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A123 Expert Help Needed - 5/15/2008 11:55:08 AM   
Jack Skip


 

Posts: 151
Joined: 9/8/2003
From: Marsh Harbour, Abaco, BAHAMAS
Status: offline 		I would like to make the A123 plunge, but cannot figure out the setup to get as a starting point. We do not have any hobby stores nearby, so experimenting usually involves waiting 2 weeks for stuff to arrive.

With a Lipo setup the online stores normaly have suggested power systems; Motor, ESC, Prop and Lipo Battery. They often also tell you expected flight times.

What is the best way of "translating" these setups to a A123 setup?

1 - Use same number of A123 cells as the Lipo setup, but prop up to a larger prop.

2 - Add an extra A123 cell and prop down slightly.


I would always prefer a lighter setup, but not if it becomes underpowered. I have read threads where it is suggested at least 400 square inches of wing, which suggests to me most people go for the extra cell and take the weight hit.

I am looking for 3D flying. The plane I am looking at is the Great Planes Reactor Bipe, with their suggested set up; Rimfire 35-36-1200kv, E-Fly SS 45 amp ESC. 600 square inches of wing. 38 ish onces. They use 3 cell lipo and 11 X 7 prop.

What would you suggest?
       Post #: 1

RE: A123 Expert Help Needed - 5/15/2008 9:35:31 PM   
dirtybird


 

Posts: 2911
Joined: 1/25/2002
From: Mesa, AZ, USA
Status: offline 		For 3D flying forget A123's

(in reply to Jack Skip)
       Post #: 2

RE: A123 Expert Help Needed - 5/16/2008 12:30:56 AM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		http://www.rcuniverse.com/forum/fb.asp?m=6041550

In addation I fly an extreme Flight Yak 54E 47" and a 3D Hobby Shop extra 300 SHP 47" both on 4S A123 2300 mAh packs. Both do 3D very well. Only area that is hurt by the extra weight is very slow high Alpha.

Charles

(in reply to dirtybird)
       Post #: 3

RE: A123 Expert Help Needed - 5/16/2008 12:47:49 AM   
Jack Skip


 

Posts: 151
Joined: 9/8/2003
From: Marsh Harbour, Abaco, BAHAMAS
Status: offline 		DirtyBird. That’s a pretty wide statement. Care to elaborate. Is it weight? Power?

Thank You EveryDayFlyer for responding. I was really hoping you would. I have been reading many of your posts and trying to learn from your experiences. I respect your knowledge and obvious intelligence. I also am impressed with your record keeping. You are helping to lead the industry. And I love the way you push the envelope to test the limits of these batteries.

I am kind of looking for a rule of thumb. One cell up and prop down. Same number of cells and prop up. I am hoping to be able to start putting together some A123 systems without having always to see what specific set ups others are using.



(in reply to everydayflyer)
       Post #: 4

RE: A123 Expert Help Needed - 5/16/2008 4:47:10 AM   
dirtybird


 

Posts: 2911
Joined: 1/25/2002
From: Mesa, AZ, USA
Status: offline 		A123's are heavier than Lipos. Sure you can fly with A123's but you will do a lot better with Lipo's for 3D flying.

(in reply to Jack Skip)
       Post #: 5

RE: A123 Expert Help Needed - 5/16/2008 2:58:22 PM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline
quote:

I am kind of looking for a rule of thumb. One cell up and prop down. Same number of cells and prop up. I am hoping to be able to start putting together some A123 systems without having always to see what specific set ups others are using.


Rule of thumb is to add a cell. 4S A123 to replace a 3S LiPoly but truth is that in 98% of case a 4S A123 is a lot more power on tap that an 3S Li.

At say 40 amps. a very good 3S Li might provide 10 volts which equally 400 watts. A 4S A123 would be approx. 11.5 volts or 460 watts. LiPoly will continue to drop in power during the flight but A123 will hold full power to the very end. I get the same level of performance and flight times with a 5S A123 2300 as I do with a 4S 3300 mAh LiPoly if system is set up for 40 amps. max load. The 3300 mAh LiPoly is rated 22-25 C and sells for $136 so not exactly an el cheapo bargain basement one.

My Sig Fazer with AXI 2826-12, APC 13X6.5E
5S A123 2300(13.5 oz.) ,AUW 4.5 lbs. (72 oz) 468 watts peak ,6 min. flights.

4S 3300 Evolectrix (13 oz.) Auw 71.5 oz. 469 watts peak 6 min. flights.

Difference. A123 a whole lot less expensive and based on my past experience will last at least 400 flights. I have no problem recharging A123 in 15 min. with TP1010C or 20 min. with CellPro10. I do not worry about what can go wrong during a charge, I take no special care of A123s at all and they just keep performing great.


FYI The smaller A123 cell as used in the Black and Decker VPX line of tools are great for smaller models. They are listed as 1100 mAh but really are closer to 950-1000. A 4S weighs 6.4 ounces and I have started too use them in place of 3S 1320 Thunder power ProLites in several of my foamies. The extra 3 oz. is noticeable but so it all of the extra power. I get same flight times and other than extremely slow high alpha I prefer the A123s.



http://www.rcgroups.com/forums/showpost.php?p=8727192&postcount=207

quote:

Fancy Foam Edge 540

http://fancyfoam.com/EDGE540HPK.htm


Hi Max 2812/850,GWS SF 12X6 and 4S A123 B&D 1100 pack.

1/2 Throttle 16A 180 watts / WOT 21A 221 Watts.

AUW 18.7 oz. 360 sq. in. wing loading 7.48 oz. per sq.ft.


Flew two flights with 4S 1100 A123 then two flights with TP ProLites 1320 3S folowed by two more flights with 1100s.


Pro Llites 3.2 oz. A123 1100 6.4 oz. IMO the extra weight is not realy all that bad as the extra voltage/ power makes up for it. Extreme slow flight such as high Alpha KE suffers but then that is not really my bag anyway.


I have mentioned this a bunch of times but here I go again.

There is like 100 more times more imformation on these batteries on RC Groups than here.
RCU is OK but I often refer to it as the dead zone.
Charles



< Message edited by everydayflyer -- 5/16/2008 3:08:30 PM >

(in reply to dirtybird)
       Post #: 6

RE: A123 Expert Help Needed - 5/16/2008 3:11:44 PM   
dick Hanson



Posts: 9858
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		How many of you actually fly 3D with A123 ?
I do -it works very well
I use VPXcells on the little stuf and 2300 on large stuf
FWIW the little plane all up is 17 ounces and 430 squares
th e ERATIX weighs 3.75 lbs exactly ready to fly
if you simply keep your weight under control -you get ALL the advantages of the cells .


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< Message edited by dick Hanson -- 5/16/2008 3:15:25 PM >

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RE: A123 Expert Help Needed - 5/16/2008 9:53:27 PM   
Jack Skip


 

Posts: 151
Joined: 9/8/2003
From: Marsh Harbour, Abaco, BAHAMAS
Status: offline 		Thank you all for your input. Still lots to learn.

EveryDayFlyer or Dick Hanson, have either of you experimented with using the same number of cells but proping up as a way to save weight? Just trying to get a comparison.

Kind of like using a 2 cell Lipo on a foamy rather than a 3 cell. I did that before with a foamy and liked the lower weight better than the increase in power from the third cell.

Perhaps the limit is with the amps the motor can pull. The suggested motor can handle 42 amps. At 13.2 volts that would be 554 watts. What if the motor could take 55 amps. Then at 9.9 volts it would be a similar 545 watts. The larger motor would take a weight hit but spin a bigger prop. Bigger prop would have more air flow for 3D. Less batteries makes up for weight hit on motor. Where am I going wrong here?




(in reply to dick Hanson)
       Post #: 8

RE: A123 Expert Help Needed - 5/16/2008 11:21:25 PM   
dick Hanson



Posts: 9858
Joined: 12/12/2001
From: slc, UT, USA
Status: offline
quote:

ORIGINAL: Jack Skip

Thank you all for your input. Still lots to learn.

EveryDayFlyer or Dick Hanson, have either of you experimented with using the same number of cells but proping up as a way to save weight? Just trying to get a comparison.

Kind of like using a 2 cell Lipo on a foamy rather than a 3 cell. I did that before with a foamy and liked the lower weight better than the increase in power from the third cell.

Perhaps the limit is with the amps the motor can pull. The suggested motor can handle 42 amps. At 13.2 volts that would be 554 watts. What if the motor could take 55 amps. Then at 9.9 volts it would be a similar 545 watts. The larger motor would take a weight hit but spin a bigger prop. Bigger prop would have more air flow for 3D. Less batteries makes up for weight hit on motor. Where am I going wrong here?





I prefer to increase volts and also go for shorter flight times .
watch watts and use 4 1100 cells where you did use a 2100 Lipo 3 cell
The advantage?
One pack recharge fast go again - big cost savings .
This is the smallest setup Iwould use but some CZech guys use 3 , 2300 cells ! and keep th plane LIGHT.
I am a bug on light building -mos rtf is overweight -
If you are a buy n fly type- all this may not appeal to you.
Now here is whre you can relly do some good get a HV ESC so you can up the voltage a cell at a time

example a 60 size motor (1200watt) and instead of using a 24 volt ESC get a 50 volt CC 45 amp controller
Now - up the cell count till you get best power -that the motor will take
This is not a sporty put- put setup - this really is for maxed out flying
Anytime you double up the packs -you kill performance
so what do you want
15 minutes of average performance or - 7 mins of great performance.
On little stuff all up under 12 ounces - forget the A123
we fly 3D from 5 ounces on up -so we ain't guessing at this.
IF yo want to try the high amp setups -pulling over 50 amps -go for it but that ain't my idea of a 3Dsetup
Instead -back to the hv setup and prop for 45 amps on the ground - this puts yo right on th ragged edge of full output on the 45 amp controller (best setup) in the air you pull less amps when the model is moving
My friend's 16 cell setup beats the LiPo setups -big time - and flies 8 minutes recharges with th direct charge method in under 5 minutes note that charging time is less than agressive flying time .
Think about it

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       Post #: 9

RE: A123 Expert Help Needed - 5/16/2008 11:28:34 PM   
Jack Skip


 

Posts: 151
Joined: 9/8/2003
From: Marsh Harbour, Abaco, BAHAMAS
Status: offline 		I am with you on flight times. If you are flying on the edge 5 to 7 mnutes is good.

Thanks for the additional explanation. Makes sense. Just wish, given remote location, I could pre figure the equipment I need. Experimenting is quick when the LHS is down the road, not across the ocean.



< Message edited by Jack Skip -- 5/16/2008 11:30:45 PM >

(in reply to dick Hanson)
       Post #: 10

RE: A123 Expert Help Needed - 5/16/2008 11:28:44 PM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		Max motor power (watts) is based on a max. voltage.

20 volts at 50 amps. =1000 watts
This does not mean 1000 watts can be obtained at 15 volts and 66.66 amps.
In general as the amps. go up the effeciency goes down as the motor generates more heats,wasted watts. You are also reducing the capacity of the fuel tank. 3S has only 75% as much capacity as 4S.

Would you believe that my Fazer weighs less than when it had an OS FX .46 on it and flys much better now?

Charles

(in reply to Jack Skip)
       Post #: 11

RE: A123 Expert Help Needed - 5/16/2008 11:33:34 PM   
Jack Skip


 

Posts: 151
Joined: 9/8/2003
From: Marsh Harbour, Abaco, BAHAMAS
Status: offline 		EveryDayFlyer, Looks like our posts crossed.

Ok. That explains alot. Thanks. So, is the sweet spot for the A123 up in the "40 Glow" size planes?

(in reply to everydayflyer)
       Post #: 12

RE: A123 Expert Help Needed - 5/17/2008 12:44:30 AM   
dick Hanson



Posts: 9858
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		Not the "sweet Spot -but a darn good starting poing for most -
I can take a 9 cell setup and run 43 amps roughly (30x43=1290 watts) good for a 6-8 lb model
so the batts don't get pulled hard n all stays kooool

_____________________________

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Libby

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       Post #: 13

RE: A123 Expert Help Needed - 5/17/2008 3:42:13 AM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		A123 2300s AUWs

5S fazer 4.5 lbs. 468 watts
4S Extreme Flight Yak 54E (47" 47 oz. 650 watts
4S 3D hobby Shop Extra 300SHP (47" 47oz. 600 watts
and a few more that are all in-line with above.

Six min. flights and 15 min. charges.

Charles

(in reply to dick Hanson)