Argument thread: Low specc batteries don't kill ESC's. Or do they?

[pinkpanda3310]

Originally Posted by slimthelineman

the motor will take all thats available unless something stops it, the esc. if the power is not there to be taken from the battery the motor will fry anything in its path in an attempt to get what it wants, usually the esc.

That makes sense to me. I do understand the esc is just a gate (or series of gates). But what if the power is not there to be had, ie;crappy battery?

[T-birdJunkie]

Then the ESC does not see the current.

If the battery can't supply it, etc etc.

If you open a fire hydrant, and there's only 15 psi at the hydrant, does the hydrant explode?

[pinkpanda3310]

So the only way sub-par batteries can break the esc is through ripple and over voltage?

[slimthelineman]

Originally Posted by T-birdJunkie

Then the ESC does not see the current.

If the battery can't supply it, etc etc.

If you open a fire hydrant, and there's only 15 psi at the hydrant, does the hydrant explode?

water is not electricity and is bound by completely different laws, that said using your analagy you forgot load. What if there was something on the other end that wanted 115 psi. Something will give. Again speedos don't push power that is why the are not rated as maxiumum output only max current it can pass on.

[josh9mille]

Freeze....after reading some of your posts over on that thread on RCU it seems you have anger issues. I now see why people get fed up with you, and I also see how you have been banned from multiple forums. Maybe you should take a chill pill and quit starting drama. It is rediculous how childish you act when things do not go your way. Telling people to "fu** off a**hole" just because they do not agree with you is really messed up of you! End of rant :)

[T-birdJunkie]

Originally Posted by slimthelineman

water is not electricity and is bound by completely different laws, that said using your analagy you forgot load. What if there was something on the other end that wanted 115 psi. Something will give. Again speedos don't push power that is why the are not rated as maxiumum output only max current it can pass on.

OK...

so let's say we have a pumper truck hooked up to the fire hydrant.

What happens then?

[lincpimp]

Not addressed here but really basic is heat.

Load on the motor will dictate its draw from the batteries. If you gear a motor to pull 100wats, that is what it does. So if you have 100 volts you only need 10amps. And likely the wires in the system will be rated for that 10amp draw. So will other components of the esc, connectors, etc. So lets say your battery cannot provide the required voltage and it starts dropping, well the load is still there so the amps spike, in turn dropping the voltage more, causing more amp spikes, a viscious circle if you will.

Some of us here used to run nimhs, voltage drop and amps spikes were pretty common, as nimhs had a hard time keeping up with brushless, and that is why you would see alot of 30cell series nimh setups, as higher voltage lowers amp draw on a fixed load.

So crappy batts will drop voltage under load, and if the load is enough it will cause higher amp draws, which casues everything to heat up and can lead to equipment failure. Usually the esc goes first, but I have seen solder joints melt, motor windings short, and batteries go poof before the esc lets go. In fact i had a really stout MM back in the old days that together with a 7xl killed many a maxamps pack, and did some damage to a few nimh packs with a 7s motor.

Subpar batts are a problem, kinda like using bad gas in your car, that can cause issues too.

[suicideneil]

OK...

so let's say we have a pumper truck hooked up to the fire hydrant.

We arent talking about water, the analogy simply doesnt work when you start getting into specifics or trying to blur the two subjects.

Voltage will drop when when current rises, that is the key thing to remember about batteries, so buy batts that can supply sufficient current before they become over-worked. The MMM system has been observed to pull peaks in excess of 120 amps, so lipos that can provide a maximum continous current of 120amps are recommended; they will however only be supplying about 20-40amps continously in reality, with 120-130amp peaks lasting mere milli seconds..

[T-birdJunkie]

So you're saying water pressure does not drop when something pulling said water through a pressurized system?

Sorry, but in this analogy:

Motor:pumper truck::ESC:hydrant::water supply for hydrant:battery

Electricity, for the most part, works like water, guys.

[PBO]

Originally Posted by T-birdJunkie

Electricity, for the most part, works like water, guys.

It's too basic an analogy

You could always adapt an RC to run on pressurised water...then the analogy is perfect. Electricity is far more complex than water & can't be simplified into hydraulic pressure - sorry just doesn't work

[pinkpanda3310]

Originally Posted by lincpimp

So lets say your battery cannot provide the required voltage and it starts dropping, well the load is still there so the amps spike, in turn dropping the voltage more, causing more amp spikes, a viscious circle if you will.

That was my understanding. I was getting a little confused though Thanks for posting Linc.

[Bondonutz]

+1
I have to honestly say I felt confident that this thread was a super complete waste of time, after it's all said and done and especially James Posted I've come to a little better understanding about these failures. I knew Batterys could def be a culprit but The Pimple made it easier for me to grasp how and why.

[T-birdJunkie]

Originally Posted by PBO

It's too basic an analogy

You could always adapt an RC to run on pressurised water...then the analogy is perfect. Electricity is far more complex than water & can't be simplified into hydraulic pressure - sorry just doesn't work

Electricity is not that complex. It's electrons flowing one way through a system. hydraulic flow is really no different than electrical flow. If you really wanted to, you could build a 3 phase hydraulic stator motor and a system to properly feed it.

If you don't understand the analogy because you don't understand fluid dynamics, that's fine. Don't pretend electricity is more complex than fluid flow, though.

The point is, if the battery can't supply the amperage, then the battery can't supply the amperage. People post a LOT about "ripple current" and simply accept it as fact without understanding it (kind of like how people assume fluid dynamics and electrical flow are different), yet nobody has offered a proper explanation.

From how ThunderbirdJunkie understands it, ripple current is from a battery not being able to supply the drawn current, then suddenly supplies it, and stops, and continues that cycle.

Is this accurate?

[Arct1k]

No... That is not correct...

[Arct1k]

briang

Originally Posted by BrianG

Oh boy. This can get really technical, but here is a simple explanation:

FETs are Field Effect Transistors, and there are many of them paralleled in an ESC. There will always be a multiple of 6 (one for the + rail, one for the - rail, for each phase). The on/off cycles refer to the pulse-width modulation signals fed to the ESC. Longer on pulses results in the motor seeing more average voltage, shorter pulses results in less average voltage getting to the motor.

ESCs smoke from over voltage, being forced to pass excessive current (like when overgeared), or excessive current ripple is present (from low quality batteries), and several other reasons.