the battery. So *if the AH available is 80 ah, then the range at 4.2 mph will be 80ah/12a x 4.2 mph = 28 miles. * *AND *for 30 motor amps you can expect 80/23 x 4.5 = 15.5 miles, and for 40 motor amps you can go 80/30 x 5.2 = 12.5 miles...

This report is just our notes and we can speak more about that. But to get 89 miles at 25.5 hours might be more than you want to do. But this means while camping one can get three days of real use without recharging. Nice.

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