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Old Jun 21, 2007, 01:01 PM
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4S Lipo - A123 equivalent?

I'm considering purchasing an A123 stick from my LHS who has a few in stock for use in a Hyperion P-51. I'm currently running a 4S1P 4100mAH battery. Would a 5 cell A123 be a good choice as a substitute for the Lipo?

The LHS is having a 20% off sale this week which would bring the price down considerably....

Thanks for your help.
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Old Jun 21, 2007, 01:17 PM
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Yes, a 5s a123 is a good replacement for a 4s lipo.

The only difference is a lot less mah. maybe a 5s2p if you needed the mah to be higher.
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Old Jun 21, 2007, 01:28 PM
Sparky "Electrics Rule"
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The A123 are only 2300mah.
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Old Jun 21, 2007, 01:34 PM
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How many amps do you pull WOT and cruise? Also how long do you fly?

One of the benefits with a123 is you dont need quite as much mah to equal what your used to.

For example. In my cub i use a 4s2p 6000mah emoli pack. The only reason i went 2p was so i could increase the amount of amps the pack can put out. I didnt really need that much mah.

Now on that same plane i get away with a 5s1p 2300mah a123 pack. Reason being the a123's can put out higher amps no problem. I dont need the extra mah give me a higher amp ceiling. This way i fly for only the time i need and don't it doesnt stress the cells.

This allows you to tailor a pack more precisely to the plane you need. I absolutely love these cells.

,mike

*edit* also the a123's can put out the full 2300mah if need be. On a lipo pack you can only really use up 80% of the pack safely.
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Old Jun 21, 2007, 01:46 PM
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WOT the P-51 pulls about 40A and generates a little over 500 watts of power with a fully charged 4S1P HXT Lipo.

Flying time? *chuckle* until I get tired which is usually about 5-7 minutes. I rarely fly anything to LVC.

I wish I could answer the second question better but I don't normally time my flights.
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Old Jun 21, 2007, 05:00 PM
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Quote:
Originally Posted by ronin4740
WOT the P-51 pulls about 40A and generates a little over 500 watts of power with a fully charged 4S1P HXT Lipo.

Flying time? *chuckle* until I get tired which is usually about 5-7 minutes. I rarely fly anything to LVC.

I wish I could answer the second question better but I don't normally time my flights.
That sounds similar to my cub. I pull WOT about 42A. You probably can get away with a 1p setup. But i would do a decent amount of ground tests first. I like to drain mine at maybe 2/3 throttle static with occasional bursts to WOT and time it. Some advise against running static for any length of time but heres how i figure it. running static is harder on the power system than in the air. If it can survive static then it can survive flight and i have a real world time frame to work with under hard conditions.

Give it a shot see if you like the a123's They are on sale so
Also when switching over do not forget to either disable or set your LVC to nimh. That way you'll get the full mah and not LVC prematurely.

,mike
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Old Jun 21, 2007, 05:51 PM
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Where are they on sale?
Dave
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Old Jun 21, 2007, 06:29 PM
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Your P51 is specked at 3.2-3.6 lbs. Thats amazing light for a plane this size. Have you ever weighed it?

I see no need to use anything thing but a 4 cell lipo or 123. They are so close in performance that going to a 5 cell is not worth it. The Lipo has higher voltage, you can always go up a size in the prop to get more performance from the 123's.

The 123 motor run will be a lot shorter then the your existing 4100mha pack. Depends on your throttle management. Things like this are so subjective that empirical tests are the only way to find out.

Fly the plane for 1-2 minutes, recharge and see how many mah you have used up. From this you can determine if you need more mah. You can easily parallel the 123's into a 4s2p pack if you need it. I don't think you will unless you hold full throttle for the entire flight.

Hobby dealers cannot compete on 123 prices. Learn how to solder and buy the 123's off Ebay for $10 a cell delivered . You have to spend a $100 however for a pack of 10. If you need the 4s2p pack that's $80. Weighs about 20 oz. A 4s weighs half that.

That's why the motor's KV should be known before purchasing. If you run a high KV motor you could use a 3s2p pack for less weight and 4400mha duration.

Trust me on this. Once you use them you will be buying another 10 cell pack for more airplanes.
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Old Jun 21, 2007, 08:06 PM
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Thanks folks. The LHS had sold the 4S and 5S packs yesterday so I used the 20% off coupon I received in the mail for a few other items.

Dave - Everything at my LHS is eligable for the 20% off coupon they sent out in the mail. Unfortunately this didn't do me any good (see above).

Dusty - I haven't weighed the plane but am planning to in the next few days. We have a postage meter at work which I use for this but I haven't taken it to work yet.

I know how to solder wire and have gotten decent at it over the past few years. I've heard that A123's from the Dewalt packs have tabs soldered onto them and that the cans are aluminum. Soldering to aluminum requires different solder than copper, correct?

My 4 or so minute flight yesterday consumed approximately 1600 mAH. I don't think I ever opened the throttle up more than 2/3rds. Thinking about it I guess that a 1P A123 pack would be enough for a minute or two more minutes with similar throttle usage but the 4100mAH 4S1P Lipo will give me another 3-5 minutes at the same throttle setting before LVC.

Finally the motor specs can be seen here: Link I had to cut costs somewhere so I chose to purchase a clone of an Axi rather than a Hyperion motor.

Anyway, I'm getting off topic. Thanks for the advise on teh A123's. I'll probably look at them again for future projects and am sure that the price of loose cells will go down over the coming months.
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Old Jun 21, 2007, 08:31 PM
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my 3.4 lb aerobatic planes go very well on 4 ,a123 cells a good very usable full power (in bursts) flight for me is 8 minutes .
motors are both EFlite 32 align 75 amp ESC w/ parkBec for BEC- props 13x8 and 14x7 - 40+ amps . Yes the VERY expensive 4 cell LiPos will outpower it
a little - frankly I think I have a far more practical setup.
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Old Jun 21, 2007, 09:33 PM
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I would go with a a 6s a123 and re-prop accordingly. That way you will draw less amps and get more duration from a 1p setup.

I'm a heli guy so don't know much about plane setups. All my Helis run a123's, they are the best bang for the buck.
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Old Jun 22, 2007, 10:16 AM
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FWIW, I've found that buying pre-made A123 packs from Michael (mcharles13) is a very painless way to go.

http://www.bigerc.com/

If you create a profile on his website, you will see the special sale pricing available... it's very good, so good that it doesn't make sense (at least to me) to roll my own packs.

I have two 5S1P packs he made and they are working great in my Hangar 9 Cub. It's got an E-Flite 46, has an APC 14x8.5E which pulls 52amps static, and will fly (at mostly 1/2 throttle) for 8-9 minutes easily on one 5S1P pack. I put about 1800-1900 mAh back into it when I'm done.

Granted that's a Cub, not a Mustang, so your mileage may vary

Steve
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Old Jun 22, 2007, 11:00 AM
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sounds good to me -
the part I like is no heat - charge whenever you want -with --whatever amperage you can muster up .
some guys think I should go for a 150 buck pack to get a little more sauce -over the packs I use which ran me 40 bucks each for the four cells used.
I can't see another $100 worth of entertainment and the only contests I attend are with myself (Lord only knows how much I spent on pattern contests n IMAC etc., in 30 years)
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Old Jun 22, 2007, 12:07 PM
Giz
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Quote:
Originally Posted by surfimp
FWIW, I've found that buying pre-made A123 packs from Michael (mcharles13) is a very painless way to go.

http://www.bigerc.com/

If you create a profile on his website, you will see the special sale pricing available... it's very good, so good that it doesn't make sense (at least to me) to roll my own packs.

...

I created a profile but the prices don't seem to change . What gives?
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Old Jun 22, 2007, 02:07 PM
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hi giz. you have to msg me so i can apply the discounts to your acct.

Sorry about the confusion. I will look for your account and update it.

,mike

*edit* i found the acct and updated for you. I'm assuming your Tony. (the only UK acct that was new)
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