2s and 3s a123 cells in my traxxas rustler and stampede
 

I got a dewalt 28v pack and made two 3s packs and one 2s pack. Running the 3s in my rustler with a mamba max 4600 and 16/86 gearing it is extremely fast with 2.8" wheels and still too fast with 2.2" wheels like I use at the rc track. The 2s pack will probably be used by my daughter for her brushed stampede since I'd have to gear it differently in the rustler to get the speed. I didn't really try the 2s with the mamba max though because my voltage cutoff was set for lipo at the time and was cutting in when trying it out.

For charging so far I've used my multiplex ln-5014 charger set for nicd at 5amps (max the charger will do). Any nicd, nimh, lipo charger will work but you need to stop the charge when voltage gets to 3.8 per cell. I built an adjustable voltage cutoff that works for both 2s and 3s using the parts, board and directions I purchased from Dan for $15 shipped on here - http://www.rcgroups.com/forums/showt...795122&page=19. I still have to wire up the balance connections then try my standard lipo balancer on it. Since my lipo balancer simply balances all cells to the lowest voltage it should work just fine for a123 too.

I am going to try plugging it into my 12v power supply using the zip charge method then later my car battery to charge up in 15 minutes.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Using the 3 cell packs with brushless setup I finally ran a pack fully down today and it must have been 20 - 30 minutes of driving (not counting the breaks here and there). I couldn't use very much throttle at the track because it was dry and couldn't get max speed with the conditions. I do have the brushless toned all the way down in the software (both timing and punch control on the esc) and on my controller I still had to limit it at 75% to be able to pull the trigger all the way. I don't even need to zip charge the packs using a car battery with this kind of run time. A 5 amp rate on my charger is less than 30 minutes anyhow. Who can really use the speed of a faster motor at an off road track? I would have really regretted buying a 5700kv for my purposes. My motor temps were at 180 at some points, the controller around 100, the batteries.. didn't check but they didn't feel warm. Even the 16 gauge high quality speaker wire that was meant to be temporary is ok - it didn't get warm at all. The motor wires do get warm maybe soaking up heat from the motor more that caused by current.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

I got the balance plugs today to fit my lipo balancer. The balancer works fine as I suspected - though hobby lobby initially said only lipo works on the lipo balancer. The charge cutoff device connected to a car battery charges at about 8 amps. The wire is probably 18 gauge and measures 5-6 feet. I started with 20 feet of wire just to be safe and it let 5 amps flow using the car battery, so I just kept making it shorter till it was around 8.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Are you going to be able to zip charge a 2s pack with your voltage cutoff? I know that a 3s pack can be zip charged from a 12v source, but curious to know if your voltage cutoff will step down voltage for a 2s charge. Have you tried zipping from your power supply yet? I have a 30 amp model that I could use for zip charging. Thanks

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Zip charge from a car battery won't work for 2s, but the voltage cutoff does work for 2s. I just plug it into my charger, set for nicd 5a (max that it goes), and turn the dial on the voltage cutoff to the mark I made for 2 cell. It takes about 25 minutes on my charger.

I did zip charge a 3s through the power supply and works fine. The amps were around 8a when I checked at the start of the charge but the voltage was at 11.5 - my converted pc power supply doesn't hold the voltage well at the rate I guess but it charges fine.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

so where did you get the cells from? is it devalt or was it meant to be dewalt? also, what mah are they? 2200? Do they fit in the un modded rustler tray, or do they need the tray to be extended? pity they are too wide to fit side by side...

my battery compartment is slightly longer than the stock rusty one, and just as wide, custom chassis so i cant extend it, but i could possibly widen it if i needed to, with some effort...
love the tape and wooden brace :P

im bandaro by rcg btw...

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

They are a123 batteries from a dewalt 28v pack, I fixed the typo. I didn't modify the battery tray in the rustler though you notice the 3s pack doesn't fit side by side. The length is fine for two cells to fit end to end since the length is nearly the same as a 6 cell nicd/nimh pack. The mah is about 2300 and you can run them down fully to use the entire battery unlike lipos which should have 20% capacity left in them to be safe... so some say.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

What motor is in the Stampede? What sort of run time did you get with the 2s pack in the Stampede?

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

The stampede has a 27 turn motor i think it may be called "stinger". With a 13/90 gearing it seems to last 15 minutes or more. My daughter drives it so I geared it way down to limit speed.

I ran a 2s with a mamba max 7700 and got about 10 minutes run time fairly non-stop on the street. Very fast motor... but thats no suprise. Don't know how much time it would last a the track but probably enough for an entire race. The electric races around here are too short at only 6-8 minutes.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Good to hear that the 2s does well with such a powerful motor. I think a lot of people are turned off by the lower nominal voltage of A123's, thinking they aren't up to the task (admittedly I have had similar thoughts myself while researching batteries).

If you daughter's truck has the Traxxas "Stinger" motor, it is a 20 turn motor just FYI. It's probably not much faster than a good 27 turn motor though.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Im thinking about using a123's in my stock firestorm flux and stock stampede vxl... The flux's esc is for 2s lipo max so I guess I'm limited to 2s1p or 2s2p a123, I dunno. What esc settings are you using on your rustler and pede. I'm trying to get an idea if I will have any problems running 2s1p on my stock trucks and what to set the esc at.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Any esc can handle 2s1p or 2s2p a123. The voltage is 7.2 max, with 6.6 being the average during the discharge cycle. Voltage is lower so the motor turns slower. You may want to get a faster motor or gear your motor with a larger pinion if it can handle it. You don't need to set the esc to handle anything - voltage cutoff isn't too critical with a123. Just stop when the car slows down.

In my rustler I run a mamba max 4600 with 13/87 gearing using 3s a123.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Sorry for the OT, but do you think 2s can be used in TX in replace for NIMH packs?

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Most transmitter require an 8 cell Ni battery which charges to approx. 11.6 volts and is considered discharged at around 9.4 volts. A 3S A123 would be required and works well but will not fit inside the case.


Charles

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

@chadr
How are you soldering the joint in the middle of your pack? I see that you are soldering on the tab on your outer joints, but the middle joint is covered with tape. I want to start making my packs for Dewalt packs also. Thanks for any help.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

DeWalt packs come with all cells joined in series by straps, cut the number of cells needed and fold. Use care not to short cells,cause ends to rotate or tear spot welds lose.

http://www.slkelectronics.com/DeWalt/hints.htm


Charles

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Thanks for the link! That is simple enough for even me to attempt.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

Thanks for the explanation.

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

what kind of cell balancer is the one in the second picture? link?

RE: 2s and 3s a123 cells in my traxxas rustler and stampede
 

You mean the one that shows "hobby-lobby smart balancer and guard 505"? I don't have a link handy but it works just like other balancers that it discharges the higher voltage cells to match the lowest voltage cell in the pack at a max rate of 300mah I think. I bought it for about 10-15 shipped off ebay a while ago.

I was searching in my email for something and came across a link to this post. The a123 battery packs are still working today :) I use the 2s in a stampede and they have been used since I got the batteries. The capacity is down to about 1800 mah but the batteries are fine. I rarely ever connect the balance leads. At times the batteries sit for months. I usually charge them up immediately after use. I don't use the 3s batteries anymore because I don't have any rc cars anymore. I didn't expect the batteries to last 10 years - I bet they have another 10 years left.