BTW the battery clearly specified "NiMH". The instructions also said to
discharge it completely before charging; correct me if I'm wrong, but aren't
NiMH batteries immune to the memory effect?

"James Sweet" wrote in message
news:Um0sf.13709$x%2.42@trnddc06...
Chris F. wrote:
A customer brought this amusing little item to me on Christmas Eve. He
needed it fixed that day but it just wouldn't have been possible, so he
took
it back to try and get a refund. I'm posting this message just to
satisfy my
curiousity.....
The toy was a remote-controlled flying saucer. The saucer was a
lightweight styrofoam rig with the electronics crammed into a small
space at
the top. Upon engaging the remote, a propeller would start (accompanied
by
blue and red LED's) and the entire unit would spin rapidly and climb to
the
ceiling. Altitude could be controlled by how much pressure was applied
to
the remote control trigger.
At least that's what it did the night he got it home. He had to try it
for
himself before wrapping it for his grandson, and after marveling at the
device he plugged in the charger and went to bed. When he tried it the
next
morning, the device would run but didn't have enough power to lift off
the
floor, even though the batteries should have been fully charged.
The battery pack was a very small NIMH type consisting of five cells.
It
had the specs 6.3V, 150mAh printed on it. Pretty small considering the
load - I hooked up a decent 6.3V gel-cell and measured about 2.2 amps
power
consumption! Not surprisingly, with a decent power supply attached, the
unit
worked fine. When the original battery was used, it's voltage would drop
to
about 5.7V under the load. I tried hooking the battery to a small lamp
(6V,
500mA) and the voltage still dropped to 5.7 volts. The instructions say
the
battery takes 20 minutes to charge - at this point I suspected the
battery
had been overcharged and ruined, and since I couldn't possibly obtain
such a
specialized part on the same day, the project was aborted.
My question is, how much load should such a small battery pack
provide,
without a significant voltage drop and assuming it is not damaged? Do
you
think my diagnosis was correct?




Those use Li-Polymer batteries which can store an amazing amount of
power and can support huge discharge currents, often 10 *amps* or more
for short times from tiny cells. They make possible planes such as these
http://www.hobby-lobby.com/shockflyer.htm which have thrust to weight
ratios of 2:1 or more. Another place you can get this stuff is here
http://www.balsapr.com/


The charger should normally only take a few minutes to fully charge and
they're very sensitive to being damaged by incorrect charging so if it
was left plugged into the (probably very cheap) charger overnight then
the battery was probably ruined.