TRex 450SE on 3S A123

[Bill Sanford]

I've had quite a few questions about my TRex 450SE running 3S A123 cells and thought I'd talk about my setup.

Here goes...

TRex SE (v1.5)
Scorpion HK2221-6 (awesome motor!!)
13 tooth pinion
Phoenix 35 ESC
3x HS65MG
LogicTech 2100 / S9650
Spectrum AR6100
Align CF blades
Gorilla Gear ( buy them once and NEVER replace again! Why can't they make the whole heli out of this stuff!!! :-) )

This heli was originally a old gray 450X for those of you who can remember that heli... I learned on this heli and it has been crashed MANY times and upgraded along the way to its current state. :-)

Running 3s A123, the Scorpion motor is needed because of its higher KV than the normal 450 motors. This is due to the fact that the 3S A123 pack voltage is lower than a 3S lipoly pack...

The setup works great and power is better than I had with the Align 430XL motor. The only drawback is that the 3S A123 pack is a bit heavier than a 3s lipoly. The A123 pack weighs about 220 grams, but the TRex handles this easily and flies well.

I do run governor mode on the Phoenix 35, but I don't have it set with much headroom, so under hard collective the ESC is running wide open. The governor is just limiting my head speed a bit to save power when just loafing along... I expect that I'm drawing quite a bit more than 35 amps from the Phoenix 35 with the Scorpion motor at full collective, but the CC Phoenix 35 ESC seems OK with it so far. The CC ESCs are really tough and can handle quite a bit more current than they are rated for. I need to install my Eagle Tree and see what it's really drawing in flight... A 45 amp ESC would be better, but I'll run what I have for now...

A 3 cell hump pack layout works well, but it's a bit nose heavy in the 450. I can fix this easily by shortening the tail control rod and moving the tail servo back a bit to balance it out. Just haven't got this done yet. Not a big deal because it flies very well as is...

Flight times are a bit shorter than a good 3S lipoly, but with an 8 minute recharge you can be back in the air fast and the packs are as tough as nails... No more puffed cells!!!

I would recommend good carbon blades because you're loading the rotor disk a bit more with this setup because of the slightly increased overall weight. I have found the Align carbon blades to be very stiff and perform well. The important parameter when judging blade quality is not how much they bend, but how much they twist. Twisting is what changes the blade pitch and causes bogging and loss of performance. Many lesser quality carbon blades seem stiff when bending them, but twist very easily. I read a post about the good $12 carbon blades from dealextreme.com and ordered a few pairs to try them out. Well I just got them and they twist as easily as my Align Pro woodies. I haven't had a chance to fly them yet, but based on how easily they twist, I don't expect them to perform any better than the Align woodies. I guess you get what you pay for...

I am totally done with lipolys now and fly A123s exclusively. With a Mastech power supply and a Honda EU1000 generator, I can recharge VERY quickly and fly as much as I want with just two batteries for each heli. I fly my 600e on 12S A123 as well and it flies awesome too...

If 3s is all you need to charge, do a search for "zip charge" on RCgroups.com to find out how to make a $10 charger that will charge a 3S A123 pack in less than 10 minutes from a 12 volt car battery... These cells are awesome!!

Bill

[Razor_Racer]

I just wish there was an easy and cheap way to get the cells, getting them out of a dewalt pack looks like hard work

[carlo_the_wonder_frog]

I want to try them too.

[ED the HEAD]

I was about to post something regarding these A123 cells!... IMO these are the future!
Using a 4S-A123 pack (and eventualy use a smaller motor pinion) would give a bit more available power (without increasing amp draw) and might compensate the extra weight? no?
It really seems they are tough cell, don't puff at all, up to what? 30 constant 50C burst? extreme fast charge but 15 bucks each isn't it?
Can we use these cells (4S) with the Align35X stock ESC?

[KingKow]

Is 3s A123 sufficient? I thought that it needed at least 4S to compensate for the lower voltage? A123 sounds like the future to me.


Cheers

[Bill Sanford]

4s A123 would be too heavy in my opinion. I'm already heavier than a 3s lipoly pack with 3s A123.

You don't need 4sA123 if you use a higher kv motor like the Scorpion HK-2221-6 It is a 4,400kv motor and spins plenty fast on 3sA123... The Align 430XL is a 3,700kv motor.

Since the voltage is lower the current draw will be higher though... The A123s don't care and can deliver much more than you need in this application, but I know I'm on the edge with a 35 amp ESC...

BIll

[cheech91060]

do you know what kind of headspeed you're getting with this?

[KingKow]

Originally Posted by cheech91060

do you know what kind of headspeed you're getting with this?

I am guessing using a 12t pinion, it would be 2817 at medium load. This is based on this calcualtor http://heli.dacsa.net/Calculator/default.aspx . Sounds good enough for sports flying to me.


Other than the weight, any ill effectS?

[Bill Sanford]

Originally Posted by KingKow

I am guessing using a 12t pinion, it would be 2817 at medium load. This is based on this calcualtor http://heli.dacsa.net/Calculator/default.aspx . Sounds good enough for sports flying to me.


Other than the weight, any ill effectS?

I haven't tached it, but I assume I'm at about 2,800 with a 13 tooth pinion. Remember, I'm running governor mode with not too much headroom. I do this to save a bit of power when just loafing along... You could get a bit more head speed and pop just by running 100% flat idle up curve at the expense of a bit of flight time.

I also think that if you wanted more head speed, the Scorpion motor is very capable of delivering more power with a bigger pinion. You would definitely want at least a 45 amp ESC if you increase the pinion tooth count any higher though... I would guess that my peaks are already approaching the 45 amp mark even with my 35 amp ESC...

It's a great flying setup, but may be a bit too heavy for really hard core 3D lovers... As I said, the 3s A123 pack weighs about 220 grams and a light 3s lipoly pack weighs about 170 grams. 50 grams isn't huge, but it is noticeable if you fly hard. That being said, the power is there to power through most any move...

Concerning making the packs... It's not very hard to take apart a Dewalt pack and build packs if you have a bit of soldering skill and some mechanical ability. If you can build a heli and solder connectors on batteries, motors, and ESC, you should have no trouble building packs. Just spend an evening or two researching A123 pack construction here and on RC Groups and you'll have no trouble.

If you decide to do this i would recommend adding balancing taps. There is some debate regarding this but I have found that it's a good idea to balance the packs once in a while. You don't need to do it every time. I use Astroflight A123 blinkys.

Give it a go... you'll be glad you did!!

Bill

[Figure.N9ne]

how accurate is that 220g figure? is that a guesstimate or did you actually weigh it? is that a full assembled back with wires, deans and velcro? the only thing truely holding me back from a123's is the weight but we're talking just 16g more than my kong powers. my kong powers with velcro, and deans weighs in at a portly 204g. 16g's seems negligable.

[Bill Sanford]

Originally Posted by yaniel

how accurate is that 220g figure? is that a guesstimate or did you actually weigh it? is that a full assembled back with wires, deans and velcro? the only thing truely holding me back from a123's is the weight but we're talking just 16g more than my kong powers. my kong powers with velcro, and deans weighs in at a portly 204g. 16g's seems negligable.

Here's the exact weights:

The first pack I made with heat shrink, balancer, wire, connector, & velcro weighs 222 grams. The second pack I made weighs 224 grams.

The Scorpion motor weighs 79 grams, while the Align 430XL weighs 70 grams, but you can remove the front battery tray and aluminum mount, which probably weighs at least 10 grams...

If you're already at 204 grams with the Kong Power packs, the difference would be very, very small...

Bill

[progmancod]

How much flight time are you getting with this setup (exactily)?

[Figure.N9ne]

Originally Posted by Bill Sanford

Here's the exact weights:

The first pack I made with heat shrink, balancer, wire, connector, & velcro weighs 222 grams. The second pack I made weighs 224 grams.

The Scorpion motor weighs 79 grams, while the Align 430XL weighs 70 grams, but you can remove the front battery tray and aluminum mount, which probably weighs at least 10 grams...

If you're already at 204 grams with the Kong Power packs, the difference would be very, very small...

Bill

wow, this seems promising! and these are the 2200 cells or the 1100's?

[Bill Sanford]

Originally Posted by yaniel

wow, this seems promising! and these are the 2200 cells or the 1100's?

They are 2,300 mAh capacity nominal, but the most I've ever recharged back into them is about 2,230 mAh.

As for flight times, there's no way for me to tell you EXACTLY how long you can fly. It depends on HOW you fly. For my style of flying, hard sport flying with LOTS of collective, flips, rolls, etc., I set my timer for 5:30.

Remember, you can fly these cells until the heli won't fly any more and not hurt them... That being said, they do dump REALLY fast. I was at first flying with my timer set to 7 minutes and ran out of gas one flight and actually had to set it down way out in the field. You have great power right up to the end and then it just about falls out of the sky! Almost like flying a nitro bird!

One more thing to remember if you go the 3s A123 route, you MUST set your low voltage cutoff to 2 volts per cell. If you leave it in auto lipoly, you will have issues.

Bill

[pwoodyp]

Very good thread...
Think I'll go A123 when I'm ready to buy batts... w00t

No worry batts! No monitoring while charging, no worries about low volts and they don't disappear into a smelly cloud of blue smoke when ignored! Sounds great and I've found them all made up ready to go with the deans and balancing lead for around $100

For Head Speed's according to the following calulator..... https://www.helifreak.com/showthread.php?t=55471
w/ motor: 430XL @ 3700KV enter a load (efficiency) of 83% I get the following;

3sA123   Head Speed   Pinion 
           2230        11T 
           2432        12T 
           2635        13T 
3sLipo   Head Speed   Pinion
           2500        11T 
           2727        12T 
           2954        13T

[Mac_Heli]

I can't imagine not having the Lipo annoyances anymore... I was about to dump some cash on 3 new batts and another charger, but this thread gave me hope... If the A123 are that good, my 500 and 600 projects could actually happen (I had discarded the idea thanks to batt prices). The park I fly at has electricity on most sheds, so 6 min charges would be fantastic!!! I could fly all day and not mess with any oil/gas/smoke (not that I do that now, I only own a 450s).
Thanks for sharing it Bill, I'm going for it!!!

[XsinkrateX]

for the noobs (me) can you explain what they are exactly?
ty.

[rvsixer]

Bill, really enjoyed your post. Great info!

I too am flying a 450 clone (almost identically equipped as yours) on 3SA123. I am really enjoying higher safety, lower cost, fast recharge, no charger, no generator flying. My most recent experiences detailed at http://www.rcgroups.com/forums/showp...postcount=1961 (search through rest of thread for my entire A123 history)

I am standing my packs upright which results in perfect balance, no weight or tail servo shifting required. But how to get 220g packs, please tell me your secret as mine are all 240-244g AUW .

FYI for subsequent thread replies. Individual cells are readily available at ~$14-15USD each from various retailers instead of purchasing yel/blk 10S bricks. Also, like any battery they should be monitored (especially during 5-6 minute zip recharging). Cost to build with balance leads is ~$55 and 20 min time, so if time is more readily available than money no need to spend $100 (and after my experience so far, my next packs will not have balancing leads as they stay wonderfully balanced if charged correctly) .

[GootyS]

This sounds way cool, how many A123 do you use to make up a pack? Hope thats not a silly question. what chargers are you guys using for these?

[Tom Burgess]

Originally Posted by GootyS

This sounds way cool, how many A123 do you use to make up a pack? Hope thats not a silly question. what chargers are you guys using for these?

3 A123 cells for a 3S pack. I'm guessing any charger that will charge Li-Ions? Im guessing you need something that has a high charge rate though? Around 10 Amps?