Ed- Your questions and many others are more generally addressed on the FAQ page of our website http://electricpadd
Monday, May 10, 2010
Re: [Electric Boats] Introductions.
NiMH Batteries are rated at 10 AH at 24 volts. The motor won't allow more than an 8 AH draw in order to maximize battery durability. Nowadays everyone's talking about Lithium variants. Though NiMH batteries and chargers are not cheap, any Lithium chemistry battery would add hundreds to the cost of the battery/ charger, require more complex waterproof connectors and only shave off 10-15% of the total product weight. Just look at Torqeedo's cost vs power storage and you'll see what I mean. And NiMH is a green choice compared to AGM and NiCad and our smartcharger charges and balances in just three hours. Hybrid car manufacturers use NiMH for a reason.
The 24VDC feeds a high frequency PWM circuit that varies power to the motor based on the throttle knob setting. You can set literally any power level from 0 to 100 watts input using the throttle knob. Knob position is linear with power so 25% setting is 25 watts etc.
We chose 100 watts as the max input power setting because the power out (around 40 real propulsive watts at 4 mph) is roughly equivalent to a couple paddling a canoe. That makes for an efficient boat to match the efficient motor and is just one of many reasons we have a great range with such a lightweight battery .
As you alluded, the correct way to state thrust of any motor for a small boat is to assemble a curve of thrust vs boat speed. We've done this on a hardshell dinghy a canoe, kayak and it's part of characterizing our test tank too. But I'm not ready to release our curves yet. Stay tuned. We can say that on a solo kayak, the Electric Paddle produces a similar 4 mph maximum speed as a 52 lb thrust trolling motor. The thrust required by the kayak hull at this speed is roughly 5 lb (yes- even a large trolling motor drawing hundreds of watts only produces a few lb thrust at higher speeds). At zero mph, the Electric Paddle thrust about half of what we measure from a "30 lb thrust" trolling motor but you don't want to operate the Electric Paddle this way- it's not for a bassboat. The Electric Paddle is designed to operate efficiently at higher speeds as you would see on a portable boat. I look forward to releasing the curves for designers but we're just not ready to do so yet.
Prop is fully described on the FAQ page.http://electricpaddle.com/faq.html .
Cheers, Joe
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