Stock Revo's EVX-2 on fire - RC-Monster Forums

**Stock Revo's EVX-2 on fire -** 11.17.2008, 04:38 PM

I was running stock e-Revo for some months now. Two weeks ago I have bought Lipo's, installed the Novak's LVC and all, and couldn't stop smiling (for 3 runs). The LVC was working fine, and considering it's only titans -the car had much better acceleration than with Nimh's, of course.
Two Days ago - I was at the track (just basing around). After about 10 minutes of bashing - the car stopped moving, steering servos were still responding. I went to see What was wrong:
The titans were warm, but not hot. The Evx-2 - the same.
I disconnected the battery connectors and connected them again - the Evx-2 went on, but only the steering servos were responding.
I thought maybe thats the Novak cutoff that wasn't good - but it seemed O.K. When I "programmed" the cutoff -it acted perfectly (red, green lights and all...).
I tried to disconnect and connect the batteries again - and PUFF! the Evx-2 smoked on me.
When I went home this is What I saw :

Does anybody know what was wrong here? Why did that happen? anyone had similar experience? Do you think it's related to the cutoff at all?
Please Help. I sent the EVX-2 to Traxxas, but do not want it to happen again with the one they will repair for me...

E-Revonut · 11.17.2008, 04:57 PM

I had a similar experience. I still need to call Traxxas. I was using the Novak LVC as well with 2x 2s 6000mah MA packs, ran it a few times no problems. Went to play on a baseball field and within 2 minutes my titans both let out their magical smoke. I'm not sure if the esc is damaged too. I need to call them though as winter is pretty much here and I'd like to be able to play with my REVO all winter.

BrianG · 11.17.2008, 05:40 PM

Which wire burnt? The red or black wire?

I can see something like this happening if the external LVC was hooked to the wrong set of ESC power leads. Generally, the overall ESC battery and throttle cable grounds are common. If you hook the external LVC to the wrong negative battery lead, you are placing the LVC ground at a half the full battery voltage potential and risk burning it out. TBH, if this is the case, I'm surprised it didn't blow sooner unless there is enough resistance in the circuit and wire to limit the current somewhat.

11.17.2008, 05:55 PM

The black one melted Totaly. The others (red and white) seemed o.k to me.
Brian - I made a harness ("keager") and hooked it to the BEC side. I will post pic tomorrow.
Thanks BRIAN. appreciate the help!

BrianG · 11.17.2008, 06:00 PM

That makes sense since if the scenario I posted is true. You are basically shorting the BEC-side battery, but since it is not a direct short (due to some wire/circuit resistances), the wire lasted a while.

The BEC is hooked to the most negative battery pack and is the one the LVC should be hooked to.

I'm not saying this IS true, but sure would explain what happened.

sikeston34m · 11.18.2008, 05:13 AM

The only time I really played with the stock Titans and the EVX was on the very first E maxx that I got. That was a long time ago. These days, the Titans and the EVX come out and usually are quickly sold. Brushless goes in, right from the start.

A Friend of mine purchased the new E maxx back in the summer of this year. He has had alot of trouble with it and has been able to only run it a few times.

He has melted 6 or 8 sets of batteries into smoking piles of goo. After taking it back to the Local Hobby Shop twice, and the motors/ESC being sent back to Traxxas for "testing", he was told it was the batteries he had been using.

He asked if he purchased a set of this guys best Nimh packs, if he would warranty them against melting like all the others. The answer was No.

Meanwhile, it was rumored that Traxxas would not honor warranty issues if Lipo batteries were used with their setup.

4S Lipo is 16.8 volts. I seem to recall seeing that listed as the maximum voltage on the EVX.

He has asked me several times what is going on here.

The original E maxx setup was relatively slow, but reliable. If I remember right, the original setup was:

Motor pinion/ spur gear: 18/66
1st gear ratio: 13/36
diff ratio: 13/37

In the Quest for higher top speed and more advertising bragging rights, the new E maxx/ E Revo setup is this:

Motor pinion/ spur gear: 19/68
Single Speed Ratio: 18/33
Diff ratio: 13/37

Huge Difference in gearing.

My friend demonstrated his truck to me. After about 15 minutes of running, his ESC and Motors were getting HOT. 160 degrees or so, but by this time, the twin 7 cell Nimh packs were melting the shrink off and were sizzling. Several cells were so hot, they were oozing and leaking.

IMO, the Titans/ESC are being pushed to their limit. They are being asked to deliver watts they are not capable of. Starting torque required to pull this type of gearing must be around their "stall torque" with this type of gearing.

I've checked my friend's setup for binding and all of that. I don't see anything wrong.

IMO, a much smaller motor pinion would have to be used to get the kind of reliability the original setup had. Something in the 14-16 tooth range.

What do you guys make of all of this? Experiences?

11.18.2008, 01:31 PM

Quote:

Originally Posted by sikeston34m

The only time I really played with the stock Titans and the EVX was on the very first E maxx that I got. That was a long time ago. These days, the Titans and the EVX come out and usually are quickly sold. Brushless goes in, right from the start.

A Friend of mine purchased the new E maxx back in the summer of this year. He has had alot of trouble with it and has been able to only run it a few times.

He has melted 6 or 8 sets of batteries into smoking piles of goo. After taking it back to the Local Hobby Shop twice, and the motors/ESC being sent back to Traxxas for "testing", he was told it was the batteries he had been using.

He asked if he purchased a set of this guys best Nimh packs, if he would warranty them against melting like all the others. The answer was No.

Meanwhile, it was rumored that Traxxas would not honor warranty issues if Lipo batteries were used with their setup.

4S Lipo is 16.8 volts. I seem to recall seeing that listed as the maximum voltage on the EVX.

He has asked me several times what is going on here.

The original E maxx setup was relatively slow, but reliable. If I remember right, the original setup was:

Motor pinion/ spur gear: 18/66
1st gear ratio: 13/36
diff ratio: 13/37

In the Quest for higher top speed and more advertising bragging rights, the new E maxx/ E Revo setup is this:

Motor pinion/ spur gear: 19/68
Single Speed Ratio: 18/33
Diff ratio: 13/37

Huge Difference in gearing.

My friend demonstrated his truck to me. After about 15 minutes of running, his ESC and Motors were getting HOT. 160 degrees or so, but by this time, the twin 7 cell Nimh packs were melting the shrink off and were sizzling. Several cells were so hot, they were oozing and leaking.

IMO, the Titans/ESC are being pushed to their limit. They are being asked to deliver watts they are not capable of. Starting torque required to pull this type of gearing must be around their "stall torque" with this type of gearing.

I've checked my friend's setup for binding and all of that. I don't see anything wrong.

IMO, a much smaller motor pinion would have to be used to get the kind of reliability the original setup had. Something in the 14-16 tooth range.

What do you guys make of all of this? Experiences?

I don't see the connection between what happend to my esc and all this because:
1. I am using a 17t pinion, and not the 19t (i geared down, so the titans will not get hot).
2. As I said - my esc and my motors were not hot when the car stopped running (just warm)....

pasan · 11.18.2008, 02:01 PM

I do remember reading somewhere that certain types of LVC are not compatible with the EVX 2, but don't don't quote me on that. I'm presently trying to locate the article/post.

E-Revonut · 11.18.2008, 04:41 PM

Quote:

Originally Posted by pasan

I do remember reading somewhere that certain types of LVC are not compatible with the EVX 2, but don't don't quote me on that. I'm presently trying to locate the article/post.

It says on Novak's website that their LVC is not compatible with the blue XL-5, nothing about the EVX-2

sikeston34m · 11.18.2008, 07:00 PM

Quote:

Originally Posted by Billyboy

I don't see the connection between what happend to my esc and all this because:
1. I am using a 17t pinion, and not the 19t (i geared down, so the titans will not get hot).
2. As I said - my esc and my motors were not hot when the car stopped running (just warm)....

Sorry, I wasn't trying to hijack your thread. I thought you might find some useful information in what I had to say.

Did the wire between your LVC and the Receiver melt too?

It's pretty obvious something "went south". It appears the internal BEC circuit of the EVX2 encountered a dead short.

11.19.2008, 02:43 PM

Quote:

Originally Posted by sikeston34m

Sorry, I wasn't trying to hijack your thread. I thought you might find some useful information in what I had to say.

Did the wire between your LVC and the Receiver melt too?

It's pretty obvious something "went south". It appears the internal BEC circuit of the EVX2 encountered a dead short.

Ah, its OK

The wire between the LVC and the receiver hasn't melted. I think there was a problem with the esc (it stopped), and afterwards I might have connected the LVC to the non-BEC side of the esc, and thats what melted down the wire between the esc and the LVC (as seen on the picture).
Any ways - the esc is on its way to Traxxas now. I will update if there's new / special with their analysis...