Motor Costs Comparison (electrical set-ups)

Thu Sep 16 09:11:28 AKDT 2004

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.net/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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