Motor Costs Comparison (electrical set-ups)

Thu Sep 16 11:32:25 AKDT 2004

Morten,
I totally agree with your assessment.  Keeping the cells balanced is a must.
I'm happy to see someone is addressing that problem.  Keep us posted on the
life of the packs using the EMCOTEC balancing device.
What is your assessment of the outrunner with an 18 inch prop vs. the
Hacker/gearbox and 22 inch prop.  Was Bernd B. handicapped?

Best Regards, Jim

----- Original Message ----- 
From: "Morten Laugesen" <morten at laugesen.nu>
To: <discussion at nsrca.org>
Sent: Thursday, September 16, 2004 10:11 AM
Subject: Re: Motor Costs Comparison (electrical set-ups)

> Hi Guys,
>
> I have no real first hand experience with the electrical set-ups, but I
have been searching the web
> and talking to one of the electrical Pattern gurus in Germany to gather as
much information as
> possible because I think the future in pattern is electric. At present I
will not switch because of
> the relatively new and unproven technology, but I find the development
very interesting.
>
> The biggest issue with the electrical pattern models is the batteries used
for propulsion of the
> model. They are now almost 100% of the LiPo type because of the very high
energy density compared to
> NiCd or NiMH.
>
> One of the biggest issues with LiPo cells is voltage balancing of the
cells. The single cells cannot
> tolerate a higher voltage than 4.2Volts, any higher and you reduce the
lifetime of the battery. This
> means that the LiPo charger observes the voltage of the battery and stops
charging when the cell
> voltage reaches 4.2V. Hence in a 2S1P pack (2 cells in series and 1 in
parallel) the cut-off voltage
> is 8.4V. Here comes the problem however, IF the cells are not completely
balanced you risk that one
> cell has a voltage of 4.15V and the other a voltage of 4.25V when the
charger stops. This means that
> one cell is undercharged and the other overcharged. This is where the
LiPo's get dangerous since you
> risk both reducing the cell lifetime, but even worse you risk that the
cell catches fire because
> it's being overcharged. This problem only gets worse when using more cells
in series. Most of the
> LiPo packs for pattern have a 10S3P or 10S2P configuration, and that means
that the no-load voltage
> @ full charge is exactly 42.0Volts. Maybe one set of parallel cells have a
voltage of 4.0V and
> another set a voltage of 4.4V, but this is NOT noticed by the charger!
>
> In Europe a German guy has developed a small circuitry (called a LiPo
balancer) that can be soldered
> onto every parallel group of cells (10 circuits needed for a 10S3P or
10S2P battery) that starts
> discharging (335mA discharge current) the cell when the voltage rises
above 4.2V, at the same time a
> small LED starts to flash to indicate that the circuitry is in function.
When using this circuit all
> LEDs should theoretically start to flash at the same time if the battery
is completely balanced.
> Otherwise the small circuits will make sure that the cell voltage stays
below 4.2V for the fully
> charged cells and let the other (undercharged) cells reach 4.2V before
stopping the charging
> process. However this means that you need 10 pieces of LiPo balancers for
every pack you have...
>
> Thunder Power claims that their cells are balanced and stay balanced for
the lifetime of the battery
> pack, but how can you be sure of that when you cannot check the cell
voltage? I know of at least one
> guy that fitted LiPo balancers to his Thunder Power pack only to discover
that the pack was indeed
> not balanced perfectly. I'm not trying to slam TP, but I have my doubts
that their cells stay
> balanced perfectly throughout their lifetime. There is no doubt that they
have a system that works
> great, this has been proven by Jason and most recently the Matts, but what
is the longevity of LiPo
> batteries that are not being balanced regularly.?
>
> Just recently I was made aware that the German company Emcotec has now
released a new line of the
> LongGo LiPo packs for use as propulsion in electric models, and they have
included some interesting
> features. First of all the packs have a Sub D plug for a special balancing
module, which is
> connected to the packs only during charging. This module is essentially a
separate LiPo balancer,
> which is only connected during charging, meaning that you only need as
many balancing units as you
> have chargers, and not one set for every battery pack. Furthermore the
voltage for the receiver and
> servos is also taken directly from two sets of parallel cells in the
propulsion battery. This means
> that you only need a voltage regulator to bring the voltage down to 5.2V
to 6.0V depending on your
> preference. This simplifies the set-up and gives you a much more secure
way of handling the
> batteries since overvoltage on the single cells is avoided.
>
> Bernd Beschorner (German pattern and TOC competitor) used the Emcotec
LONGGO 10S2P battery pack at
> the European Champs 2004 in his Plettenberg powered Composite ARF Impact
with great success (placed
> 5th overall), so apparently this system works as well. For more
information on the LongGo packs go
> to this site and press the LongGo button on the left and scroll down to
the bottom of the page.
>
> http://www.rc-electronic.com/endkundenshop/index.html
>
> The battery used by Bernd is the LONGGO Flugakku 10S_2P 37V 4000mAh SBC.
The information is only in
> German, but the picture of the pack should give you a good impression of
the product.
>
> In any case there is a lot of development going on at the moment, and
hopefully the reliability of
> the cells will increase and the price drop.
>
> Sorry this got a little long, but I thought it could maybe interest one or
two of the technology
> nerds (myself included) among you. ;-)
>
>
> Best regards,
> Morten Laugesen
>
> e-mail: morten at laugesen.nu
> URL:   http://morten.laugesen.nu
>
>
> ----- Original Message ----- 
> From: "Jerry Budd" <jbudd at QNET.COM>
> To: <discussion at nsrca.org>
> Sent: Thursday, September 16, 2004 11:36 AM
> Subject: Re: Motor Costs Comparison
>
>
> > Vince,
> >
> > I don't think that's a good assumption at all right now.  In the
> > month prior to the Nats this year I went through three battery packs
> > (fortunately they were all covered under warranty and Thunder Power
> > quickly replaced them with new).  Once at the Nats I made a few
> > changes to the cooling, changed out the motor and speed controller
> > with new zero time spares, and had no further problems.  In fact, I
> > flew all but one of my contest flights at the Nats with the same new
> > battery pack (in round 3 of the finals I had to use another pack
> > because of the short turn time between flights).
> >
> > I do think we'll get there with respect to battery reliability and
> > longevity, but by no means are we there now.  Maybe by the end of the
> > year or sometime next.
> >
> > I've had no failures during charging IMO because I'm so anal about
> > tracking battery temps and voltages post-flight (most of which I
> > learned from Tony Frackowiak).  If something looks out of place I set
> > it aside in favor of another pack and send in the questionable pack
> > (most of the time it's pretty obvious when something's gone wrong).
> > Also, even though all of my failures occurred in flight, I've never
> > "lost" a flight akin to a deadstick landing or a flameout with a glow
> > setup.  I noticed a drop in power, but never a complete system
> > failure.  While typically I immediately landed, in most cases I could
> > have continued the flight by managing the reduction in power with
> > smaller more compact maneuvers than I might have otherwise chosen to
> > fly.  I think most people who saw me fly at the Nats would tell you
> > that I made NO attempt to fly small, so downsizing maneuver geometry
> > a bit to finish a flight isn't at all unrealistic.  FWIW - I don't
> > recommend continuing to fly with a failed battery (really a damaged
> > cell) as a matter of practice due to the possibility (albet low) of
> > the cell catching fire in flight.
> >
> > The above experiences were gained over 49 flights with Tony F.'s
> > ePartner during the month immediately prior to, and including the
> > week of the Nats.  Tony has well over 300 flights on the ePartner
> > since first flight in January, and he's had more problems that I did
> > (he's failed at least one controller and one motor in flight), but
> > understand he's been pushing the technology harder than anyone.
> > Jason did it first and vividly demonstrated the potential.  Tony's
> > been demonstrating the viability.  There are completely different
> > issues associated with the later that take time (meaning a whole
> > lotta flights) to fully "flush out".
> >
> > BTW - Thunder Power and Hacker Brushless USA have both been great at
> > supporting us in this endeavor, not charging for repairs or
> > replacement, even when it's unclear what caused the failure, the
> > electronics or the batteries (sometimes it's hard to separate the
> > cause from the effect, or even which is which).  And FWIW, I'm not
> > sponsored by either.
> >
> > Note to Robert Gainey:  In the above paragraph, substitute "chicken"
> > for "cause" and "egg" for "effect".  That'll make it easier for you
> > to follow.   : )
> >
> > Thx, Jerry
> >
> >
> > >Bob:
> > >
> > >Good job.  It will be very nice to get the the electric option in
> > >your spreadsheet.  I think is fare to assume that the battery will
> > >last about a year.
> > >
> > >Thanks,
> > >
> > >Vince
> > >
> > >-------------- Original message --------------
> > >
> > >Had some questions from the last contest, so decided to do a little
> > >spreadsheet. Just comparing operation of the YS 1.40 DZ to the OS
> > >1.60 (performance being roughly equal, according to feedback I've
> > >received from observers of my setup).
> > >Not starting some battle; just providing some information that some
> > >may find helpful.
> >
>
><http://www.rcaerobats.net/MotorCostComparison.htm>http://www.rcaerobats.ne
t/MotorCostComparison.ht
> m
> > >
> > >Bob Pastorello
> > ><mailto:rcaerobob at cox.net>rcaerobob at cox.net
> > ><http://www.rcaerobats.net/>www.rcaerobats.net
> >
> >
> > -- 
> > ___________
> > Jerry Budd
> > mailto:jbudd at qnet.com
> > =====================================
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> >
> >
> >
>
>
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