[NSRCA-discussion] Reducing the odds...
Earl Haury
ehaury at houston.rr.com
Mon Mar 27 18:14:02 AKST 2006
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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