A123 packs are recommended because of their low resistance (not so much their ability to put out power, but rather their ability to absorb it). They allow power to be "put back" into them very quickly(ie:they can be charged in about 10 minutes or so with the A123 charger). This ability to absorb the energy back is what makes them "Castle Approved". The energy doesn't "get caught" in the ESC because the path to the batteries offers low resistance.

Hmmmm...... I know I saw on another brushless esc manufactures website that a123 cells have a comparatively high internal resistance. They did not want a123 cells being used with their esc's. I'll try and find a link.

Hmmmm, I'm interested in who this manufacturer is.

Found it. This pdf applies to this thread. Page three is where they talk about the a123 cells. http://mgm-compro.com/pdf/en-motor-braking-050409-g.pdf

Ah, now I remember.

"In both cases, it is therefore enough to intensively brake only once and the controller can be easily and quickly damaged,
basically after few meters‘ ride.

The paradox is that the better controller you use (the more quality FETs and PCBs, or the more FETs and thicker copper layers it
has on pcbs, that is smaller resistances of FETs and connections it has), the worse the situation. The motor, working as a generator
during braking, causes more energy (current) to flow to the battery. Thus higher voltages are caught on the resistances of the
conductors (Rconductor) and inner resistance of the battery (Rbattery) and therefore higher voltage will also be on the input of the
controller (UCONTROLLER). That means, the destruction of the controller is more likely to occur when there is not enough reserve in its
voltage dimensioning."

Patrick,

I would like your input on what Mr. Grisa mentioned in the PDF file provided by lydiasdad. You have mentioned that you use a lot of copper on your ESCs which I think is good, but Mr. Grisa thinks otherwise form what I gathered.

Lutach,

Mr. Grisa didn't say it was bad to use alot of copper in an ESC. He just said that it made it worse when using higher resistive batteries when running at the voltage limit of the ESC.

During braking with a high quality ESC(low resistant), more current flows back to the battery. But with a high resistant battery and low quality connectors, the back current can't be absorbed well/fast enough. Thus you get a more voltage accross the input of the ESC( taller voltage spike at brakes), than as you would with the use of a higher quality battery pack. With the lower quality batt pack, the ESC will freak out and say "forget this shiat" and let the magic smoke loose.

Dunno if I explained it well enough.

All this talk and no one has stated the obvious:

1) We need ideal batteries; a pure voltage source with no internal resistance and infinite current capability

2) We need ESCs with 100% efficiency. FETs need to have have infinite slew rates, 0 rdson, infinite gate resistance, infinite frequency response. All the copper has 0 resistance.

2) Motors are 100% efficient; no copper losses and 100% of all magnetic flux is utilized. And, the rotor would be made of superconductors since they repel magentic field, so no need for magnets.

:smile:

Cool, I will pay for all of this technology for everyone on RCM with my money tree in the backyard. Right now the 20 dollar bills are in bloom but in late fall the 100's sprout! It's a nice early winter harvest.

So.... where exactly in Houston do you live? :whistle:

Not too far from me it seems. The last storm we had blew some bills over into my back yard.

Ok, so I got this thing inside my head that's driving me nuts. I have a M.Troniks ESC (Sorry Patrick, I know this is Castle's section) the truck one and it came with 3 diodes to add to each phase and then it went to the negative battery connector. Now what are they really for?

http://i206.photobucket.com/albums/b...p/DSCF2201.jpg (Thanks linc for the pic)

This is what I found in the Mtroniks manual. I believe the newer ESC's have them built in.

Mtroniks offer a simply installed power booster diode pack, which you can install to your controller and this will

solve overheating problems in almost all cases.

From the way they are hooked up (cathode to ground), they look like they would clamp the EMF spikes to whatever they are rated for. I would assume they are similar to the TVS devices in operation, except on the motor wires instead of the power input. Another possibility is to add/supplement the built-in diodes in the FETs (older FETs may not have the diode integrated, I dunno).

Makes me wonder as well. Novak, Quark manuals says never to use schottky diodes with their brushless controllers. But Mtroniks always had them. Maybe old school Brushless ESC users can chime in.

They were Schottky diodes iirc for clamping I thought, but IDK for sure. Still have my Mtronics around actually.

Edit: sry for the simulaneous posting

So basically that would prevent all the current and/or voltage from rushing back to the battery per say?

seems like it. But the ESC functions without them, correct?

Yeah, they basically shunt any voltage in excess to their rating to ground, thereby clamping the voltage to a more manageable level. Protects the FETs and caps from overvoltage, not to mention the batteries. That is IF they are that kind of diode. Like I said before, they could also be intended to function as the "body diode" found in FETs (but basically do the same kind of thing).

well i think that we should all get over this!!
taken too long and no one knows a true answer yet!!!
leave it alone, go try it in practice and see what happens!!
nerds vs nerds dosent work guys :lol:

Very nice discussion guys! Some of you are definently more in the know about circuitry design then I ever was, hence why I had to drop out of electronics design in college, my brain hurted :lol:

They have an electrical class there? I thought all ya had was painting, basket weaving, and wool fashion design.....:lol:
[IMG]http://i244.photobucket.com/albums/gg33/jjt4806/msu.jpg[/IMG]

Don't forget deer skinning 101

Nah, we had that at Montana State - comparatively we were the redneck school - U of M is the tree hugger community.

Smart ass.... :whip:

Yuk....yuk....! I've got another pic for ya, but they have Photobucket blocked at work.....I'll post it up tonight.

Edit....I think I'm gonna save my other pic for Nov 21st...just in case....

This thread (and the others like it) are THE reason I visit this site.

Meaty, is the word that comes to mind......

I'm bumping this because SOME PEOPLE STILL insist on stating that higher pinions = safer ESC's, even with 6S.

Tell them to get a data logger to get a basica idea of how many AMPs various gear ratio will pull. I've done my homework and I have a solid set up.

Or, let them continue down their own path and figure it out the hard way. Maybe after the 12654615th time their ESC thermals (or worse) they'll understand. :rofl:

The problem is that they will burn up ESCs left, right, and center and blame CC for it and go all around the internet trying to sully their reputation. It already happens, but with all the n00bs coming into the market because of these RTRs we're going to be seeing more and more of it because people simply don't understand how it works and they want to go 60 MPH through 3 feet of grass with 8" tall tires and have everything work perfectly.

I agree on the EagleTree, I'd like to see someone running 15T, 20T (stock, I believe), and 25T pinions on 6s and post up good graphs on all 3 to show exactly what gearing does to amp draw. Also post up temperatures and such to show what the increased/decreased load does to temperatures across the board.

Amen to that! All that power and no knowledge/appreciation of how it works is a recipe for disaster.

Yeah I hear what you guys are saying. I was referring to the people who have been told it's not the case but continue to do so.

That should be Castle's and HPI's (even traxxas's) 'line':-

1.noob cooks esc through over gearing/ massive tires/ tall grass etc, send it to castle for repair.
2.castle kindly repairs/ replaces cooked esc, but includes a note to say that excessive gearing in the wrong conditions (tires/ grass etc) will result in further meltdown, will not warrenty the esc if same thing happens again.
3. noob cooks esc again 'cos da manual says 6s + tall gearing am okay', sends it to castle.
4. castle say 'get knotted' because they didnt heed the warning **from the esc & motor manufacturer no less**, forces noob to pay for non-warrenty repair.
5. noob cries to all his mates about paying the repair fee, hopefully warns them about overgearing.

In an ideal world that is....

trouble is..we feel all cool because we know this!!
all traxxas and hpi need to do is say "60mph!!* *under correct conditions and using ONLY 30C 5000mah lipo's"

that'd fix quite a few issues!!
but nooooo..the companies in question, traxxas = speed runs and HPI = high load back flips AND speed runs (and not advertising a gearing change between monuvers)

As they all say, speed and power sells. Too bad they fail to realize how much current is actually needed to push a vehicle at the claimed speeds. It doesn't only come down to using the best lipos. Castle should put some rules out and also call them out to avoid many more failures.

I thought it was sex that sells? They should start displaying scantily clad women on the boxes of their products.

Sex sells but stupidity is always free

I was going to say that....But if you're buying a vehicle, most would go for speed and power. Example: The new Ford car with ECO boost. I don't know where the ECO come in, but the car seems to be fast.

How do you tell if your battery is a good one and how to do track your batteries ability to discharge as they age? Several Lipo chargers can also measure battery resistance. The ones I know of are several Hyperion and NeuEnergy chargers. I am sure there are more that have this feature, I am just not aware of them. Internal resistance is what controls a C-Rating, the lower the internal resistance the faster the battery can discharge before it overheats. A batteries internal resistance (C-Rating) also determines the amount of ripple current the controller will have to deal with. The lower the batteries internal resistance the better the battery. With one of these chargers you can simply plug the battery in and records its resistance. The lower the number, the better the battery. If you track a batteries internal resistance over time you will see its resistance going up as the battery reaches the end of its lifespan.

With a charger that measures internal resistance it is interesting to plug in different packs of the same size and type from the same battery seller and see how different they are. If you do this you will find that the better battery companies have much less variance in their batteries because they QC the cells they use. You can also go through several cheap batteries and separate the good from the bad. Another interesting thing to track by measuring internal resistance is how many good cycles you can get out of specific packs. Again, you will find that the better batteries (except for bleeding edge supper high discharge cells, which typically don't last very long) will last much longer than cheapos. If you then calculate cost per run you will find the more expensive better packs are actually much less expensive in the long run.

The equipment it takes to measure battery internal resistance makes doing it yourself expensive and impractical, but it can be an easy job for a charger. Look for this feature in your next charger.

Bernie