I have something interesting to report!

I finally got my DPR back and put it on my BL X1CR to check what kind of numbers it pushes. I downloaded the data off it now and have been scratching my head trying to figure out why its current readings are so whacked.

The current graph starts at 0 when everything is powered up. But after that the graph shoots abnormally high! I'm getting readings of over 90A on a 10S buggy! Then I noticed where the graph settled when the car was stationary (had a few flips). Even though very little current was flowing at that moment, the graph reflects about 26A. Here's the most interesting bit!

I also noticed short spikes below 26A. The largest of those spikes that reached 0A reflects the battery pack being at 42V at the same time. Here's my take on it:

The DPR resets its zero point if the direction of current flow reverses. So when I connected everything up it's 0A point was true zero (ignoring radio load). The moment I braked for the first time, current flowed in the opposite direction back to the battery! The magnitude of the reverse current set a new zero point, and the old zero point effectively becomes a positive value on the graph.

I'll post the graphs shortly. But I feel pretty confident to say that a Kontronik Jazz ESC does recharge the pack under a braking condition! What's more is it seems like it caps the max voltage according to the lipo cell count (it is programmed in lipo mode). What's scary is that this means that my packs had to endure 26A spikes of charge current! Well, I'm not sure what the implications of that are, but they're not overheating or puffing, so I guess time will tell. :)

I would post the graphs here, but unfortunately this forum is graphically challenged. Check them out on my RCG Blog. ;)

I have had a lot of troubles with my dpr logger that the tech guys had no clue how to solve. Transient amperage spikes, voltage abnormalities, and data loss are really common. I am going to get an eagle tree for my next logger. They have a version with 40hz sampling.

Time for mechanical brakes? :angel:

With the discussion of high ESC ripple current and the effect of using lipos that aren't quite up to the task, I was thinking of ways to help with this. What about using an inductor in series with the + battery line?

Yes, the wires would have to be quite large (probably litz wound), would weigh a few ounces, and there may be slight v-drop. But, an inductor is essentially a current storage device (via the magnetic flux), much like a capacitor is a voltage storage device. And an inductor opposes a change in current flow. So, the inductor will ramp-up/down current flow during high/low changes in current. Wouldn't thins help to reduce ripple current and voltage spikes getting to the battery? And since the ESC is constantly providing somewhat of a load (even when not driving a motor), inductor kickback should be minimal. Thoughts?

Why not just capacitors? I'll admit I haven't yet studied inductors much, but capacitors still seem more logical to me. As you stated an inductor in series with the positive rail between the battery and ESC will require some hefty wiring, and that alone would cost more than I'd care to spend (due to wrapping of the thick or high-strand count wires over the core). In another post somewhere you mentioned that it's difficult to get extra capacitors close enough to where they need to be on the MMM, but what about modifying the case to allow additional wires/capacitors, sized/spec'd appropriately to handle excessive ripple current?

Yes, caps can help, but a good combo of both may be better. I don't want to figure out the math of it right now until someone a little more knowledgeable on the topic can chime in. I'm sure it's been thought of at some point, just thinking out loud really.

what exactly IS the problem? is it the internal resistance of the batteries that gets worse on a high load?

An inductor would be adding too much resistance.

What is the exact problem? if lipo's are not up the task, perhaps the voltage ripple kills the esc; in that case it might be an idea of adding these diodes that short above a certain voltage. put these between the 3 motorwires and it would prevent an overvoltage to occur.

Is it Zener Diodes you are thinking of Serum?

About the inductor, it's kinda hard to say what that would do on an ESC; but wouldn't a large cap bank like the one I have make more sense? Looking at my eagletree results from last year when I have my monster quark running, and comparing that to the replacement quark, I have discovered that the voltage drop at a given current level is definitely less. This could possibly be an error in the eagletree, but I don't really know. Just my two cents.

No, No, No...

Only capacitors, and just a good bank of ultarcaps will convert low current LiPo into short-term (need to define voltage drop and timeframe, formulas available) high current killer power pack.

Inductor can be in motor leads, but not in power. Ripple current covered by capacitors, voltage drop can be covered by ultracaps and zeners (in one half).

Is it possible to buy Ultracaps somewhere? How expensive they are?

Artur,

I'm going to get the caps I told you about. I have to try it out and see where they stand.

Yeah, kinda figured, but doesn't hurt to ask...

Maxwell Technologies has some RC size ultra caps that would work wonderful for high powered BL setups. They are C size cells, 2.5v/120Farads IIRC.

I will get link in next post...

Yes, www.maxwell.com, www.enerland.com and www.maxfarad.com. The ones I'll be gatting are he size of a button cell just a bit bigger then the ones found in digital watches.

Anybody have a link to some Low-ESR caps that are similar to what is on the Mamba Max ESC? I was thinking about adding a cap bank to help it run a little cooler (only gets to around 120F with a fan and a medusa 4800 kv pulling some hefty gearing). I would like it to run even better though... It's starting to get into the low 90's down here in Florida, so I'd like some extra cooling insurance.

Also, I should solder them closest to the power leads, yes?

You can look around www.newark.com, www.mouser.com and www.digi-key.com.

Edit: I got some Axial type capacitors that I'll be adding them up. They are the same width as most of the ESC I have and I'll probably hook it up to my Scorpion controller. They are Nichicon 50V 1000uF each. Should make a good bang when connecting :lol:.

Thanks lutach. Could I just pluck some off of a PCB I have laying around (say...from a computer's mobo?).

I don't the the leads will be long enough, plus you won't know how many hours they've been working.

Unfortunately caps from mobo's are lower voltage (~5v on mobo's)... and lot's of the time they are only lower rated 85C rated, which usually means not so low-esr.

Go on ebay and type in Nichicon low-esr 35v caps, and choose between 250uF and 500uF, they are usually the most effective for space/performance wise.

Lutach, a button size ultra-cap will have a relatively high esr, even compared to a lipo pack. You might want to look for something larger... I have found the Maxwell's to be the all around best for this.


http://www.maxwell.com/ultracapacito...l/bcap0120.asp These are the Maxwell ultra caps that I would use... 120F, 2.5V each (You will want +20% pack voltage handling), and are ~$15 each.

Thanks guys for the info. I'll have a look around on the 'net.

Yes, Artur said the same thing, but I see that some companies are using Capxx capacitors and they have higher esr then the ones I looked at. I can get the ultra caps fairly cheap, but I want to see what these other high capacity caps can do and they are much cheaper and comes in higher voltage.

Edit: I have also spoken with a company that makes a hybrid, low esr, high voltage and high capacity cap, but the price on those are up there.

Ok, I did some rummaging, and found my fried HV maxx controller, so I just stole the cap off of there. It's a 2700uf 25v low ESR (105 C) cap, so I'm guessing that should definitely be a good little cap to install on the mamba max, no? My only issue....I need a hotter iron. The traces on the PCB, the heatsink, and the wire leads themselves suck up WAY too much heat to get anything done. So either I need to use the 100 watt weller soldering gun my dad has, or connect the cap on the actual battery leads.

Any suggestions?

Hello,

Just to add my stone to this thread, most microchip/onboard controler manufacturer provide some thick documentation about there chips.

The most used in inexpensive BL ESC is the infamous Atmel Mega8, Acccording Mr del castillo (need quote) they didn't use it because they need more processing power to drive some motors and add more features.

http://www.atmel.com/dyn/resources/p...ts/doc8012.pdf

Sorry it seem that i can't edit my previous post anymore

http://pix.nofrag.com/8/1/0/bf124943...35eb817185.jpg

Mister-T,

Good info. Do you follow the BLDC thread in rcgroups? Some of the guys there have said that the Atmel MCUs do a better job in brushless application. That's why a lot of companies use the ATMEGA8 and ATMEGA16. Most of my controllers that have those will drive all motors that I have very smooth. They might not have all the memory like the Silicon Labs one, but some manufacturer can stuff a lot of info in them.

I have seen some interesting stuff with STm microcontroller, they do have there own patented way to detect back EFM, so it can pretty much always start the motor even under load (compressor application they said)

I think some of my Kontroniks have a STM MCU, it's not really clear. Maybe tht's why they have such an incredible start up. I haven't been able to get any of my Jazz controllers to cog on start up.

I wonder what CC used on the MMM?

Rubycon (http://www.newark.com/39K2343/passiv...-35ZLH390M8X20). The picture in the link is only for your reference.

http://www.rc-monster.com/forum/showthread.php?t=11912

I think he was asking about the microcontroler, not the capacitor ;)

I must've been day dreaming about caps :rofl:. Castle uses Silicon Labs MCU.

They are not as talkative as STM or Atmel :/

http://www.silabs.com/tgwWebApp/publ...motor_bldc.htm
http://www.silabs.com/tgwWebApp/publ...LDC_MTR_RD.htm

This one give some good info

http://www.silabs.com/public/documen...r/en/AN208.pdf

Have you checked the links under my signature?

The best caps for our ESC's in current form factor would be Panasonic FM-type. Check datasheet for lead spacing and dimensions, look for lowest ESR and voltage at least 25% higher than you battery Voltage.

I like Atmel's and there is nothing special about finding rotor position without spinning, but tricky :) Solutions available but not every programmer now how to do math (or willing to do math...) on micro without floating point support...

Couldn't you just send a small pulse to two or three coils to sense position when stopped? I noticed that the quark ESC would always make an outrunner hum a bit when idle. It also started up outrunner like a champ with no audible noise.

I think it was sending very small current to sense the BEMF to determine rotor position. It would be cool to see a programmer stuff something like a memory that actually remembers where the rotor was at the time it stopped and when you give it throttle, it would be smooth. Every day that goes by, I regret more and more not getting the electronic engineering class (that also included programming) when I had the chance. I've heard from many places that makes ESC that a HV controller would need to have sensors to accurately know where the rotor is at all times and this is where I hope and wish Aveox makes a comeback. It was one of only a handful of companies that had big 5mm shafted 4 pole sensored motors.