[NSRCA-discussion] Reducing the odds...

[Grow Pattern]

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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