Rustler VXL on A123 cells? - RC-Monster Forums

Superbasher · **Rustler VXL on A123 cells? -** 12.16.2007, 04:50 PM

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

zeropointbug · 12.16.2007, 05:37 PM

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.

Superbasher · 12.17.2007, 11:51 AM

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?

snellemin · 12.17.2007, 01:32 PM

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.

suicideneil · 12.17.2007, 01:34 PM

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....

Superbasher · 12.17.2007, 03:14 PM

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

snellemin · 12.17.2007, 03:17 PM

I get mine from Bigerc.com.

Superbasher · 12.17.2007, 03:26 PM

Quote:

Originally Posted by snellemin

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.

snellemin · 12.17.2007, 04:00 PM

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

This is two 2s1p packs

ICUBoy · 12.17.2007, 05:45 PM

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

suicideneil · 04:22 PM

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....

ICUBoy · 12.18.2007, 10:57 PM

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!!

suicideneil · 12.19.2007, 10:19 AM

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!

Superbasher · 12.19.2007, 01:26 PM

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

snellemin · 12.19.2007, 01:55 PM

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.