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A123 on board battery system

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Simplicity is back!
"A123 Systems" nanotechnology cells carry convinient maintenance capabilities, exceptional safty features and long life not found in currently used battery packs. Why just not give them a try?

     Early spring 2006 -- the crash of my most valuable scale glider  - the SZD55 in 1/3.5 scale was the reason to create this page. It appeared that the defeat of that beauty was due to battery failure. Rest of the last year's flying season was an obsession with battery issues.  Obtaining the marvelous Pulsar 2.07 charger in mid summer 2006 turned out to be my personal breakthrough in attitude toward batteries we commonly use. Pulsar's analytic ability was turning my confidence in batteries lower and lower. I have checked about 3 dozens of mid and high capacity batteries from variety of suppliers and makers ... well.  Without hesitation, any further use of high capacity NiCd or NiMh I had to put on hold. Until  someone will develope balancing / voltage monitoring device to charge and closely monitor each cell under the real load my use of this cells will be sporadic.  If you still want to learn about the CdNi and NiMh reality check  this "Excelent Writng" For extreem load aplications met in our large scale gliders there is no other choice then to look for something to replace commonly used NiCd(Mh) batteries.
     I have heard about new (LiPh) cell technology coming, but I was not familar with A123 cells at that point, Pulsar had that option to charge A123 cells in its software and it was burning my mind to give  them a try. In October 2006 I have begun my own Journey with NANO Technology from "A123Systems".
 
check this out!

p1012199vf.jpg

               
             A123 Systems M1 cells
 
       These retro looking cylindrical cells do not remind any of current shiny and colorful shrink wrapped NiMh or Lithium cells. Bulky and heavy, they seem like no competition to current attractive and compact LiPo. It is all true until you get hold on them and start to use them
 
 
 
How would they serve as an On Board Receiver Pack ?
 

 

Conclusion - Cons
As of 12/22/2009 ( 3 years later)
* I have decided to place this subject first to let the people being aware of the potencial problem especially when scale model instalation requaiers planning and consistent attention to the details of radio gear installation. 

As of 06/02/2010
 
Large portion of the text here is misssing from this page and I do not know why.
Provider has some history in this matter
I will try to restore the thought presented here, but it will be difficult to recall every thing mentioned here. ZM

Conclusion - Pros
 
* Very, Very low impedance. Voltage dropout during load is practicaly non existent. This is sometnig we have been strugling for over 40 years using NiCd and NiMh cells. A123 cells deliver constant voltage no matter what load of this cells is.

* 100% efficiency, No self discharge. There is no capacity loss between the charge and discharge modes. Once the cell is formatted and properly charged it could sustain a charge for 5 years! Well.. is hard to prove, but one of my packs is hooked to Voltmeter for 3 months now. Taking 3mA to support its own LCD it still measures 6.43V. Pulsar charges A123 cells up to 3.65V (peak) and discharges them to 2.8V per cell. Between these two voltage levels resides most of the cells capacity. It translates to 2150mA (94%). The remaining 6% capacity is spread above and under these limits. Creators of A123 cells state that the above 4.2V and under 2V limits should not to be passed in order to keep these cells healthy and long-lasting.
 
* Cells are not poised to get bad during the flight (discharge mode)
You migh find it interesting, but only time when cel gets bad is overvoltage (higher than 4.2Vper cell) during the charging proces or be left out discharged under 2V. You got strong control over cell condition as long your charger is capable to do so. 
 
* Workable Voltage is between 6.75V - 6V. However charger brings 2S packs to a 7.3V level at first, pack stabilizes at the 6.75V shortly after charging is terminated. This is lower than a fully charged 5 cell CdNi or NiMh. Voltage discharge slope is minimal (0.75V/2Ah) and remains constant until the 6V level. Below 6V only 100mA remains in the system. This is enough to land. I found a beeper which goes on when batteries reach the 6V level.  It is a cute safty device.
 
* Weight of these cells is about 2/3 of average CdNi or NiMh pack of similar capacity and voltage (5 against 2 cells). This is a noticeable saving. 
 
* Life span is declared to be 1000 cycles under nominal circumstances. There is no prove in real life to get to this number, but one of my packs is getting 36th charge and there is not even slight drop in capacity. There is a push to charge these cells with high current and use them to pull 70A out. In our aplication abuse of this cells is not a case.

* Charge current could be elevated to not yet considered levels. Pulsar's 12A capability makes this process a blast. It takes about 7-9 minutes in fast mode to charge 95% of capacity back in without much of the heat being generated. COOL! VERY COOL! In our application we will charge our batteries at any level of discharge. I do not see any reason to discharge this cells empty. They perform very well being charged to voltage peak detection from any level as long cells are properly balanced at the end. Use of "Blinky A123" balancer from Astro Flight does the trick very well. A123 cells keep the balance very tightly. Use of EQUALizer from Elprog further shortens the charging time and most of the time there is no need for post charge balancing. You done in 7 minutes pushing back 2000mA

As of 12/22/2009 (three years later)

*A123 cells are very robust. You can overcharge them, you can under discharge them. They are phisycally bullet proof and doing very well in vibration enviroment (tugs). The only thing you have to avoid is to vent them. it is due to overcharge ( safety pop off) or mechanically puncture them or short them on the body  and hole shows up through the can. Cell will not show loss in capacity at first, but gradual oxidation inside the can will put these cells to the rest. I had one case of cell being factory not sealed properly. She did not last a month.

P1013544.jpg

Simple comparizon of NiCd cells with 2300mA A123 pack
On left subC 2200 mA 5 cell pack. A123 cell is as long as 4cells of subC, but thick as C size cell. C size cells 3600mA( nominal - they never had more than 2800mA) on the right. Size/capacity is evident.
 
You can see variety of connectors attached to the A123 pack:
 
1* Deans connector is used as main charging hookup - currently 7 minutes with 12A current
2* Balancing and testing plug
3*& 4* Power Supply for Rx
5* Voltage monitoring and Alarm
 

P1013552.jpg

Current crop of balancers and chargers are able to estimate state of the charge very reliable. I don't know how other brands do that, but Elprog EQUALizers are very precize in this matter and practice proves relibility of these estimates. You can use these balancers to see (as test stand) and record voltages under the load on the computer using suplyed software.

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