Best battery choice? + Current Draw used per flight + more testing

[JOddino]

I've got a new column coming out discussing the life of Li-Ion.  It looks
like they build up internal resistance over time so what you will see is a
lower voltage when you test with a load.  The pack I ran all last year still
works but the voltage is so low I've replaced it on the control system and
use it on the ignition system.  It will be interesting to see if and when it
really fails.  I've had this pack almost two years and who knows when it was
made.  Li-Ions will all need to be replaced in the two to three year range.
The good news is the process is very slow and we will know when it is time
to replace them, more so than NiCds.
Jim
----- Original Message -----
From: "Brian Young" <b4598070 at yahoo.com>
To: <discussion at nsrca.org>
Sent: Friday, April 18, 2003 6:31 AM
Subject: RE: Best battery choice? + Current Draw used per flight + more
testing


> I wanted to followup with my latest results from
> initiating this thread.
>
> I changed the aileron servos from the old digitals to
> new 8311s and the current draw dropped to 1.5 A at
> idle (was 2.5-3A with old servos). Running the plane
> to wide open saw a slight reduction in current draw,
> 1.3 A at wide open. Disconnecting the new aileron
> servos and the current draw drops to 0.9 A at idle. If
> I can hold the rudder servo, dampen the shake, the
> current draw would drop to 0.5 A (Aileron Servos
> Disconnected), same with elevator.
>
> All this pretty well adds up, with new Ail servos I
> get 3 18 minute flights on a 1400 mah pack, so I know
> I have little reserve in the pack at the end of the
> day. I either measured what was left after a flight,
> or measure what I put back in to top the pack off. The
> pack cycles at 1350 mah. If my current draw is 1.3 A
> average through an 18 minute flight, thats 390 mah per
> flight. So thats 1170 mah used per 3 flights. Well, I
> always land with a little fuel in the tank, I now know
> by the end of the day Im landing with just a little
> mah in the battery, not enough I imagine.
>
> I may change my rudder and elevator servos as well.
> That 4000 mah li-ion pack is still attractive. I could
> fly 5 times and have half the battery capacity left.
> My concern with the Li-ions is that I know when its
> time to throw away the ni-cads, how do you know the
> li-ions are warn out?
>
>
>
> --- Dean Pappas <d.pappas at kodeos.com> wrote:
> > Hi John,
> > Linking the ailerons on a plug-in ship will be tough
> > without funnies due to wing wiggle.
> > You're right, running the linkage close to the tube
> > will help, but it still won't be easy.
> > Let us know if you come up with somnething.
> > Dean
> >
> > -----Original Message-----
> > From: John Gayer [mailto:jgghome at earthlink.net]
> > Sent: Tuesday, April 15, 2003 11:46 PM
> > To: discussion at nsrca.org
> > Subject: Re: Best battery choice? + Current Draw
> > used per flight
> >
> >
> > Thanks, Dean, for the explanation.
> > I was thinking of the vertical force from the piston
> > rather than the
> > rotational impulse.
> > One of the problems we always had trying to use a
> > single servo was
> > getting a solid slop-free linkage. Perhaps if the
> > linkage were run
> > adjacent to the wing tube the wiggle would be
> > reduced.
> > John
> >
> > Dean Pappas wrote:
> > > Hi John,
> > > The dominant vibration impulses from the engine
> > are in roll. That's the direction
> >
> >   your soft-mounted engine shakes in. Every time the
> > engine fires, the
> > right wingtip
> >
> >   "bangs" upward and the left downward. You'll
> > remember a day or three
> > ago that Eric
> >
> >   noted that the right aileron servo gets beaten up
> > worse than the left
> > one.
> >
> > That's gravity's fault.
> > > Coupling the ailerons would still be a great idea
> > because the air loads
> >
> > are in phase from side to side. One piece wings
> > might be a necessity,
> > because
> >
> >   plug-ins wiggle with respect to each other.
> > > Regards,
> > > Dean
> > >
> > > -----Original Message-----
> > > From: John Gayer [mailto:jgghome at earthlink.net]
> > > Sent: Monday, April 14, 2003 10:18 PM
> > > To: discussion at nsrca.org
> > > Subject: Re: Best battery choice? + Current Draw
> > used per flight
> > >
> > >
> > > I would think the driving function on each aileron
> > would be in phase. If
> > > that is so, then coupling the ailerons together
> > would help a lot. Seems
> > > like it might be worth a try.
> > >
> > > John Gayer
> > >
> > > Dean Pappas wrote:
> > >
> > >>Hi Jim,
> > >>I like that! Frack and I discussed this back when
> > the S9303 came out, 'cause we figured that finally
> > we had one servo with adequate torque to do the job.
> > It still does nothing for the vibration problem: one
> > wing shakes up as the other goes down, but the "G"
> > related load problem evaporates. That one will
> > require second-moment balancing.
> > >>Dean
> > >>
> > >>-----Original Message-----
> > >>From: JOddino [mailto:JOddino at socal.rr.com]
> > >>Sent: Monday, April 14, 2003 2:52 PM
> > >>To: discussion at nsrca.org
> > >>Subject: Re: Best battery choice? + Current Draw
> > used per flight
> > >>
> > >>
> > >>How about Hanson's idea of going back to
> > connecting the ailerons together
> > >>through bellcranks like we did in the old days?
> > >>Jim
> > >>----- Original Message -----
> > >>From: "Dean Pappas" <d.pappas at kodeos.com>
> > >>To: <discussion at nsrca.org>
> > >>Sent: Monday, April 14, 2003 11:06 AM
> > >>Subject: RE: Best battery choice? + Current Draw
> > used per flight
> > >>
> > >>
> > >>Yes, I have considered mass balances on the
> > ailerons.
> > >>I just refuse to leave dangly-things under the
> > wing, in order to do it.
> > >>If i ever come up with a set of mechanics I really
> > like, you will see it.
> > >>Regards to all,
> > >>Dean
> > >>
> > >>-----Original Message-----
> > >>From: GREEN, DOUG [mailto:doug.green at bell.ca]
> > >>Sent: Monday, April 14, 2003 1:36 PM
> > >>To: discussion at nsrca.org
> > >>Subject: Re: Best battery choice? + Current Draw
> > used per flight
> > >>
> > >>
> > >>Have you considered weight balancing your control
> > surfaces to reduce the
> > >>punishment being inflicted on the servos?
> > >>
> > >>Doug
> > >>
> > >>Dean Pappas wrote:
> > >>
> > >>
> > >>>Hi Brian,
> > >>>3 Amps while the mount and possibly airframe are
> > in sesonance is not out
> > >>
> > >>of the question.
> > >>
> > >>
> > >>>What is the W.O.T. current draw? By the way, at
> > idle-shake, the ailerons
> > >>
> > >>are the big draw culprits.
> > >>
> > >>
> > >>>Dean
> > >>>
> > >>>-----Original Message-----
> > >>>From: Brian Young [mailto:b4598070 at yahoo.com]
> > >>>Sent: Monday, April 14, 2003 9:10 AM
> > >>>To: discussion at nsrca.org
> > >>>Subject: RE: Best battery choice? + Current Draw
> > used per flight
> > >>>
> > >>>I found I wasnt getting the capacity I thought I
> > >>>should w/ my 1800 mah 6 cell flight pack. After
> > two
> > >>>masters sequences I recharged and put back in
> > 600mah
> > >>>(triton charger), pack was topped up prior to
> > flight.
> > >>>
> > >>>So back home, I put a current meter between the
> > >>>battery and receiver. I draw about 90 mA with all
> > >>>servos connected, each servo unplugged the total
> > drops
> > >>>by 15 mA, except for the throttle which drops 10
> > mA.
> > >>>Wiggle the sticks and I can occasionally get over
> > 300
> > >>>mah. This didnt seem unusual to me, anyone
> > disagree?
> > >>>
> > >>>So I left the meter in place and started the
> > plane, at
> > >>>idle the meter was reading 3 Amps, yep 3. Has
> > anyone
> > >>>else done this?
> > >>>
> > >>>I move the trottle off idle a little and the
> > current
> > >>>drops to about 2-2.5 Amps, so my throttle servo
> > is
> > >>>bottoming a bit.
> > >>>
> > >>>3 Amps in this gauge wire seems like it should be
> > >>>getting something hot, but I hooked the
> > multimeter up
> > >>>in series with my battery just like I learned in
> > >>>school.
> > >>>
> > >>>The servos are all digital JRs with over one
> > season
> > >>>use, except I did replace the Aileron servos w/
> > new
> > >>>yesterday but havent had a chance to repeat my
> > test.
> > >>>All thoughts on what could be causing this are
> > >>>appreciated. Otherwise a 4000 mah flight pack is
> > >>>looking good to me. Is there any reason a worn
> > servo
> > >>>would draw more current?
> >
> === message truncated ===
>
>
> =====
> Brian Young
> Tulsa
> b4598070 at yahoo.com
> 918-745-6046h
> 918-838-0900w
>
> __________________________________________________
> Do you Yahoo!?
> The New Yahoo! Search - Faster. Easier. Bingo
> http://search.yahoo.com
> =====================================
> # To be removed from this list, send a message to
> # discussion-request at nsrca.org
> # and put leave discussion on the first line of the body.
> #
>

=====================================
# To be removed from this list, send a message to 
# discussion-request at nsrca.org
# and put leave discussion on the first line of the body.
#