Alex M wrote: ↑
Dec 16, 2017 9:07 pm
Thanks, Justin. 95% DC-DC is impressive, didn't know this was possible, most converters are under 75% efficiency.
Normally it's more like 80-90%, not 75%, but in any case that's because most converters would have their components cost optimized for the current & power level required using the inductors and mosfets at the edge of their designed operating area. If you optimize the design for max efficiency with minimal losses, then you end up with much less current through the power electronics and magnetics than what they can handle, so you spend more and have a larger/bulkier package for the power output. It's not that difficult to make a DC-DC with high efficiency, it's just not very economical when people are comparing specs / $$.
Yes, 200W output is below 400W of that Torqy 403.
If your goal is powering a kayak though, you might be surprised at how pointless it is to even put 400 watts of power into the engine. You can pretty effectively get up to hull speed with like 200 watts in an efficient boat hull like this, and the incremental gains in speed make it fairly pointless to drive the power much higher. You end up with like another 0.5 kph in your speed and cut your range in half.
I was playing around last weekend in my rowing wherry with an RC plane propeller powered from an electric skateboard hub motor on a long shaft, it was crazy how well you can cruise from even 70-100 watts of power, and how little each additional 100 watts added after that.
Yes, ebay and ali-express batteries are toss a coin.
I was referring more to their dc-dc converters than batteries, but yeah the same thing generally applies across the board! For the DC-DC's, as a rule divide their claimed current output by 2 or 3 to get a reasonable continuous amps rating (at least that's what we found on half a dozen various samples).
In any case I'll be curious which way you go and how this all pans out with the Torqueedo unit. There really is a dearth of good options for electric boat assist in this power range. It's all either lame trolling motors or large outboard replacements. The other option that I've liked the look of is electricpaddle
Even though it's a 24V battery system that they offer, their motor controller works just fine with 36V and 48V packs, if my memory is correct from when we chatted with them at the port townsend boat festival.
Big Dummy Frame (yes This One
, thanks ES!) with prototype 26" Grin all-axle front hub, Phaserunner controller, and 52V 11Ah Cellman triangle pack
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