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T-REX 500 › T500 converted to A123
12-25-2008 07:29 PM  8 years agoPost 1
tacoturbo

rrApprentice

Kauai, Hawaii

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Merry Christmas everyone. I finally bit the bullet and did a conversion to A123. When I found the Trex 6s pack for $99.99 so I had to get it. I've been running 2 3s packs in series but it just takes too long to charge even with two chargers running at once. I've also found some of my packs develope a hugh difference in voltage wired in series. I've swapped out the ESC for a Turnigy 60amper with switching BEC. Super easy to program using their card, at 45 bucks its hard to beat. Pinion size is a 14 at the moment, I do have 15 and 16 tooth available. I'll need to test to see what works better since I like longer flight times as these thumbs are not 3D capable. The only negative on the Turnigy ESC is the soft start is not that "soft". But I've never smoked a Turnigy unit.
Bummer, I can't fly today due to crappy weather. Oh well, it is Christmas day and I haven't raided the tree yet. Happy Holidays!

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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12-25-2008 08:41 PM  8 years agoPost 2
lugnutz

rrApprentice

trenton,nj

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looks awsome how does the a123 work for you any gear changes to get the head speed you need

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12-25-2008 09:43 PM  8 years agoPost 3
tacoturbo

rrApprentice

Kauai, Hawaii

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Did a hover test in the driveway a few minutes ago. Hmm, not sure about this. I think the pack had a full charge but the headspeed was alittle slow on a 14t pinion. What surprised me was that just giving alittle throttle to climb slowly would bog the motor. I just recharged the pack and will try again. I may play with the pinions today. I have a 12, 13,14 and 15. I know most guys are using the 14 and 15 to keep the same headspeed. Any input? This is my first time with a A123 pack of any kind.

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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12-25-2008 10:25 PM  8 years agoPost 4
tacoturbo

rrApprentice

Kauai, Hawaii

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I know what I forgot to ask. The Turnigy ESC I have asks during the programing phase to use either low, mid or high timing. What do I use for the stock T500 motor? The manual says that the low setting is for a 2 pole motor and mid to high a 6 pole. I have it set to the default mid setting. I don't even know how many poles the stocker is. Thanks.

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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12-26-2008 04:51 AM  8 years agoPost 5
tacoturbo

rrApprentice

Kauai, Hawaii

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Uh never mind,I figured it out. However I'm not happy with the results of the 6s A123 packs. It takes about 42 to 48 minutes to charge at 5a on a Turnigy Accucel6 charger. With a 15t pinion I get about 4 1/2 to 5 minutes of hovering. When I feed in throttle, not punching it, but a moderate climbout the headspeed drops quite a bit. The set up is on a stock motor, blades and everything else for that matter except for the ESC which is a Turnigy 60A Plush unit. I have the timing on medium with a very soft start and the LVC at its lowest setting. I've been putting back about 1,900 into the pack and the voltage tops out at 20.7 volts. I thought I would have close to the same performance as my 3s 2,300 packs wired in series. So far I have about 7 flights on the A123's and don't like it. When the power drops off it's so sudden that I have about 6 to 10 seconds to put it on the ground. Almost makes me feel like I shoulda bought more cheapie HC batteries, those I get good results from. Go figure.

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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12-26-2008 05:01 AM  8 years agoPost 6
BOB WHO?

rrKey Veteran

Downey, Ca.

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Thanks for the info, I'm building a 500.

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12-26-2008 05:01 AM  8 years agoPost 7
Tyler

rrElite Veteran

Chicagoland area

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A123

I believe you will be disappointed with an A123 conversion unless you switch to a higher KV motor, a higher pinion, and an esc that can be programmed to recognize the A123 voltages properly. An A123 does not have the voltage per cell as a lipo, therefore a 6 cell A123 may not be recognized as a 6 cell by the esc. Instead, the esc may see it as a 5 cell.

Tyler

Enjoy things that money can buy IF you don't lose the things money can't buy.

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12-26-2008 06:32 AM  8 years agoPost 8
tacoturbo

rrApprentice

Kauai, Hawaii

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I believe you will be disappointed with an A123 conversion unless you switch to a higher KV motor, a higher pinion, and an esc that can be programmed to recognize the A123 voltages properly. An A123 does not have the voltage per cell as a lipo, therefore a 6 cell A123 may not be recognized as a 6 cell by the esc. Instead, the esc may see it as a 5 cell.

Hmm, good points. Is there a motor and what KV would you suggest? Funny, all the stuff I've read on these and other forums has lead me to believe that the A123 in 6 or 7 cell is the cat's meow. Not so cut and dried. One thing you are spot on about is the voltage recognition. My lipo alarm (multi colored LED) works best set up to see 5 cell pack. I wonder if I should try my 17t pinion for the heck of it. I'm just concerned I'll wind up with 3 minute run times. Also I wonder why my charger set on fast charge still takes 45 minutes plus to charge the A123 6s pack at 5 amps?

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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12-26-2008 08:25 AM  8 years agoPost 9
Tyler

rrElite Veteran

Chicagoland area

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Your charger must be A123 compatible AND have an adjustable charge rate that will allow you to exceed 1C. My charger automatically sets the rate to 1C after telling it what capacity the cells are. I have to manually override the 1C settings.

Typically A123 users add an extra cell or more when changing over from lipo. The problem is that adds more weight and the A123 cells are harder to fit into an airframe.

However, if you add enough cells the voltage goes up and the current draw goes down. As the voltage increases the flight time per capacity also increases because there are more cells to share the burden.

Increasing cell count allows the use of smaller cells.

Final voltage (cell count), gear ratios, blade size, and head speed all play an important role and finding the perfect balance. Now that you have decreased your voltage and weight, you will have to experiment will the other variables, perferrably one variable at a time.

This is the time when investing in good data collecting tools is important so you have hard data to drive your experimenting.

Tyler

Enjoy things that money can buy IF you don't lose the things money can't buy.

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12-26-2008 12:26 PM  8 years agoPost 10
steve 01

rrProfessor

Grand Rapids MI

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your accucel 6 is a 50 watt charger just because you set it to 5 amps doesnt mean it is charging at 5 amps, watch the charger when it is charging your probably maxing out at about 2.2 amps

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12-26-2008 01:16 PM  8 years agoPost 11
Ben-T-Spindle

rrProfessor

Central Illinois

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However I'm not happy with the results of the 6s A123 packs. It takes about 42 to 48 minutes to charge at 5a on a Turnigy Accucel6 charger.
You should charge A123 batteries at 10 amps. If your charger is not up to the task perhaps you need a new charger. I use the 1010B+ balance/charger for my A123 packs. It is much less expensive than the popular TP1010C and has a lot more capabilities. http://www.progressiverc.com/1010B+.html

... BTS

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12-26-2008 08:44 PM  8 years agoPost 12
mmc205

rrElite Veteran

PA - USA

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I did the conversion and found that 14-15T is good for sport/light 3D. with a 14T i think i get around 2500 rpm which is good for my style flying. I use a fma 6S which charges at 10 so the charge takes about 15 minutes.

If your having headspeed drops at high throttle setting, either use a governor with some headroom or run curves and and a large enough pinion to get the headspeed you want at about 75% at low pitch values and adjust your high pitch throttle values to a higher amount such as 90-100%. that will take care of the drop in headspeed at high collective settings.

***Logo 600 vbar***Henseleit TDR vbar***

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12-27-2008 08:07 AM  8 years agoPost 13
tacoturbo

rrApprentice

Kauai, Hawaii

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Thank you for all the great replies. Steve01 is right, I checked the charge rate on my accucel 6 and it sets at 5amp but the charge rate evens out at 2.5. No wonder it takes twice as long. I tried the 15t pinion and still get quite a bit of bogging on even a moderate climbout, thats not even mentioning the short flight times just hovering. And when she dumps it dumps right now! Not a comfortable feeling for me. I pulled out the Turnigy ESC and A123 pack. I wish I had gotten a 7s pack but didn't see one I could buy ready made. Seems the 6s is just too weak to be any good. Just my .2 worth. Crap, I shoulda bought some 6s 1p packs instead. I really want to like the A123 set up but....

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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12-27-2008 10:55 AM  8 years agoPost 14
dfrazier

rrApprentice

Sulphur, La

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You could always get a single cell and wire it up in series to make 7s to give it a try. I bet it makes a difference.

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12-27-2008 07:36 PM  8 years agoPost 15
tacoturbo

rrApprentice

Kauai, Hawaii

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True, but I wouldn't know how to wire it up. Thats not even thinking about to balance tabs. Thanks for the input.

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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12-27-2008 09:29 PM  8 years agoPost 16
michalss

rrNovice

France - Lyon

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Use Imax B8 to charge A123

I use Imax B8 charger with my T500 6S A123 and my T450 3S A123. For both helis it takes 17min to completly recharge batteries equ includes. I use it at 7 Amps. Works perfect. It is also possible to configure charger to cut when car battery under 11Volt.

Stan

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12-28-2008 01:57 PM  8 years agoPost 17
mmc205

rrElite Veteran

PA - USA

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don't lose faith yet taco. keep trying pinions and play with your pitch curves. the rather deep voltage depression of a123's makess you have to use more of a v-curve than a lipo, but you can get the headspeed stabelized. Some folks are also running a governer at 60-80% and letting the governer take care of the headspeed drop. Even with a governor though, the speed controller has to have enough throttle headroom to add a lot of power/volts power during hard collective to keep teh headspeed in check. just make sure you pinion up enough that the headroom is there, but don't go overboard.

***Logo 600 vbar***Henseleit TDR vbar***

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01-01-2009 08:35 PM  8 years agoPost 18
tacoturbo

rrApprentice

Kauai, Hawaii

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Thanks for the help. I hope everyone had a great New Years celebration. You would not believe the smoke from the fireworks. Zero wind and fog made things worse. Visibility was about 10 to 15 feet! I shoulda took pictures but my camera was outta batteries. Anyway I'm still trying to sort out the A123 6s for my 500. I'm running a 13t pinion right now, the HS is a bit lower but for sport flying its ok. I'm also going to order a charger capable of handling 10amps. So far flight times are around 5min, 30 sec.

TT

I don't do 3D....no wait. Oh thats right, I can't do 3D!

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