Mamba Max resetting itself?

[TypeR 126]

I'm having problems with my Mamba Max resetting itself after a couple minutes of running.

My setup is the Mamba with a 5700 motor and a 3S LiMn pack in a CRT .5 running a 14T pinion. The car runs very strong and the motor temps are around 130F, with the ESC about 115F when the problem occurs.

After a couple minutes of running, the ESC will reset itself. The steering remains, but the power/brakes go and then I will hear the re-arming tones. If I continue to drive it will repeat the same cycle every few seconds.

At first I though it may be a heat issue, so I added a fan to the ESC and the motor, but I still get the same results. I don't know if I'm possibly overloading the internal BEC? Any help is appreciated.

[kufman]

What do you have the voltage cutoff set to? Is it on auto?

[Demon-TC3]

yea sounds to me like your LVC is set a bit low.


check it over and make sure u have no damaged cells in your pack.

take care,
Demon

[GSMnow]

What RX are you using? What is your low volt cut set at. What is the capacity and "C" rating of the LiMn pack? Does it cut out when you accelerate, or even just driving steady? What do you have as a steering servo? Is the steering possibly binding to where the servo is fighting most of the time? Are you using mechanical breaks with a second servo? On 11+ volts, the BEC will be workng much harder than at 7.4 volts. Assuming just 1 amp to run the radio gear, you are throwing 2.4 watts of heat at 7.4 volts, but at 11 volts it works out to over 6 watts of heat, over double. Do you have an RX pack you can plug in and see if it fixes the problem? You will need to remove the red wire out of the Mamba Max RX plug. Let us know what you find, I am sure we can figure it out.

[TypeR 126]

Thanks for the suggestions! I will try and run some tests with my other packs to see if I get the same thing. Unfortunately I don't have another 3S pack to test with.

Currently my LVC is set to auto. The behavior begins within a minute, or so, with a fresh charge and the pack itself is brand new. I broke it in according to Apogee's recommendations with my ICE charger and delivered the full 3800 Mah on all 15 cycles, but I suppose it's still possible that the dynamic load of the car is exposing a week cell.

I'm using a Spektrum SR3000 receiver. I can 't remember what my steering servo is off the top of my head, but I think it's a digital Airtronics. I've adjusted the steering end points to prevent any binding. I'm using the Mamba for braking duties, so there's just the one servo. Oddly enough the Mamba tends to reset after I've just accelerated and am coasting down (and trying to apply brakes that are not there!), or just after I've come to a stop. I can try the receiver pack, easily enough. I still have a few laying around from my other Nitro cars.

I'll post more results after my testing.

[TypeR 126]

Good news. It looks like it was the BEC being overstressed (even though it was theoretically within published limits). I ran last night with a separate receiver pack without a single hiccup, for over 10 minutes. The pack still had plenty left in it, but that was more than enough time for my testing.

The only other thing I have plugged into the receiver is a small 30mm fan for the ESC, but it would seem that the combined draw, along with the high average voltage of the pack is too much for the internal BEC.

My personal experience with the LiMn packs is that they deliver a much nicer punch that my other LiPo packs, and the CRT .5 is a little heavier than a standard 1/10 scale car. I'm guessing the tolerances just stack up in this case.

Thanks everyone for the help!

[GSMnow]

Glad to hear that worked for you. I guess you will be looking into the Castle BEC10. The linear BEC works just fine on 2S, but the extra 4 volts from 3S is just putting it on the edge, especially with a fast high torque digital servo. Those things can suck a lot of current, especially steering a heavy 4WD.

[Demon-TC3]

to be honest bud i doubt its the Bec on the esc - sounds to me as a combination of the battery voltage fluctuating under laod and the LVC set too low. with an external BEC there is less strain on the cells and hence you dont get as much of a voltage drop under load.


see if you can set the LVC at 2.8v / cell (or whatever it SHOULD be) and see what happens.


take care,
Demon

[GSMnow]

I am not saying it is not possible, but..
Even a poorly designed linear BEC is only pulling 3 to 5 amps MAX with a very hot servo cranking against it's limits. That is nothing compared to the 50 to 100 amps the motor can suck. In my opinion, if an RX battery fixed the problem I really don't see it being an LVC issue. And the fact it also did it when not accelerating, I also leaned away from the LVC shutting down. I have a Spektrum, and the rX will go into fail safe if the RX power dips AT ALL so the steering locks straight and it goes to coast in my case. On my other car with an old Novak 1X I had to add a good sized capacitor bank because the BEC would dip too low and the RX kept resetting. The green led would go out and I would not have control for about 2 seconds.