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e-Electric General Discussion > 4S A123 on a Trex 450 or Blade 400
 
 
accidental3d
New Heliman
Location: willow springs,il

Can anyone tell me if I could put a 4S A123 on a stock Trex450 or Blade 400. Would motor or ESC be fried? Did a search on this and did not find an exact answer. Thanks in advance.
09-11-2008 03:39 AM
 
 
702nitro
Key Veteran
Location: Las Vegas, NV

It depends on the ESC recommended input voltage rating. A fully charged A123 cell is 3.6 volts, so a 4s1p would read 14.4 volts(fully charged).

With the motor it's the same thing. For example, the Align 430XL motor accepts an input voltage range between 7.2 - 14.8volts.

I don't want to be the person to put you down, but 4s a123 is quite heavy. I've toyed with 3s a123 on my 450 before and it is definitely nose heavy, with a 4s setup it'll be nose diving for sure, unless you can find a way to balance the rear of the chassis.

Vibe Fiddy
Atom 111110100
Trex 1001011000n
09-12-2008 05:52 AM
 
 
accidental3d
New Heliman
Location: willow springs,il

I don't in any way feel you are putting me down or being negative. I appreciate your response. I bought the Black and Decker VPX 7.2 volt packs. They are weighing in at 86 grams for a 2 cell pack and I haven't removed the wiring and connecters, just all the plastic. So a 4 cell would be about 172 grams for what I am interested in doing. My current 3S lipos average about 150g. I would figure the higher RPM would make up for this. I am looking at sport flying not 3D. CG may become a problem as you mentioned. This is an experiment and I hate to destroy perfectly good electronics without asking questions first and I know there is a lot of knowledge on here. I actually thought the motor would be fine but you helped me there because it is a lot closer than I thought.
09-12-2008 07:55 AM
 
 
702nitro
Key Veteran
Location: Las Vegas, NV

If the Black and Decker 7.2v pack is weighing at 86 grams, it must has to be the lowered capacity A123 cells(1200mah I believe, but not quite sure!). I have the 2200mah A123 cells and each one(cell) weights in at approx 70-72 grams(without tabs).

Yes, you are correct with an A123 setup, if it doesn't have enough volts you counteract that using a higher Kv motor to bump up the headspeed. Problem is, with the lower capacity batteries your using I don't think you'll get decent flight times with any type of motor/pinion combination.

Let me know how it goes!

edit:What motor and ESC are you planning to use by the way?

Vibe Fiddy
Atom 111110100
Trex 1001011000n
09-12-2008 08:27 AM
 
 
702nitro
Key Veteran
Location: Las Vegas, NV

Also,

A123 specs
------------
Fully charged cell(off charger): 3.6
Under Significant Load: 2.85-2.95

Vibe Fiddy
Atom 111110100
Trex 1001011000n
09-12-2008 08:31 AM
 
 
helimatt
Elite Veteran
Location: Lafayette, IN

I'm interested in how this works out too. The weight of the packs as you listed is right in line with decent "C" rated 3S lipos, so no problem

They are 1200mAh though, and if they are rated 30C, then thats just 36V max. I'd be concerned about both short flights and getting rather poor punch out if the cells won't keep the voltage up under higher current draw.

Well, some experimentation with motor/pinion combos might yield reasonable results but flights will be short- maybe 3 minutes max? I fly my lipo setup 5 min of really tossing it around and that's perfect for me. I wouldn't want shorter flights at the same power level.

Maybe instead of 4S, 5S would be better. Set the pinion smaller and lower current draw, Weight increase would not be all that much.

Never, ever, ever, ever give up.
09-12-2008 04:37 PM
 
 
702nitro
Key Veteran
Location: Las Vegas, NV

Heres what I can tell you based on my testing.
Using 3cell A123 2200mah 30c, motor is Align 430XL, Pinion 15.

What I found was that at this setup weight was at the borderline threshold of being to heavy, just imagining how a 4s setup would be, you can just throw out the idea of any sport or 3d flying. With a fully fresh charged pack, doing heavy 3d was possible but it was at the expense of sluggishly moving through manuevars due to the extra weight.

Another thing worth mentioning is the under heavy load characteristic of A123's. Fresh of the charger, headspeed is high and it feels like a lipo. Approx 30 seconds into the flight, the voltage drops significantly enough that obviously headspeed drops as well.
I was getting about 5 minutes(30 second soft3d,4 minutes hovering and circuits).

It's about high headspeed here. Because of weight you'll need the proper motor(kv) and pinion.

Vibe Fiddy
Atom 111110100
Trex 1001011000n
09-12-2008 06:07 PM
 
 
helimatt
Elite Veteran
Location: Lafayette, IN

Yes, but isn't he planning to run the smaller cells? I don't suppose they will sustain the voltage under load even better than the 2200mAh cells tho.

Different motor might give better results- someone has a thread about a Scorpion motor on A123 cells...

Never, ever, ever, ever give up.
09-12-2008 06:51 PM
 
 
702nitro
Key Veteran
Location: Las Vegas, NV

3s a123 2200mah with the scorpion 6 and If I remember correctly 12 or 13t pinion will give you close to 3000rpms. So fresh of the charger the pack will give you 3000rpms, then when the voltage dips it'll probably drop down to 2700rpms.

3s with the scorpion 6 is the optimum setup. If it gives you 3.5 minutes of 3d or sport flying who cares? You can charge it back up in 15 minutes and do it all over again!

Vibe Fiddy
Atom 111110100
Trex 1001011000n
09-13-2008 08:12 AM
 
 
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e-Electric General Discussion > 4S A123 on a Trex 450 or Blade 400
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