Im presently working through some of these same
calculations for my 23 launch which I hope to launch at the
end of the summer after 4 years of construction. The
propulsion system is the last major item on the list. The
weights, speeds and 36V propulsion system for my launch
are similar to those described here. My calculations
have, unfortunately, led me to question the suitability
of golf cart components for a boat of this size. Id
love to find out Im wrong!<br><br>At 36V each hp.
consumes 20.8A. You dont want to discharge the batteries
below 70% for risk of damaging them. A good 6V battery
may be rated at 145 amp hours. That leaves roughly
100AH useable. If the boat in question can actually
make 5mph with only 2 hp (this must be close to hull
speed; it would be for my boat) the range is only 2.4
hrs. or 12 mi.<br><br>If the system is built around 6V
golf cart components, adding to the range would
require an addition of 6 more batteries to keep the 36V
multiple. On my boat there isnt a prayer for finding room
for 12 batteries.<br><br>Im currently planning on
using 6 12V batteries that are rated at 115AH. This
gives me total capacity of 5.8 hrs at 2hp. Im thinking
this may not be adequate simply because I dont know
how much power my hull (a fantail launch similar to
the Elcos) will require in various conditions. In a
pinch I could squeeze in 3 more batteries to get a 345
AH bank.<br><br>As I said, Ive yet to do my system
(although its looming on the near horizon) and I would
love to discover Ive overestimated the needs. As it
is, though, I fear that 36V/145AH to push a 22, 1500
lbs boat is going to yield a disappointingly
restricted range.
