: Easier and alot cheaper to use a standard electric trolling motor (for
: fishing) and a small car battery. With the drag of a kayak, battery should
: last nearly forever.

I've done that on an inflatable boat. Car batteries (particularly the well-used ones which are readily available for such games) don't have a very long life when used to drive trolling motors. They are great for high current for the few seconds needed when starting a car, but they just aren't meant for really deep discharge and heavy use.

Fortunately, batteries designed for deep-discharge are just as easily available at Wal-marts and Sears stores. Look for liquid filled batteries designed for golf carts (roughly the same size and pretty close in price to a car battery) or gel-filled batteries for electric wheel chairs. These cost more but won't leak if they get turned on their side.

My 17-pound thrust trolling motor drained a (not too perfect) car battery after about 2 hours of use. The voltage dropped down to the point where it was not doing much. I would expect double that performance, or better, from a new deep-cycle battery. This design has a 36 pound thrust trolling battery. That is about a one horsepower motor. One horsepower is just under 750 watts, so this should draw about 60 to 70 amps from the battery each hour at top speed. A battery rated at 210 amp hours would last about 3 hours at that draw. at half speed you might get 5 to 7 hours of use from the thing. They sell in the $60 range most of the year, but come on sale occasionally. Want more use--buy a bigger battery, or put in two.

a 36 pound thrust motor may be oversized for this application. The motors used on electric bicycles and scooters are in the range of 150 to 200 watts. You could probably get maximum hull speed froma much smaller motor which would drain the battery less.

I noticed the device comes with a wall charger. I can see where it would need one. Those solar panels look like the 5 watt panels sold by Harbor Freight. (part number 41144) I can't tell if they have two or three of those panels mounted. But let us suppose that you'll buy 4 of these, 'cause right now they are on sale for $40 instead of the usual $50. In full sun you'd get 20 watts going back into the battery for every hour you had good daylight.

For every hour of full-bore use (750 watts) you'd need to charge the battery for 37 1/2 hours. That is about 3 days of charging for each hour at maximum speed. If a slower speed only used 100 watts, you'd need 5 hours of charging for each hour under power.

Put more money into the solar panels (at maybe $6 a watt) (look at http://www.wholesalesolar.com/index.html for instance) and you could easily get larger, and more economical panels. Lets say you bought a panel which produced 100 watts every hour, and used an efficient trolling motor. You could probably propel a kayak continuously with such a setup.

And on the overcast days you could put up a sail.

PGJ