NEW - ESC vs ESC

[Elios000]

id love to see more EE videos on other things like he did on the Active Freewheeling

a video on the hows and whys of parallel charging would rock so many people dont understand that its totally safe

[eylau2005]

Sorry Guys to interrupt into this fascinating thread but after reading Tony PFW & AFW outstanding explanation ( thanks to exist beautiful mind) I have a doubt that it will make you certainly thinking (and laughing) that I didn't ' understand anything at all about AFW... but let me try to ask (not having deep EE background I think I've the right to ask for stupid question ) .

I'm a fun of YGE ESC (all my model have them on board)... but at this point I?m wandering why YGE does have a AFW switch (via the programming card you can set it OFF-ON) what is the purpose of that switch?? From Tony explanation I would have concluded that it is useless. so why is it there? and HOW the ESC works when I set it to OFF? WHEN should it be set to OFF?.
Keep in mind I always try to gear my model to have a flat throttle curve on 85/90%.... (not sure if that is correct approach or if I should set it close to 100%? ..yes in effect this is a another doubt I've about ESC Governor?
Pls be patience with me but will thanks a lot for any clarification on this Peter

[velocity90]

I always set it to on and it saves about 7 procent of lipo discharge.

[Seasick78]

Seems to me like his question is - but why would anyone ever want it off? What value would there ever be in that?

[eylau2005]

Exactly.. couldn't post a better question tks

[velocity90]

Because if you have low amp draw you are flying in the limit where it switches on and off and then you should turn it off. You will hear this in the motor.

[Seasick78]

What is to be considered the point of switching? Just listen for it? Any other methods recommended?

[Steve Evans]

Originally Posted by ub3r

This new load cell allows me to:
1) Create and arbitrary function using the function generator, and feed the Function generator (FG) output (voltage reference) into the load-bank.
2) The absorbed current is directly proportional, and linear with input reference voltage, from the FG.
3) Also allow me to plug batteries straight in, and stress test the batteries, into a controlled constant current load.

So far the results are good.

The New Load-bank basically consists of a current-shunt, an op-amp, and a High Power dissipation FETs.

I'd be very interested to hear about (3). I'm rather sceptical about the C ratings on batteries, especially over time. When I get logs like the following (actually 6 short test flights playing with the CGY750 governor stitched together) from a "70C" 3300mAh 6S battery with only 20 flights on it, I start to wonder... This was with a 500M motor, capable of drawing a max of 70A, causing a 1.3V drop on a 6S battery. This suggests nearly 20mOhms internal resistance which I'm guessing isn't very good! With this "70C" battery, what voltage drop should I expect to see when it's providing its rated 231A? I'd have thought this should mean that a fully charged battery (4.2V per cell) shouldn't drop below the nominal 3.7V under such a load. Is that the case?



Steve

[FireNWater]

Steve,

From what I understand, "C-Rating" is just a made up number. I have never seen a standard written anywhere as to what exactly the definition of "1C" is as how it relates to other characteristics of the battery.
.
Yes, I know that 1C = Discharge rate at Battery Capacity in Ah, but that is just one number. Where are the equations that use "C rating" to determine other characteristics of the battery? I don't believe anything exists that defines any other characteristic of the battery as compared to "C rating" - i.e. voltage drop, temperature rise, amperage output.
.
So as long as we keep accepting "C rating" as a way to compare batteries, I will keep telling people that it is just a made-up number. Its like telling people my sub-compact car will go 100 miles per hour (but only downhill with a big tailwind).
.
Perhaps a better number to make "them" publish would be internal resistance at some percentage of max load on the battery. Then we'd have a concrete, defined number that we can use to determine other characteristics of the battery.
.

[urgno]

Originally Posted by Seasick78

What is to be considered the point of switching? Just listen for it? Any other methods recommended?

I read that the point of switching is around 17-20A
that on low rpm 700 (TDR, voodoo) at 12s is enough to do some flight
around 800-900W

[SoftShell]

Re: Message #27 - HV80 burned out during testing.

Sorry to beat on such an old subject. I'm new to this thread.

I was just looking up the characteristics of Electrolytic capacitors, and was surprised at how little ripple current they are rated for. Only something on the order of 0.5 Amp!

When some of the following posts started talking about 80A ripple currents, I wondered how any ESC could survive at all at those current levels.

Here's my thinking, if the power supply, leads and connectors have a very low resistance, then the current demanded by the ESC is instantly available, without any significant voltage drop (hence low ripple currents on the input capacitors).
But, with increasing battery/wiring resistance, you get increasing ripple.

This effect may be aggravated for an ESC with an especially low IR.

I now have to ask, how much did the Internal Resistance of the power-supply contribute to the failure of the HV80's input capacitors.

[Way2evl]

Was there ever a conclusion to all of this testing?

[eylau2005]

and to my questions in post 182.about AFW subject.. ".....From Tony explanation I would have concluded that it is useless. so why is it there? and HOW the ESC works when I set it to OFF? WHEN should it be set to OFF?". TKS

[Way2evl]

Originally Posted by eylau2005

and to my questions in post 182.about AFW subject.. ".....From Tony explanation I would have concluded that it is useless. so why is it there? and HOW the ESC works when I set it to OFF? WHEN should it be set to OFF?". TKS

Post 186 seems to answer your question.

[eylau2005]

no it doesn't..in fact there is a question/doubt in 187 either .. in any case I asked 3 questions and not get any answers.... and that is all in ref to great AFW Tony explanation on how it works when it is ON... but doesn't when is OFF... so why there is a switch? how it works when is OFF and When should be turned off. But for the latter you have to know answer 2 first.. I'm afraid only Tony can shed the light on that Have a good day

[Vovets]

When AFW is OFF FETs produce more heat. The less throttle the more additional heat. In practice one should turn AFW OFF only in case the motor does not run smooth and turning AFW OFF cures that. This is how I understand the subject.

[SoftShell]

Originally Posted by eylau2005

no it doesn't..in fact there is a question/doubt in 187 either .. in any case I asked 3 questions and not get any answers.... and that is all in ref to great AFW Tony explanation on how it works when it is ON... but doesn't when is OFF... so why there is a switch? how it works when is OFF and When should be turned off. But for the latter you have to know answer 2 first.. I'm afraid only Tony can shed the light on that Have a good day

I am not so sure about my power electronics. But let me take a stab (guess) at it.

The AFW FET (transistor) cannot be left turned on continuously during the 'off' part of the PWM duty cycle.
As soon as the free-wheeling current dies down to zero amps - the AFW transistor must be shut off.
Otherwise the low resistance 'short' on the motor winding would cause the motor to act like a brake!

At the low power settings, I imagine the ESC is having trouble turning off the AFW transistor in a timely manner, causing the motor to experience some power robbing 'brake' action (and heating) during every switching cycle.

I imagine this is what Velocity90 meant when he said "You will hear this in the motor." in message #186.

[FR4-Pilot]

I've become a huge fan of AFW. I put a YEP 100A ESC on my Swift 16 and so far have been able to dial down the throttle curve to 60-62.5%, which on a 5S pack is giving me 1000-1150 RPMs. I can then dial the throttle curve up, swap in a 6S pack (without changing any pinions) and get 2000 RPM, along with everything in between. This is truly versatile.

On my last flight with a 5S pack I got a 10 minute flight with a 62.5% throttle curve at around 1000 RPM. Nothing gets hot Which is just awesome ! With the exact same settings and a 6S pack it puts me at 1200-1350, also capable of 10min flights. Everything comes down cool - unbelievable. I'm at around 250W with 11-12A, for a 6 Lb. heli.

[seanmichnowski]

Hi guys, first post here! Thanks for all this wonderful info. I was thinking about making my own custom, high-current esc with FETs from DigiKey, etc.

In a previous post, it was mentioned that all of castle's ice2 hv ESC's share a common control board, and the only difference was the FET board (number of them/size of capacitors).

So I'm seeking your advice... what if I purchase the ice2 hv 40A, and make my own FET board to connect to the castle control board? This way, I could make any current rating I want.

I assume the signals going through the inter-board connector are the 6 phase control signals plus 3 voltage sense signals. I'm not sure if the FET drivers lie in the power board or the control board, but I would wind up probably giving each FET its own driver, and fanning out the logic-level control signal to all of them. Maybe through a buffer or something. I assume I should purchase the same FETs used by castle, or at least ones with the same switching time.

Does anyone have experience in doing a similar project? I tried searching around, but couldn't find anyone who hacked their ESC. I'm not looking to beat castle or make a better ESC, just want a fun project. Think its possible? Thanks guys!
--Sean

[JKos]

Sean,
What you want to do has definitely been done. I've seen a few examples around the web. Keep searching, it's out there somewhere.

The ESC used here, for example: http://m.rc.runryder.com/helicopter/t729955p1/

- John