batteries in about an hour instead of half a day of
connecting and disconnecting batteries from a single-cell
Another issue related to power is knowing when
you're empty. Check out HobbyKing or Tower Hobbies for
low voltage fingernail-sized alarm modules that sound off
when battery voltage falls below a preset value. The best
systems monitor the individual cells in the battery and
sound an alarm when any of the three cells fall below
critical voltage. Photo 3 shows one such system,
available from HobbyKing ($3). Finally, although it might
seem like a trivial matter, install plastic extenders on the Li-Po battery JST connectors, as in Photo 4. The extenders —
which sell for about five cents each — will save your
batteries from premature failure. Whenever you charge a
Li-Po in a smart charger, you have to plug in the JST
connector. Tugging on the wires to remove the plug is
inevitable, and this will inevitably ruin the plug.
provide anywhere near the theoretical 1,000 x 11.1 or
11,100 rpm at full throttle. Plus, the KV value will
decrease as wear accumulates from improperly balanced
propellers, impact, and the accumulation of dust and grit.
Li-Po batteries also deteriorate with time and use.
Track the internal resistance and pull a battery from
service as soon as you notice a significant deviation
from normal. You don't want a cell to fail in flight.
At this point, take some pictures. If you've ever built
and flown model rockets, planes, or copters, you know
that the Elev- 8 is going to show wear and tear, even if you
manage to avoid an outright crash. Of course, your
pictures should include more than simple camera shots.
Include a “snapshot” of exactly where you're starting
from, in terms of motor efficiency, battery output, and
overall mechanical integrity.
Create a logbook and catalog the actual KV,
maximum rpm, and power draw from each of the four
ESC motor circuits. You can expect these values to decay
with normal wear and tear and the inevitable crashes.
Fortunately, there is a variety of affordable meters on the
market, starting with dedicated KV and rpm meters ($20,
HobbyKing). For about twice that price, you can get a
meter that also measures watts, battery internal
resistance, and temperature, and that doubles as a servo
tester. As you might expect, the 1,000 KV motors don't
One of the best features of the Elev- 8 is ease of
maintenance. Given time and a workspace, everything is
field-replaceable. With the Parallax Crash Kit, you're
covered for motor mounts, motor parts, and props. You
could even carry a spare aluminum tube, pre-drilled to
accept the 4-40 mounting hardware.
As with a real copter, you should have and use a preflight checklist that includes battery check, prop collet
check, transmitter battery check, and failsafe setting
check. You'll also want to note the wind and weather
forecast before you head out to the flight field.
The Fun Part
PHOTO 4. JST connector without (left) and with (right) protective sleeve.
Recommended inexpensive insurance against JST connector failure from
unplugging the connector by the wires.
Up to this point, it might seem
like owning and maintaining a
quadcopter is like owning a sailboat
or an old house. You're always fixing
something. However, that can be
enjoyable. Of course, the real fun is
experimenting with the craft. For
example, on my to-do list is to work
with the optional ultrasonic range
finder and modify the flight
computer so that instead of simply
hovering at a given distance from
the ground, the quadcopter takes
72 SERVO 10.2012