Baffled by electrics

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miket

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Hi all, I have recently ventured into electrics from Nitro and I have a traxxas emaxx. It is the brushed version with the two Titan brushed motors and running two nmh 7.4v batteries. The truck is awesome and at some time in the future I want to upgrade to brushless, but in the meantime I purchased two Lipo 2s batteries. They are zippy 5200 30c . With the nmh batteries in it runs as it should, but when I put in the lipos, sudden opening if the throttle from closed just makes the car stutter and stop completely. I have noticed that the red light on the esc changes to green as it stops and disconnects the power. If I feed the throttle in slowly and then increase, it shoots off as normal. The same occurs in reverse. Has anyone got an explanation why this might be happening. Any help would be most appreciated.
 
Its a red coloured esc. Says model 3104.
 
Lipo's have sometimes been used on the orange/red esc using an LVA. The ones that use lipos, have commonly run into thermal issues on it. I think this is what's happening.
It was designed for 2x6cell nimh. roughly the same voltage as 2x2s lipo. But went into thermal mode using lipo
 
Sorry dude but a 6 cell nimh charged is 8.4V - 9V in series 16.8V - 18V
2s lipo charged 8.4V, I would say that's close to a 6cell nimh. I'm sure google would show lipos being used on the evx.
Your comparing nominal voltage of nimh to charged lipo.


The description about only using 6cell nimh was before lipo was thought of and not to use 7cell nimh. which is 9.8V-10.5V. Although some did use 7cell nimh
 
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No worries dude, I blame the cold weather. We don't get much hot weather here.
If it is a voltage thing, I can blame that. :)
I would call it red esc, but it's more known as the orange esc.
 
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Thanks for all that, but what was the final thoughts, you lost me after the 7 cell nmh. It seems to me that the surge of power from a sudden throttle is having some effect on voltage?? Current?? If I feed the throttle in carefully it goes ok. Bloody hell I only had to think of % nitro before and rich or lean. I've a lot to learn!!
 
The Voltage of 6cell nimh and lipo are similar, The effects of using lipo on the quite old esc is a type of thermal shut down, When you pull the trigger from stand still the voltage pushes the current to the motors to get them started, Once turning the magnetic fields make the motor draw the current.
The esc is either going into this thermal situation, or the motors are old, they're not the best of motors/or geared high drawing more current overheating the esc.
People have used lipo's on this esc with lva, The first thing that normally goes is the motors.
If you lived in uk you could have my old titans.

Fuel % is all foreign to me, I'd just pour in anything available. :)
 
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Thanks trax. It must be the esc cos the motors have hardly been used. I bought the truck off a guy who kept it as a shelf queen. It was virtually grand new. Strange thing is that it runs fine on my other lipos which are turnigy 25c 2200mah. Looks like I go back to those or to the nmh batteries. I suppose I could change the esc but they are so expensive in the uk!!. Anyway, thanks all. mike
 
The old esc only has a 5V bec. The servos like 6V, on ebay there is a few chop shops that sells parts haven't looked for a while. Once in a while an evx2 pops up, normally go for round about 40 quid. Its a much better esc than the old one, but there is many revisions and some are funny with voltage. Some can use a 5s configuration and some can only use 4s input voltage. Mine works upto 20V, but not the 5s voltage. Unless I work the servos for a few minutes to get the voltage down then it works.
My next lipos are going to be the new high voltage cells when they are in stock if the specs are confirmed
 

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