Another one has let the smoke out
 

Well I had alot of smoke come from under the body today. :013:
It really had me worried. I was thinking my limns.:002: I took a couple pics of it. On the truck and off. Do you think it is a bad esc? :032: :005: Attachment 1175

Attachment 1176

Attachment 1177

Now for the job of dealing with getting it fixed or just get a new one. :mad:1 :mad:1 :007: :007: :002: :002:

Did you change anything from before?

I'm well nervous, just orderd my 2nd one after last smoked, I'm so scared it might happend again. Spent every last penny getting a new one. :(

Are those wires on your motor unisolated Leroy?

It sure appears that way.....

but they don't touch so it is good. I didn't change a thing. I want that long in my play sessioin either. gee The bk is not looking good.

Wow, that sucks. Too bad you can't stuff the smoke back in! :)

Seriously, I always worry about that happening to mine. That's why I get an ESC that will handle at least 50% more current than the motor requires. I took the shrink off my BK 12020 and noticed the FETs are stacked with a layer of PCB in between. Each layer had heatsink grease, but the layers were not closely mated, so the heat on the lowest level is the highest and is the most at risk of thermaling. The little heatsink they do have is only on the very top level.

I think some of the problem with these ESCs (BKs in particular) is the fact they make them as small as possible so the heat is too concentrated, even with a heatsink. I wouldn't mind a bigger unit if they would increase the reliability. Or, even a 2-part ESC; one part for the "brains" and current sensing which would keep the processor and other related components cooler, and another part for the high current output FETs that use larger TO-220 (tab style) devices individually heatsinked so the heat is properly dissipated and replacement is much easier for the normal person. Plus, a 2-part design would isolate the "smoking" part.

Does any one have a suggestion on a new esc? I was thinking the 125b quark. The mgm 24160 looks nice to. It may be a find esc for the 2250 to. :D

I haven't run my Quark 125B yet, but I am much more impressed with the construction and implementation. There are a ton of programming options too, one of which you can set how aggressive the throttle is, since the most current is drawn on takeoff. Stopping power can be set too, which is another high current operation. There is even a battery setting where you set if you have normal or high-perf batteries, presumably so the ESC reduces the current spikes to help protect the batteries (which would therefore help protect the ESC as well I would think). Pretty nice.

Quark looks very durable. It is probably the next one I will consider, that or an MGM.

Seems BK are having a few 9920s pop lately.

i am scared about my 9920 now! Sorry what happened to you leroy! Im getting a quark 125b if i fry this 9920!

There goes another one... Just make sure you let us know how long it takes for BK to service it!

I'd go with the Quark 125. They have offices that can do repairs in Southern California, so you don't even have to send anything overseas! Besides that, I haven't heard of one smoking yet.

Yeah but long time ago i did hear of bks smoking either. The quark is so new it kind of has me worried to get it. I ordered up a 24160 mgm. I figure i can put the 2250 on it later. :D

It is going to head back to mikes tomorrow. So not sure when mike will send it back to them.

just wondering which BK smoked up the BK 12020 or the BK 9920?

The one in the pics is a 9920. I have a 36120 as well. I think this is #3 I have let the smoke out of. One is in germany now getting fixed.

sorry to here the bad news leroy

Sounds like a pattern there. Are they getting hot when in use or something? And I assume there isn't something wrong with the motor (like partially melted winding insulation), or mounting screws too far in? The day mine burns up, I'll cry. Those things are too expensive to blow left and right.

Been there, done that...

4 1/2 times for me... :026: It's a tough hobby sometimes, there just isn't a perfect solution (yet).

They said to me it could take 6 weeks to fix. So I just bought a new one.

Brian, i noticed the exact same thing on the BK's.

mine is even worse, the 2nd 'powerboard' is closer on one side, than on the other. So in fact, it is loose, the thick layer of silicone paste doesn't touch the underside of the heatsink equiped upper powerboard. I am not quite happy with this. I thought about taking it apart, and mounting it right..but i don't know how BK feels for it..

Yeah, mine had that gap as well filled with thermal grease. That stuff is only supposed to fill microscopic imperfections between mating surfaces, not fill gaps. It's thermal conductivity goes WAY down when it is too thick (by "too thick", I mean like 0.1mm). In my case, it looks like the thickness of the motor wire solder joints were keeping the PCB from sitting where it should. I'd try to resolder it as well, but have you ever soldered/desoldered a multilayered board? It sucks. You need quite a bit of heat to keep the traces from sinking too much, but then nearby sensitive components can get too hot.

IMO, I think BK should offer a discount on an exchange program to replace ones like ours with a properly assembled one. It would benefit them in the long run for better customer service and a more reliable product. Already, I've heard a number of people with blown ESCs and for some, it's not the first they've blown...

Yeah, I've got experience with multilayer prints. They are a pita .1 mm of paste already is too much IMO. The less the better..

i don't like that way of constructing either. if they used an aluminum plate to transfer the heat. In my case there is this fat 1-1.8 mm gap, with some silicone stuff just floating, only touching the fetts....

If i see something like that, with that amount of paste, i highly doubt if the person who assembled or did the quality control knew what he/she was doing. It's plain ridiculous.

here, this is what i am talking about..

If they used an aluminum plate between layers, they might as well extend the plates fully out to the sides and attach a heatsink to them.

I still think those surface mount FETs are not the way to go; the plastic casing does not transfer heat that well compared to a metal tab type of device, like a TO-220 case. They seem to try to get around that by paralleling a butt load of FETs together. Then, servicing is a PITA; not too many people have soldering irons that can work with surface mount. I like small, easy to mount ESCs as much as the next guy, but I'd be willing to trade a larger ESC to get something more reliable and solidly built. Leave the light and tiny ESCs for the buggies, planes, helis, and any other small scale vehicle.

Yup, that's about what mine looks like, except they dumped more grease in there...

It is bad, but not as bad as you all think...
Yes, performance goes down, but the higher the temperature of the FET - less current goes through this FET. So, FET's with better heatsinking will do the most job, but overall number of FET's will take care of high current spikes, when they cool.
TO-220 and simular are old design, there are better new gen FET's which offer 10+ times better internal resistance. Sooner or later they will be here as well.

If you have 2 layer PCB with power FET's then assume half of the cold current ratings when temperature of ESC goes up. If you have 3 then 1/3...
Otherwise look for smoke.

Artur

P.S. It is better then no grease at all. And if you compare 0.1 mm of termogrease with plastic case of SOIC package, it won't look so bad.

there are to220's available with low internal resistance as well.

Brian was mentioning the TO220's because of the for him more service friendly point of view. He says it clearly.

It's not a fact that TO220 is an old design, there are still new powerfetts coming out, that i would not use in a smd package.

the better the quality of the blockwave, the less hot the controller will be. the faster the fetts, the better, and the lower the internal resistance the better too.

I was talking about this...

There is always fine line, more amps lower R but higher C

Artur

P.S. It is cheaper to populate board with SOIC then with TO-220-like parts.

Serum is right: I was looking at it from a service perspective. I also like the reduced thermal resistance to heat by heatsinking the metal tab (which conducts heat far better than plastic I'm sure you'll agree). Heatsinking the plastic case does work, it's just not as efficient.

And you are right about FETs: as they heat up, they conduct less (negative temperature coefficient). However, this is more of a circuit design parameter to allow them to be paralleled without one or more "current hogging" as compared to a traditional bipolar transistor. As far as high currents are concerned, FETs can still burn up. Any package type that does not shed it's heat will eventually melt. Some of the problem here is the use of the PCB to act as a heatsink and to thermally couple the layers of FETs together so they run at the same temperature. It's just not enough apparently.

those are not used in the controllers we are talking about at this point.

IR is a nice company.

There is one big problem with small FET's...
As long as we are familiar with FET's behavior under high temperature, there is one component which still acts as old transistor. It is built in diode, which protect FET, but in TO-220 package it is serious diode while in SOIC tiny one and not matched to the rest of the diodes. So when it goes it either short or opens, in first case meltdown in second delayed eventual meltdown.
Solution - serious diodes 6 way H-bridge on the motor leads with output directly to the battery. You will be impressed how much heat you will take from ESC.

Artur

P.S. Good low voltage drop high-current diodes.

Serious diodes indeed! How about simply add a slightly bigger (but much smaller than you'd use on the motor leads) low v-drop diode across the source-drain on each FET? Or, just use bigger (while low Rdson) FETs? :)

There is no reason to add FET's if you cannot control them. (If you can built Power FET's replacement board and re-use existing brains. Then no further questions.) While 6 diodes is not a big broblem, it is like old schottky diode, only in BL configuration you need 6 not one.

Artur

That's kinda what I was thinking; use the brains from a 9920 or something and create an outboard "power board" where all the high current (and heat) is. Keep the surface mount where it should be: low power, noise sensitive devices - and keep the through-hole devices where they should be: high power applications. It's not we're starved for room on a 1/8th-1/10th scale R/C...

About using a schottkey diode: Some ESCs specifically mention to NOT use them or it voids the warranty. I guess this is for people who don't know how to properly select the right device, or how to hook them up.

Brain, I like the idea of this 2-stage controller. Would be nice. And you're right, in our application the extra size would be no big problem.

Yeah, I have to agree on the BKs. Their workmanship is somewhat cheap. With more and more big sensorless ESCs coming out, I foresee a hard future for them.
At least they could have packed them in a case.

Well, with the increasingly stiff competition out there, BK will have to improve their product and/or lower their prices or they will be phased out. Competition is good (for us): It increases product features and preformance while reducing prices. Gotta love it. :)

/\ /\ /\ Not to mention service.. schulze

im suprized schulze is still in buisness with their crappy customer service

Well I can't say nothing about schulze cause that esc is still going. Got that on a truck right now.