Advice needed: Batteries for a 30lb Rampage MT conversion
 

Hey all,

I converted my rampage MT using the kershaw designs conversion. (mamba XL2, castle 2028). It rocks REALLY hard.

My problem is it ate my really nice 5000mah 65-130c Turnigy Nanotech batteries in about 6 runs. They were perfect for about 100 runs in my erevo and converted Losi XXL, but the big boy ate them hard. One cell is now cooked, and the other pack swells during runs.

Obviously, I can't have this. I need advice. Ive had good luck with Turnigy in the past, so I was considering their "heavy duty" 60-120C 5000mah pack. I would get TWO 6s packs and run in PARALLEL (before was using 2x 3s packs in series) which SHOULD get me 600 hypothetical amps to draw without cooking them. I would likely also gear a little easier. I know that it would add about 3.5 lbs to the weight, but I don't really care if it's a little heavier/slower as 6S on this setup is plenty fast enough.

Do you guys think it would work out well? Is there a better idea? Better batteries for something this heavy? I'm afraid that when I brake, it's putting too much voltage into the battery because of the extreme momentum of the weight and speed. Is this possible?

Any insight would be welcome, or if you've ever had a huge truck and had your batteries last, let me know what they were.

Thanks

why not purchase the 8000mah packs that kershaw sells?

Or, I would look into some of the 4S 7500mah VANT lipos and use those in series for 8S and adjust gearing accordingly.

http://thebarnfloor.com/catalog/prod...6#.VjjvYCvpw-4

with more voltage and proper Kv and gearing, you should see better running especially in temps.

Love to see some pics and more info on what you have.

I converted a redcat dunerunner, you can read all about it here: http://www.redcatrampageforum.com/showthread.php?t=9425

For a 30lbs car you need high voltage low current. So I ran 12 or 14s. Good luck.

Thanks for your advice. Both replies agree that I should increase voltage. I can only do 8S on the XL2, but I think my next packs will be 8s.

The kershaw packs are expensive, and I was trying to avoid them. If I have to, I have to. Vant is more realistic. I might try them.

The site won't let me post pics, but It's exactly like the system that Kershaw now sells for $1200 with the truck included. I bought it before they had that as an option. Mine looks a LOT more scratched up from mowing through cat-tails and 2 foot grass and weed meadows. It really kicks ar**.

Update is, I charged my packs and now they won't balance. So, in the trash.

Thanks

can you post your full electronics you are using as well as cutoff settings on the ESC?

Kershaw designs is selling 2 packs for that $261 price if I am reading it correctly here:

http://www.kershawdesigns.com/Rampag...Converison.htm

I spoke a bit with Dan last night as he is getting in those new Hobbywing 1/5 escs where hobbywing lists they can be used for heavy 1/5s like the losi 5iveT. Sounds like they will honor there warranty on them for that kind fo usage and they are water proof so the Rampage may be back on the table again for me lol.

Funny, just traded one but looking for a "play" vehicle that is electric and big.

If you want I can post the pics, just tell me where they are at if you have them on photobucket or similar.

Castle XL2 esc, I set the lipo cut-off at 3.70/cell. I also turned on punch control to prevent my driveline from becoming twisted metal.
Castle 2028 NOT extreme series.
Traxxas TQi transmitter/receiver - I got used to these in the 90s, and never gave them up.
Stock servos
Generic cap pack for the servos
That's it for electronics.

The XL2 and 2028 give me all the power I think I'd ever want on this thing, and they don't get hot at ALL doing it. I really think the battery setup was my problem. I'll PM you the link to my photobucket.

Alex

yeah its most likely the batteries can't keep up considering what you mentioned.

Just like Cain said, run 8S and get the largest batteries that will fit your chassis. SMC has a 4S 7200mah 60C battery as well, for $79.95.

here are the pics:

http://i1032.photobucket.com/albums/...psmo5nfzal.jpg

http://i1032.photobucket.com/albums/...ps8guwh1or.jpg

http://i1032.photobucket.com/albums/...psawmehjun.jpg

If I recall correctly you are selling this on ebay right?