Are the A123 packs a viable option for 3D or not?

[kenkamm]

Maybe this is an answered question. But I did a bunch of searching and can't say I found a really solid answer, so forgive me if this has been totally covered in the context of the Trex 600.

Thinking of moving up to a 8s Lipo setup so I could also try out the 10S A123 bricks. CC Hv-85, Neu or maybe Z-power motor if I can figure out which one is best. The option of trying out these inexpensive, robust, fast-charging A123 cells is the main reason I am thinking of moving up in voltage.

But the question.... are the A123 cells really up to the 3D task or are they truly limited to sport flying? If the 10S A123 can yield great performance but only for 2 minutes, then I don't know if it's worth it. At that point, maybe I would just stick with the stock motor, esc, 6s setup and save some money.

I don't really want to go above 8s lipo / 10s A123, because then it seems the weight begins to really creep up and the cost is ever increasing...

Thanks,
Ken

[rcmarty]

I'm going 8 cell lipo with the neu 1910/1y motor.
One of the top picks at this time.

Vid is in the video section.

I'm going to try out the 123's also , being there 2300 mah they will work (save voltage under load as a 8 cell lipo) but shorter flight times will be the penalty. I beleive kong (he tested this setup) is running fp evo 3700 brick , gives him 5-6 mins. My ballpark guess is 2300 will fetch 4 mins or a touch more. (lipo's drained to 80% but the 123 can be taken further)

Martin :)

[Finless]

Well I actually got to try them on a 450 last weekend... I WAS impressed with the power but alas the heli FELT MUCH TOO HEAVY!

Multiply this on a 600 and I bet the same would be true. Cant say for sure but I BET it will be true. So you know weight on electrics IS important and can be FELT even by new flyers.

My judgement on the 600 is on hold but if it was anything like the 450.. Naa... I was NOT impressed unless your just hovering around, learning, and doing BASIC FF stuff. After that... the bird will do some 3D but it was just feeling BAD! Like trying to throw around a BRICK!

Bob

[rcmarty]

I can see how 3 or 4 of the 123 cells would weigh down a 450.

But the 123 cells are 70 grams a piece , so that puts a 10 cell pack at 700 grams + shrink and wire. I've heard some reports of the ready to go packs in the 750 range.

6 cell 4900 evo is 752 grams
6 cell 5000 xtreme is 726.

The evo 3700 8 cell brick i've been told is close to the 6 cell 4900's

In the ballpark ...

Martin :)

[kenkamm]

I had the same findings as Marty. From what I have read on the forums, it looks like the weight of the 10s A123 brick won't be that much higher than the 8 cell Lipo. So, if the current capability is there, I think the performance should be good.

I need to go back and find the graphs for the A123 cells and see if they can deliver similar current to a high quality 8s 3700 Lipo.

[kenkamm]

Where would be a good place to buy a neu 1910/1y motor? Seems like some of the ones I have found on various sites are being sold for more than the neumotors.com web site lists them for. Other places list them, but out of stock.

[kgfly]

On a T600 weight won't be a problem but peak power will be for 3D.

You can find the specifications here: http://www.a123systems.com/html/products/cells.html

and the discharge curves here: http://www.a123systems.com/html/products/ANR26650M1specs.pdf

For high performance on a T600 I believe you want peak power of about 1800W. On a 10s A123 setup at about 40A you will get over 1000W but the cells will heat up fast and the lifetime will suffer. There is an interesting whitepaper from FMADirect about their performance tests on A123 cells: http://fmadirect.com/support_docs/item_1229.pdf

The rough guidelines from their tests were that for a lifetime over 500 cycles, keep the continuous load below 30A (13C), for around 200 cycles, 38A (16.5C) or around 40 cycles, 46A (20C).

Avg load / avg voltage / avg power for 10s / no. cycles
30A / 2.81V / 843W / > 500
38A / 2.72V / 1033W / >200
46A / 2.62V / 1205W / >40

For a 8S 3700 20C lipo you should get

50A / 3.2V / 1280W / >50
74A / 3.0V / 1776W / >30

So unfortunately, if this analysis is accurate, I think the answer is that A123 cells are probably fine for sport flight but not up to the challenge of wild 3D. Current generation LiPos outperform LiFe in high power applications, but will typically have shorter lifetimes than A123 operated within their sensible range.

[kenkamm]

Ken,

Thanks for the detailed post. I have to read and absorb all that.

I think, from what I have read, that people have seen performance beyond what the data sheets might indicate. Not sure.

Anyone else running these cells, chime in. :)

Thanks,
Ken

[spork]

The white paper Kenneth references is excellent. I think Kenneth draws the right conclusions from the data. However, I'll offer strictly anecdotal data... I switched from 3S LiPo to 4S A123 recently on my T-Rex 450. I'm definitely getting more power with the A123's (but of course I went to 4S and the weight went up significantly). Even with the added weight the extended climbout is significantly improved with the A123's.

My reason for going to the A123's is partially for added power, and partially because I feel they're more robust, both physically and electrically (i.e. one over-discharge won't ruin an $80 pack). I managed to puff a few lipo packs - presumably by mistreating them. Also, my A123 packs run closer to $40. The fact that I'm less likely to burn my house down is a nice bonus as well. You can't imagine how pissy the wife would be if I did that. :mrgreen:

[Finless]

I switched from 3S LiPo to 4S A123 recently on my T-Rex 450. I'm definitely getting more power with the A123's


What! WHAT!
I dont know what lipos you were running but no way man.... When I tested last weekend yea head speed went up due to a little more voltage from 4S but the raw PUNCH from them was no better than GOOD 20C lipos. The added weight was the killer in my opinion. If these could come in at the same pack weight as good 3S 20C lipos then there would be something here, but right now... NOPE! Not for my style of flying anyway and I am sure not for pro pilots wanting good 3D performance!

Bob

[MrMel]

See my post here:

http://www.helifreak.com/viewtopic.php?t=29339

(Its finally a bit warmer here last few days, so I gonna try 13s setup tomorrow again, to see if its better now.)


Im gonna try 15s1p A123 next week, I expect equal performance as my 10s1p EVO 3700.
15s will be a bit heavier (140 grams) then the 10s1p, but if performance is there, Im ok with it.

[spork]

I switched from 3S LiPo to 4S A123 recently on my T-Rex 450. I'm definitely getting more power with the A123's


What! WHAT!
I dont know what lipos you were running but no way man....

I have two of the TP Pro-Lite 2100 packs and two of the Apex packs. You're more than welcome to come and see for yourself.

In the meantime can you tell me the weight of a T-Rex 600 in your favorite configuration?

[kgfly]

MrMel,,

Thanks for that link, very interesting indeed, great to see real-world data. I see you are getting ~1800W from the A123 pack with average currents in the 16C to 20C range which should mean reasonable lifetime (>100 cycles), at least with cold-weather flying to help keep the packs cool. The secret here is the higher number of cells to give the required power without needing excessive current. Obviously this adds weight too so as you say, sport/3D is viable but wild 3D may require even more cells.

[rcmarty]

Well id agree with finless on the trex 450 when comparing the 123 cells with the prolites. I've been down the prolite path with my 450x myself, while the prolites are good packs the 450 is a bit much for them imo. I'd venture to say finless is refering to a evo or tp extreme battery compared to the 123 cells.

kgfly , you have some good info there. I've read that the 123 cells will put out 70 amps. I've base this on the raptor conversions gary at tppacks has been doing with his converted titan's using the 123 cells. He is pulling down some big amps and hasn't said if they were a short lived or not in real life. I'v venture to say no as he has done alot of testing on alot of helis in many configurations without commenting the 123's are short lived. Now i could be wrong if he has recently found all his cells toast , but something like that would be all over the net in minutes.

I hope there a long lived or reasonable long lived pack (say 1/2 life of a good lipo) as im going to give them a try in my t600 and swift heli.

kenkamm .. i'm waiting for ken at rcflightstore.com to get in his shippment of 1910/1y's. Should be here this week coming. He comes in at $200 usd.


Martin :)

[spork]

Well i'm with finless on the trex 450 when comparing the 123 cells with the prolites. I've been down the prolite path with my 450x myself, while the prolites are good packs the 450 is a bit much for them imo. I'd venture to say finless is refering to a evo or tp extreme battery compared to the 123 cells.

I'm confused by this statement. If finless is refering to evo or tp extreme, you can't really be with or against him on comparing A123's with Pro-lites.

Personally, I'm not with or against anyone on this issue. I don't have a horse in this race. I was asked my opinion of the A123's and I gave it. This is my own personal, very limited, non-massive-3Dz experience. I'm not trying to talk anyone into LiPo's or A123's. I've switched to A123's. I'm sure they're not for everyone. If they outlast my LiPo's I'll be happy. If they don't I'll be sad.

[Cryofix]

There is a small trick I learned this weekend with the A123 cells on my 450, I geared down my 450 to 11 tooth which put me flat at 3000 rpm with the 13 tooth i was at 3400 rpm, the problem with the A123 cells is the fast drop off in initial power, they swing down hard in the curve and the flatten for a longer period than lipos. My next test will to be a dual idle setting, setting idle 1 to 85% and then setting idle 2 to 100%, and then gearing back up to 13 tooth.

This will allow me to knock off the first minute or two in idle one and the switch to idle 2 after the initial power burst, giving me what should be a pretty clean 3100 to 3200 rpm straight through at least 9 minutes flight time.

Conventional Lipo wisdom no longer applies with A123, you have to go outside the box, in gearing, curves, etc... They are very good batteries, and I have to say they are equivalent power to my apex packs, no where close to flight power though as I witnessed this weekend FP 3s packs whip the hell out of TP 3 s packs.

[kenkamm]

Oh, crap. The 1910/1Y won't fit between the stock frames, will it! Argh! Looks like the diam is 1.96" and I just measured the heli at about 1.85!"

[geneween1]

None of the 19XX series will fit between the stock frames. the 15XX series will fit right in.

Geneween

[kenkamm]

Hmmmmmmm

So do I change my plans and try a 15xx motor or maybe a Z-Power motor? Or make a little bit of a frame modification? I have some extra carbon scraps, and I just did some quick geometry and found that a .8" long cut-out in the frame up to the motor plate would allow the motor to fit. Then a carbon reinforcement could be added on the outside to compensate.

[rdespins]

Steve Nue recommends a 1515 2Y for 10S lipo... The 19XX series has been getting a bit warm, they are getting revamped with a fan in a few months.

Ron

[spork]

FP 3s packs whip the hell out of TP 3 s packs.

Very interesting. Are the FP's also more robust than TP (e.g. more resistant to damage from over-discharge)?

[rcmarty]

Sorry :oops: , i guess i wasn't to clear.

If compring the prolite packs to the 123 cells i'd suspect the 123 would feel better.

If comparing the 123 cells to a evo or extreme pack , the weight of the pack would be felt as the newer gen lipos deliver.

kenkamm .. to fit the 19xx series in the t600 you will need to do a minor cut to the frames to fit. I haven't done it yet but i understand it's about 1 inch wide cut that allows the motor to fit.

I'm sure there's a thread out there with pics of the cut , try a search.

MArtin :)

[ozace]

I have been playing with A123 longer than most. First i wouldnt try them on a trex 450, its too small to carry the weight and be happy. It will and does work as seen in some of the posts above but its not ideal. For the 600 if top 3d performance is required then FP packs are the way to go. I have been running the A123's on mine for months and they work very very well for me but i cant and dont 3d.

Its all about what suits your needs. If you want decent sports performance and safe packs then A123 is worth a try, on the other hand if you want mind blowing power then FP lipo's and deep pockets is all thats required.

[Cryofix]

FP 3s packs whip the hell out of TP 3 s packs.

Very interesting. Are the FP's also more robust than TP (e.g. more resistant to damage from over-discharge)?

That I could not tell you, but the sound and the power of the 450 was dramatically different between the 2 packs, the TP packs were the 2100 Mah not the new Extreme packs so there may be a difference there.

[spork]

i wouldnt try them on a trex 450, its too small to carry the weight and be happy.

My T-Rex is carrying them, and I'm happy (so far). Interestingly, a T-Rex with 335 blades and 4S A123 pack has almost identical disk loading to a T-Rex 600 with LiPo's (and no one seems to feel it's too heavy).

But, as I've said, use what you like.