Re: [electricboats] Redwing 18 electric repower

Bill,

Good luck with the conversion!

I have played with both a Torqeedo 2R and a Torqeedo 4R on a Catalina 22 sailboat.

With AGM batteries - the Peukert effect is a SIGNIFICANT consideration.  The less you draw from the batteries at a time, the longer the run time you'll get.

Like you, I appreciated the 24V setup.  With the same 4 batteries, I could run two banks of 24 volts instead of one bank of 48V.  What I liked about that was the ability to use one bank, and hold the second bank in reserve "in case something bad happened" (i.e. if the primary battery ran out faster than expected).

That having been said - once you have confidence in your abilities and discipline, if you combine the batteries together in parallel, the current drain per battery will be lower, resulting in a longer run time.

I'm currently working on a different wooden boat about 13' long, with a Torqeedo 4R.  The nice thing about the 48V system is that I can use eBike batteries, which are MUCH simpler and easier to buy and use.  I have a larger battery for the main battery, and a smaller one for "backup".

I haven't had the time to run many experiments yet - but so far, really like the eBike batteries!!  Unfortunately, I haven't seen them in 24V packages.

Again,

Best of luck with your experiments!!

John

On Wednesday, November 25, 2020, 10:25:46 AM CST, wdr99 via groups.io <wdr99=yahoo.com@groups.io> wrote:

I posted this over on the wooden boat forum but I'm not sure how much overlap there is from this group.  Thanks to all who have posted on here and to those who have answered my questions.  

After one season with my Redwing 18, I've decided to repower with electric. Out goes my Honda 20, in goes a Torqeedo Cruise 2rs.

 

Why am I doing such a thing? Here's my list: the chance to tinker, the thrill of the chase (lots of incremental improvements open up), no gas, no gas tank or fuel gauge, no tach, no more shifter and throttle cable, less noise and vibration, no grease and oil, no more 140lb behemoth, aka the usual reasons one chooses for going electric.

 

No turning back now, yesterday with the help of my homemade gantry, chain hoist, and my father-in-law I yanked out the 20hp, holy moly is that thing a beast and I won't miss it!

 

The Redwing is a displacement hull and pushing her past 6.5 mph took everything the Honda 20 could do. Admittedly, the Honda had completely the wrong prop, a 10 inch pitch which is designed to push a boat up to 20 mph or so. But the bottom line is that a 6hp equivalent is plenty for what I'm trying to accomplish on the water.

 

I had originally planned on going with an 80lb trolling motor and I did purchase the critical pieces aka a shaft, motor and controller from Minnkota's parts window. But circumstances have directed me to the Torqeedo with the Minnkota as a redundant power source.

 

I chose the Torqeedo 2 vs the 4 because of the smaller 24v source which I currently had 70ah of AGMs. Eventually I can increase battery capacity, install maybe 200w of solar, migrate to lithium, and perhaps get a generator.

 

Assuming a top speed of 6.2, my estimated performance assuming Peukert effect and 80% DOD allows 2.5 hours of propulsion at 3.6 mph. My wife and typically motor around for 2.5 hours so right out of the box I'm assuming a 9 mile afternoon on the water, that's just fine for us.

 

If I install 200w solar, I estimate motoring around at 2.9 mph all day on solar alone.

 

Eventually, if I upgraded to 140ah of lithium batteries with 80% DOD, I estimate I can motor around for 5 mph for 2.5 hours, that's pretty much exactly right for us.

 

I'm being pretty conservative on my numbers, based on evidence I've gathered. We'll see in 6-7 months, once the water is open again, if I'm anywhere in the ballpark. I'm also taking the winter to redo the cockpit for more floor space (less storage) and finish the cabin.

Bill