Rustler VXL on A123 cells?
 

Hi guys and and gals,
I'm going to be getting a Rustler VXL soon, and was wondering if the ESC will work with A123 cells? as I was looking at getting a 9.9v pack, but will the auto-cutoff still work with these cells? I've not done much reading up on A123 cells, so all I know about them at the moment is that they are a safer chemistry, and the same (?) voltage as LiPo.
Any help/info appreciated.
Cheers
Matt

A standard lipo cell has a voltage of 3.7v nominal, an A123 cell on the other hand has a nominal voltage of 3.3v (this is why lipo's have higher energy denisty, as well, this is why A123's have super long life... low oxidation potenial, blah, blah)

The A123's are very safe, you couldn't TRY to light them on fire (believe me, I have tried!), so you don't need to use the automatic voltage cut-off.

a 3s A123 pack should work great, although, you may want to consider getting a 3s2p pack, as the VXL can draw up to 100amps, IIRC. A 3s pack can only deliver a 'solid' 540watts, you get a 3s2p pack, that goes to 1080watts... that will make the rustler fly. A 3s2p pack will also weight the same as a 7cell NiMH pack and have almost twice the usable energy on tap.

Hmmmm Maxamps don't sell a 3s2p pack, do you know where to get one from? As my soldering skills aren't the best. I can do plugs and stuff like that but not much more. Also you say I won't need the cut off - Does that mean that I can just run them flat?

You don't need to run a voltage cutoff as the power drop is very noticable. When it slows down, you just stop. Word is that you can run 4s lipo on the VXL, so 4s1p A123 should work.

But in anycase, the 3s2p is a great suggestion for bashing. Just get a parallel adapter and connect two 3s1p packs.

Yep, run them till they dump basically- no need to worry about over discharging them; you will need a good charger though with cc/cv settings (any good lipo charger should charge A123s though I believe). You should just be able to use a Parallel Y- cable to hook the two packs together, but A123 cells are a funny size/shape, so it might require a bit of imagination to mount them securely....

Hmmm.... Might be a bit hard to fit 2 3s1p packs to it. Anyone got any good retailers of these packs other than Maxamps?
Also as for a charger, I was looking at either
http://robotbirds.com/catalog/produc...oducts_id=1313

or

http://robotbirds.com/catalog/produc...oducts_id=1423

Any reccomendations on which is better, or any other charger/balancer setups?
Cheers
Matt

I get mine from Bigerc.com.

I've been looking at the 3s1p packs on there. They do them in a stick formation - I take it they are bigger than Normal sub C NiMh's? As I could run 2 in a stock pack formation if they were a similair size.

They will not fit properly in the stock location as they are bigger then Sub-C. But A123 will be releasing a smaller pack that will fit. If you get the FLM chassis that Mike carries, then A123 cells will fit. Look at the 2 pictures below and you'll see that they won't fit properly.

This is two 3s1p packs
http://i189.photobucket.com/albums/z...r/DSCF1089.jpg


This is two 2s1p packs
http://i189.photobucket.com/albums/z...n/DSCF0795.jpg

REALLY nice clean packaging on that Rusto, snellemin. A picture paints a thousand words....

Hehe, I take it there was a pinch or sarcasm with that? I couldnt see the cells in the 1st pic for the velrco & wires! Anyway, A123 cells are a fair bit longer & wider than Sub-C, so fitting them is a nightmare. An after market chassis would be best (the FLM is cheap and very cheerful), that way you could lay them out and strap them down with plenty room to spare, just wont be as neat as the proper chassis with the 'tub' for the batteries to sit inside....

Suicideneil I might be revealing my lack of experience and skill but that really IS clean compared to my emaxx with MM, BEC, Feigao, A123s: it's a big old mess really. The A123s are salvaged from deWalt packs and look like homemade bombs... But it is fun!!

Hehehe, I think theres just an excess of wire in the first pic, but thats not an issue really since sometimes its better to have too much than not enough. I've seen far worse before, so that looks okay by comparision!

That $60 chassis does look good for the price - at first I saw the $170 chassis and wondered what you people call cheap lol

I'm waiting for the extended chassis to arrive. Hopefully my cable routing will look better after that hehheheheh. Really hard to fit 6 A123 cells on the current chassis. I'm hoping that the extended chassis will wheelie less and have a better straightline run.

hey bro check this guy out for a123 batteries he's also on ebay: http://www.thedunemaster.com/

Thanks for that. It seems I have plenty of options for where to buy so i've been doing a bit of simple Math, and you can run a 4 cell A123 pack without going over the motor RPM limit, but I don't know if the ESC can take it. I would imagine so as it can take 200A continuous and 320A peak. Oh and i've got the truck now and I really like it so i'm now going to get the batteries sorted.

Superbasher thanks for replying to my PM, I understand you could not finish your A123 rustler project.

Maybe someone else can help me?

Ideally, I would like to power a rustler VXL with a 3S2P pack. I can afford getting the aluminium extended FLM chassis if it's needed to fit the batteries.

Can anyone tell me how to fit 3S2P cells on the rustler?
Is it possible to fit two 3S1P packs on the rustler and wire them in parallel with an Y adaptor?
If yes, how the 3S1P packs should be? just a stick pack? a hump pack?

Finally, if it is impossible to fit 3S2P A123 on the rustler, what can I do? 2S2P? I would appreciate to get a decent runtime, so I would avoid an xx1P configuration.

Thanks for any input on this matter. A123 batteries are just too good to be overlooked and I would REALLY like to power my rustler with them.

There are several ways of fitting them in. I run 6 A123 cells on mine at times. I did it both with the regular and extended FLM chassis.

http://i189.photobucket.com/albums/z...r/DSCF2869.jpg
http://i189.photobucket.com/albums/z...r/DSCF2605.jpg
http://i189.photobucket.com/albums/z...r/DSCF2287.jpg

I did manage to put 2S2P pack inside my T4, obviuosly that rise CG, but it worth, A123 are easy to work with and almost care free

http://pix.nofrag.com/e/7/6/b1e37181...d20f0a2ftt.jpg

Wow that's really good info, thanks!!

1/ I guess there is no way to fit them on the stock chassis. Do you advise me to go for the regular or extended FLM chassis? I intend to keep the rest of the car stock for now.
2/ Of all 3 pics you have provided, which arrangement do you think is the best?
3/ Is it possible to keep the stock ESC support or do you have to get creative on how to attach it to the chassis?

Sorry for the many ???? but I'm delighted to know the rustler can be run on A123 :party:

I managed to fit 4s1p A123 in the stock chassis before, but it was just a mess.

Both FLM chassis are great, but it's easier to fit 3s2p A123 on the extended chassis. Now how you installed them is up to you. I just installed them towards the front right now to eliminate wheelies.

Many thanks for sharing your experience. I'm going to get an extended aluminium chassis and run two 3S1P packs in parallel :yipi:

it looks like Maxamps have the packs, but they don't tell which formation they are using, bummer! Anyone knows if they are in a flat formation like in snellemin's pictures?

http://www.maxamps.com/A123-99-Pack.htm

I think they are normally in a triangle formation...

I got my packs from Bigerc.com. He welded extra battery bars on my packs to keep the heat down. I use to melt the thin heatshrink off the battery pack from the current draw.

wow. thats some pretty intense current draw snellemin, it would have to be 150-200* C as it only shrinks @ 125*C

Ive got 2 3cells and 2 2cells from him. throw in my parallel and my series connectors and i can run whatever i want.

After all these are too expensive anyway. I just scored a Dewalt 36V pack (year 2008) for 120$. Now I just need to make the packs :oh:

Just be careful some of the newer packs are NOT A123 cells apparently

Thanks for the tip, I got it covered and they are A123 so it's perfect!

how can you tell? thanks...

It's just that the seller opened the pack to check the cells...
Annoying that not all Dewalt packs have A123 cells in them. What cell type have they replaced them with?

Ok I got my rustler running :yes: :party:

I really have to say that I'm extremely impressed by this rustler VXL. I mean for the price you get a RTR model that includes everything, to hear it run is as easy as i can get, yet what you get is a BEAST of acceleration and top speed. It's almost criminal to sell that kind of stuff to anyone who has $270 in hands without a background check :lol: :rules:

I bought the FLM extended chassis along with it. Mounted everything was extremely easy. As I am more used to 4x4, this model just looks so simple and straight forward that my other models actually look very cluttered and messy now.

I initially planned to used two 3S A123 packs in parallel but I have tried to use them one at a time and they work extremely well. Runtime is very useable too, since the car is so lightweight. Unless you are really making speed run repeateadly it's easy to get 20 min of bashing around on a single charge.

Here are a couple of pics of my rustler. All stock except the FLM extended chassis :

http://img243.imageshack.us/img243/3249/img3560yt2.jpg
http://img182.imageshack.us/img182/2650/img3551yi0.jpg
http://img77.imageshack.us/img77/8541/img3553bi6.jpg
http://img77.imageshack.us/img77/548/img3552bq2.jpg
http://img166.imageshack.us/img166/391/img3562pk7.jpg

My only complains are :
- all the scews run directly into plastic parts, no metal inserts, so you need to be carefull not to strip the threads
- the little protection behind the motor broke quite easily I ordered two spares but might also consider a more robust skid plate or something

Bottom line is I would totally recomment A123 for the rustler VXL. Only the FLM chassis is really needed to make this work, since a 3S pack would not fit in the stock chassis. You get some serious power for a very limited budget, and so far it work fine for me. It was very easy to make the packs from a Dewalt 36V since I kept the stock tabs. The rustler seems to have strong enough parts to take the power without breaking instantly.

Besides, charging in 15 min is just too good to be true, yet it is true. OK maybe 17 min is the pack is flat empty. :whip:

Thanks again for your input and cheers!!
Hey do you guys think I am abusing my A123 pack by using them one at a time? Should I stick to two packs in parallel (eventhough the car gets heavier) ?

a few action shots
http://img148.imageshack.us/img148/774/image1ce7.jpg
http://img148.imageshack.us/img148/1073/dsc8669hm5.jpg
http://img164.imageshack.us/img164/8506/image3kg5.jpg

Ooops, looks like I have many questions in addition to this one... Let's summerize my ??? and make it simple for someone to reply :

- is it ok to run a 3S1P A123 pack with the stock ESC and motor?
- is it ok to run a 4S1P A123 pack with the stock ESC and motor?

- is it ok to run a 3S1P A123 pack with a mamba max ESC and 7700kv motor?
- is it ok to run a 4S1P A123 pack with a mamba max ESC and 7700kv motor?
- is it ok to run a 2S2P A123 pack with a mamba max ESC and 7700kv motor?

In each setup I'm worried of abusing either the cells or the ESC+motor, or both. Please tell me what I should not do before I fry everything :lol:

if anyone has answers to these questions I'd greatly appreciate the info
Thanks!!

I run 4s A123 with a unmodified sidewinder and a 2700kv motor. It's fairly insane. temps are no problems, I have two packs and can go straight from pack to pack and run for as long as I want, one on charge, one in the car. Nothing gets too hot or anything, and that was running out in the sand dunes with paddles (ie a lot of load!). Gearing is 30/86.

I also have the extended FLM chassis, I recently installed the FLM gearbox but havent run it yet. I wasn't too impressed with it to be honest, the gear mesh was a lot better in the standard plastic gearbox. I guess I'll see how it goes though. Also, for some reason the shock tower screws you have to use nuts on the other end, the tranny isnt threaded there. I much prefer to use loctite than locknuts. Oh well, its still pretty good. As with all FLM parts I used I had about a million screws and nuts and left over that didnt seem to have a place anywhere on any of the parts I have. Oh well...in the misc screws box they go :)

And for your questions, I havent run those particular combos before, but I wouldnt run anything over 2s (maybe 3s if you want to push it) with the 7700kv motor - or else youll get some serious heat issues. 2s2p is fine, just higher capacity. 3s A123 is less than 3s lipo, which apparently the stock esc/motor is OK with, so 3s A123 would be too. I'd assume 4s would be OK as it is in the castle speed controllers, but couldn't be sure having never used the traxxas one.


Another thing, I noticed you have your batteries very far forwards. This is opposide to me, I put them as far back as I possibly could, and I still have trouble holding traction anywhere but on asphalt. More weight over the rear I say! Wheelies only become a problem when you have traction.

Nice photos btw :)

edit: I forgot to say I've only ever ran 1p, I was running 3s for quite a while, and I agree with you 100%. I think a lot of people on here just want to do ridiculous speeds on ashphalt back and forth with extremely tall gearing - noone seems to think 1p is enough. I even run 7s1p in my revo and it is more than enough power on tap. I don't care how much more power I would get with enerland Lipo cells, I've got more than enough already :P

Thanks for your reply;

you're right, I have some room between my pack and receiver, I will try to push the batteries backward. I have maybe almost an inch of room to adjust. I would like to keep current ESC and receiver arrangement since I find it looks very neat as it is.

Now about the 1P vs. 2P battery configuration, as you said the 3S1P is already a GREAT setup with the stock ESC and motor. Honestly I don't need or want more.

My only concern with 3S1P would be to pull too much current from the cells, which voltage would repeatedly sag under 2V (when under heavy load or accelerations on concrete)... I don't want to abuse them, I know they are robust but I just don't want a reduced lifespan

So : is the stock Rustler too hard on a 3S1P A123 pack sums up my thoughts

thanks for all the other answers. I don't think I'll try the 4S.

3s A123 with the VXL motor is just fine. You will not pull that many Amps out of them with that motor. The peak is only at startup and once your truck starts rolling ampdraw goes down.

Then I'll stick running with a single 3S1P pack, the other one charging. When the first pack is empty, the second is ready and so on... then the fun never ends :party::party:

I have a Mamba Max ESC laying around, would it be a plus to mount it instead of the stock ESC? Not sure if it's better, the stock seems to push it pretty hard already.

Hum... I might still swap for the MM since the later has more braking options. But I'll keep the stock motor, I only have a 7700 motor otherwise.

Thanks!!

The MM esc will give you more power options to play with. You would be able to tone down the power some more, thus increasing run time a bit or visaversa.