[NSRCA-discussion] Reducing the odds...
Michael Wickizer
mwickizer at msn.com
Tue Mar 28 06:54:45 AKST 2006
Nat:
Not nearly as sexy or professional as Earl's solution, but I know somebody
that has used styrafoam coffee cups cut to size and glued in with CA.
Proved to be very effective and a quick install.
Mike
>From: "Nat Penton" <natpenton at centurytel.net>
>Reply-To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
>To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
>Subject: Re: [NSRCA-discussion] Reducing the odds...
>Date: Mon, 27 Mar 2006 17:08:27 -0600
>
>Earl
>Can you provide more detail on the ducts ? Nat
>
>----- Original Message -----
>From: "Earl Haury" <ehaury at houston.rr.com>
>To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
>Sent: Monday, March 27, 2006 4:07 PM
>Subject: Re: [NSRCA-discussion] Reducing the odds...
>
>
> > Jim
> >
> > I've used the datalogger to monitor in-flight performance quite a bit.
> > Typically, during a P-07 flight the low voltage stays above 35v
> > (typically
> > <65A max) and power consumption is in the range of 3000 to 3400 mAh
> > (depending on wind) for an eight minute flight. I've set the ESC min
>volts
> > /
> > cell to 3.0v, but 3.3 would work. These numbers are similar with APC
> > 20x15,
> > 21x14, and 21x13W E props - Hacker C50XL-14 motor.
> >
> > Be observant of motor heating in the Abbra, I saw some pretty high
>numbers
> > with "typical" baffles. Filled the nose with foam (wing core type),
>bored
> > a
> > "tunnel" for the motor, and hot wired ducts. Motor stays very cool now.
> >
> > Earl
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "J.Oddino" <joddino at socal.rr.com>
> > To: <chad at f3acanada.org>; "NSRCA Mailing List"
> > <nsrca-discussion at lists.nsrca.org>
> > Sent: Monday, March 27, 2006 1:16 PM
> > Subject: Re: [NSRCA-discussion] Reducing the odds...
> >
> >
> >> Hi Chad,
> >>
> >> I'm about to launch my first electric pattern plane and I'd like to get
> >> your
> >> opinion on my logic for setting the cutoff voltage. First of all I'd
> >> prefer
> >> that I'd never let any cell get below 3.3 volts per cell. However, I'd
> >> also
> >> prefer that the motor never stopped. My plan is to get to know the
> >> battery
> >> voltage vs. flight profile to accomplish both. I will set the cutoff
> >> voltage very low so it will never cut the motor. I will telemeter the
> >> voltage and current and keep track of the mAh consumed. If I see the
> >> voltage getting too low (<33V)under max load or use more than 80% of
>the
> >> capacity I will land. If I can't get through the pattern I'll probably
> >> need
> >> to go to a smaller prop. Once I am confident that the profile is
> >> consistent
> >> I can remove the TM system. What do you think?
> >>
> >> Jim O
> >>
> >> ----- Original Message -----
> >> From: "Chad Northeast" <chad at f3acanada.org>
> >> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> >> Sent: Sunday, March 26, 2006 10:45 AM
> >> Subject: Re: [NSRCA-discussion] Reducing the odds...
> >>
> >>
> >>> Hi Eric,
> >>>
> >>> Regardless of cutoff, its the resting voltage that is of paramount
> >>> importance for good pack life. A 1C discharge with a 3V/cell cutoff
> >>> will leave you with a very low resting voltage, as compared to a 15C
> >>> discharge with the same cutoff. Recently there has been a number of
> >>> discussions about increasing safe cutoff values as the C rates go up
> >>> since most of the current packs hold voltage so well up until then end
> >>> when they simply dump everything they have....so 3 v/cell now equals
>to
> >>> a much deeper discharge than in the past.
> >>>
> >>> Then there is the problem that the ESC is only seeing average pack
> >>> voltage and not cell voltage...so its entirely possible while under
> >>> discharge to have a pair of cells at 3.2v (6.4 total) and the third at
> >>> 9-6.4....or 2.6V, and now your ESC will cut properly...but that one
>cell
> >>> is being damaged.
> >>>
> >>> If you run a bit higher cutoff (3.1-3.2) and fly so that your open
> >>> circuit resting voltage is 3.75-3.8 you will have very happy
>batteries.
> >>>
> >>> I agree...there is not enough of this information available without a
> >>> lot of online reading. There is a lot of this on RC Groups...although
> >>> it can take a significant amount of time to wade through the BS and
> >>> gather what is useful.
> >>>
> >>> Chad
> >>>
> >>> Grow Pattern wrote:
> >>>
> >>> >Chad,
> >>> > The speed controller cuts out at 9V. It actually drops to
> >>> > about
> >>> >8.3V under load and then settles back to 9.0V after the motor cuts.
> >>> >
> >>> >You know it's not so much that I am reporting what I personally do as
> >> much
> >>> >more like I am stating what the system does.
> >>> >
> >>> >The voltage cut-off end-user value options on the speed controller
>are
> >>> >selectable but still have fixed values. A three-cell pack has to use
> >>> >the
> >>> >9.0V option. I used my in-line meter to monitor and measure these
> >> results.
> >>> >
> >>> >Once again we are back to the instructions verses acquired knowledge!
> >>> >
> >>> >Regards,
> >>> >
> >>> >Eric.
> >>> >
> >>> >
> >>> >----- Original Message -----
> >>> >From: "Chad Northeast" <chad at f3acanada.org>
> >>> >To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> >>> >Sent: Sunday, March 26, 2006 10:30 AM
> >>> >Subject: Re: [NSRCA-discussion] Reducing the odds...
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >>>I now believe that I had a bad cell on the one that blew-up.
> >>> >>>
> >>> >>>
> >>> >>If you were discharging to 3 v/cell as I read it from your data then
> >>> >>its
> >>> >>not surprising that you would have bad cells....a 3v/cell resting
> >>> >>would
> >>> >>indicate that you are discharging much below that under load.
> >>> >>
> >>> >>shoot for 3.7-3.8 v/cell resting (5-10 minutes) after the flight and
> >>> >>your batteries will be much happier, and stay in balance all by
> >>> >>themselves for the most part.
> >>> >>
> >>> >>Chad
> >>> >>
> >>> >>
> >>> >>Grow Pattern wrote:
> >>> >>
> >>> >>
> >>> >>
> >>> >>>First of all thanks for all of the suggestions and advice from the
> >>> >>>list
> >>> >>>surrounding the charging of my Lipo's.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>I have been messing with the big Lipo's since before Jason flew his
> >> most
> >>> >>>notable entry at the world's four years ago. This was my first
> >>> >>>catastrophic
> >>> >>>failure of a battery pack. I have spent around $7000 on electrics
>in
> >> that
> >>> >>>period of time and have closely monitored their technical
> >>> >>>development.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Right now I am working on sport type or sport level electrics. Not
> >>> >>>the
> >>> >>>foamy
> >>> >>>type or super light type of models, but the alternatives to 40
>sized
> >> glow
> >>> >>>motor powered models.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>I particularly like the HIMAX offerings where they sell a motor, a
> >> motor
> >>> >>>mount, a matching speed controller and a prop all in one box. This
> >> saves a
> >>> >>>lot of guessing and previous trial and error on the part of the
> >>> >>>buyer.
> >> You
> >>> >>>are left with the choice of what battery pack and what plane to put
> >>> >>>it
> >> in.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Which brings us back to the exploding Thunderpower 4400 pack. I had
> >> been
> >>> >>>using my Astroflight 109 chargers with great success. I have 4 of
> >>> >>>them.
> >>> >>>This
> >>> >>>was before the little add-on balancers were available. They charged
>a
> >>> >>>bunch
> >>> >>>of different packs up to and including the big 4S3P packs with no
> >> problems
> >>> >>>etc. I am familiar with their warning etc. In particular, it states
> >> that
> >>> >>>it
> >>> >>>is not recommenced to charge a fully charged pack, (note: not
> >> forbidden).
> >>> >>>It
> >>> >>>further states that the charger will shut down the charge after
>about
> >>> >>>4
> >>> >>>minutes if you actually try and do this.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Now we get to the 3S pack in question. I was not satisfied with the
> >>> >>>knowledge of what happened and the comfort of how to prevent it
> >> happening
> >>> >>>again. I did not have another pack, or at least I was not going to
> >>> >>>risk
> >> an
> >>> >>>old friend's second and last pack. I did a couple of things.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>I measured the each cell of my 3600 mAh Tanic's using the voltage
> >>> >>>taps
> >>> >>>that
> >>> >>>are part of the assembled pack.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>CELL UP CELL DOWN
> >>> >>>
> >>> >>>I 4.18 3.01
> >>> >>>
> >>> >>>II 4.18 3.00
> >>> >>>
> >>> >>>III 4.19 3.01
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Charging the pack when at 9.2V gave-
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>CELL UP
> >>> >>>
> >>> >>>I 4.18
> >>> >>>
> >>> >>>II 4.19
> >>> >>>
> >>> >>>III 4.18
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Charging the pack when fully charged caused the charged to read it
>as
> >>> >>>3
> >>> >>>cells. It went through the 3 minute determination pause. Charged
>for
> >>> >>>about
> >>> >>>a minute and said "I'm done!" did this with two different 3600 mAh
> >> packs.
> >>> >>>The charger did what it said it would do.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Then just as an FYI, I flew the model with both packs wired in
> >> parallel.
> >>> >>>One
> >>> >>>pack was giving me 5 minutes of flight at full throttle. I needed
> >>> >>>more
> >>> >>>air-time on the sport plane. (World models Sky Raider). I now had
>10
> >>> >>>minutes
> >>> >>>plus and the flight did not run out of steam.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>The two packs were fully charged and the plane flown for about
>seven
> >>> >>>minutes.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>This created a 3S2P pack. The readings were very encouraging.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>PACK-A
> >>> >>>
> >>> >>>CELL UP CELL PARTIALLY DOWN
> >>> >>>
> >>> >>>I 4.18 3.68
> >>> >>>
> >>> >>>II 4.18 3.68
> >>> >>>
> >>> >>>III 4.17 3.67
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>PACK-B
> >>> >>>
> >>> >>>CELL UP CELL PARTIALLY DOWN
> >>> >>>
> >>> >>>I 4.18 3.68
> >>> >>>
> >>> >>>II 4.19 3.68
> >>> >>>
> >>> >>>III 4.18 3.67
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>The cells were discharging and charging nice and equally.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>My charging practices have been upgraded to.
> >>> >>>
> >>> >>>1. Test voltage of each cell before each charge.
> >>> >>>
> >>> >>>2. Monitor the charge initiation.
> >>> >>>
> >>> >>>3. Place pack on 1/2" metal plate on table outside of van. (Deep
> >>> >>>Cycle
> >>> >>>marine 12V is in back of van).
> >>> >>>
> >>> >>>4. Check reading periodically.
> >>> >>>
> >>> >>>5. Test voltage of each cell after each charge.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>I now believe that I had a bad cell on the one that blew-up. I also
> >> would
> >>> >>>not charge the TP pack without the after-market device. In fact I
>now
> >> do
> >>> >>>anything to reduce the odds of another accident.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Just looking at the display on the 109 charger tells you a lot. The
> >> number
> >>> >>>cells, the voltage during initialization and during charge, must be
> >>> >>>correct,
> >>> >>>or at least in range. Putting the pack in a fire safe place is
> >> paramount.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Regards,
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>Eric.
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>_______________________________________________
> >>> >>>NSRCA-discussion mailing list
> >>> >>>NSRCA-discussion at lists.nsrca.org
> >>> >>>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>>
> >>> >>_______________________________________________
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> >>> >>
> >>> >>
> >>> >>
> >>> >
> >>> >_______________________________________________
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> >>> >
> >>> >
> >>> >
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> >>>
> >>>
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> >>>
> >>
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