Bad motor or ESC?
 

Hoping someone may have gone through this to help me out. I am getting back into RC electric off road racing and have been doing some improvements to my dated T4. I recently purchased an SMC 6500 mah 60C lipo pack to give a little more pop to my truck. I have a somewhat dated ESC with a Novak GTB and Extreme Sport 13.5 turn motor. When I run the truck with the old Lipo (Team Orion Platinum 4800 mah, 25C) the truck accelerates and runs fine. With the new battery if I peg the throttle (somewhat quickly) the motor makes a funny sound and runs at about 10% of full speed. However, if I pull the throttle trigger back slowly the truck will accelerate to full speed without any problems. The new pack makes the truck 20% faster if I had to guess.

I tested the SMC battery on my B44 and it ran the car fine with no problems accelerating. I would think this is either a bad ESC or motor. Obviously it is probably time to get new but I am hoping to save some cash and just purchase one or the other. I have checked/double checked all wiring and I don't think it is a connection problem.

Thanks for your help.

Suggestion
 

Try wiring in a capacitor if not already present on the esc if this doesn't work then iam pretty sure its an Esc problem i had a somewhat similar problem with a Trakpower ms-1

Unfortunately there is already one connected to the esc. I guess I don't understand why it works for one battery and not the other?

Try a new sensor lead

Are these both 2S Lipos?

Yes, both 2s lipos. One has much higher current potential.

I see... It sounds like the ESC is backing off with the sudden surge of current. My kit ESC does this when it starts to get pretty hot. For me, adding a fan over a new heatsink helped, perhaps in your case trying getting an updated ESC or retard timing on your motor.

Unfortunately my set up is pretty old (from 2007) so the sensor cable is hard wired into the end of the motor.

The ESC has a fan on it and it does this anytime, whether hot or cold. I think I am going to try a new motor first and then if that doesn't work purchase a newer ESC. The motor is a Novak EX "Sport" model and maybe it doesn't like the amount of current being thrown at it...who knows?? I just know the same battery was hooked up to my B44 with the same model of ESC (Novak GTB) and it works just fine. I guess it is just money and we can't take it all with us when we go!

What kind of battery connectors are you using? Bullets or deans type? Could be a loose connector in the battery itself.

Using a Deans Connector. The same Deans works fine with the Platinum pack and also worked when running my B44....so I don't think it is that.

Yeah, in this case, try a new motor and see if it fixes the problem. :)

Emailing with Charlie over at Novak and he said to try replacing the power capacitor so I have one ordered. Will report back after I get it installed...still thinking I am going to purchase a new motor regardless. Has anyone heard anything good/bad about the new Viper VST Black Edition motors? They seem to be priced very well.

I should've stated more clearly...could be a bad solder connection in the battery case itself.