[NSRCA-discussion] Reducing the odds...
Earl Haury
ehaury at houston.rr.com
Tue Mar 28 02:27:01 AKST 2006
Jerry
To the rear motor support. Air exit is via four 1/2" wide x high "notches"
at the rear to allow air to flow past the motor support. I'll work on some
pics - have jury duty today so it may be a day or two.
Earl
----- Original Message -----
From: "Jerry Budd" <jerry at buddengineering.com>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Sent: Monday, March 27, 2006 10:07 PM
Subject: Re: [NSRCA-discussion] Reducing the odds...
> Earl,
>
> How far back does the foam extend? To just in front of the rear
> motor support bracket?
>
> Any pics?
>
> Thx, Jerry
>
>
>>Nat
>>
>>Fill the fuse nose with foam (wing core type) & spot glue. Cut a motor
>>"tunnel" about 1/4" dia. larger than the motor (1/8" air gap). Hot wire
>>(wire loop on a soldering gun) ducts from the cheek / chin cowl openings.
>>
>>Earl
>>
>>
>>
>>----- Original Message -----
>>From: "Nat Penton" <natpenton at centurytel.net>
>>To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
>>Sent: Monday, March 27, 2006 5:08 PM
>>Subject: Re: [NSRCA-discussion] Reducing the odds...
>>
>>
>>> 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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>>>>>> >>NSRCA-discussion at lists.nsrca.org
>>>>>> >>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>>>> >>
>>>>>> >>
>>>>>> >>
>>>>>> >
>>>>>> >_______________________________________________
>>>>>> >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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>>>>>> 3/26/2006
>>>>>>
>>>>>
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>>>>
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>
> --
> ___________
> Jerry Budd
> Budd Engineering
> (661) 722-5669 Voice/Fax
> (661) 435-0358 Cell Phone
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