Q-82: I just purchased an FMA Direct/Kokam Li-Poly battery pack. It
only has two wires coming out of the pack. Do I assume one is for charging and
the other for operating my electric motor (discharging)?
A-82: When I first read this E-mail, I thought someone was pulling my
leg. I mentioned this note to several fellow club members when I got to the
flying field later that same day. Surprisingly, I didn’t get a “funny” reaction.
One member indicated that he owns a new Hobbico ElectriFly Li-Poly battery pack
and that it has two sets of wires (a total of four) exiting the pack; one pair
goes to your ESC and motor, and the other pair of leads is for charging only.
That charging cable is routed through a special protection or safety device that
is built inside the battery pack.
After hearing this, I contacted the reader who had sent the original E-mail. He
explained that the first Li-Poly battery pack he purchased was the ElectriFly
and that it indeed had two pairs of wires exiting the pack.
Then he purchased that FMA Direct /Kokam pack (www.fmadirect.com), and it only
had one pair of wires (a red and a black) exiting the case. Since he was already
using separate cables to charge and operate his motor, this new pack had
confused him. Then I understood and was no longer laughing.
Hobbico has evidently addressed the safety aspects of charging Li-Poly batteries
with this new “built-in” device. You can obtain the same feature by adding an
FMA/Kokam Safety Guard external to the pack. The mystery of the four-wire
battery pack is solved.