Thanks Joe, I wasnt sure what your baseline was for "lower". Got it now. So all of this setup info is based on a 2200kv 1515/1Y on 6s? I would imagine running that same motor on 4s would not require the same battery capability either provided gearing didnt change.


Just to be clear can you confirm this for me...

Then with a 1512/3D (1700kv) shorter lower kv motor in a light 1/8 buggy and conservative gearing (35-40mph) I could run a lipo that isnt quite up to the 75A/125A specs and get away with it without damage to the Monster.

Sorry to be a pain, I just read all the bolony that has been posted the last couple days in this and "other" forums regarding the Monster and lipos that may not be up to the task causing the reported dead MMMs and I want to be clear is all. And hearing it directly from someone at CC is better than all the hearsay floating around at this point.

+1

Joe,
i run a 8T with a neu 1515 1y on my mamba max an external bec, ive been running on my 3s2p 8000 maxxamps pack, gearing around 32-38mph max( ive been haveing no overheating an no problems an can max 20 min mains....
(can i gear up, up on 3s to 45 mph max..ON THE MMM)

can i keep running my 3s8000 pack(if geared under 45mph), or do i need to run my 4s6000, or 5s2p 8000 maxxamps pack???

BTW i always run low settings (never under 30% acclimit usuly 70%, an never run more then 5-low motor timming)my LVC is set at 9.2v for 3s on my mamba max should i change any setting for the MMM?

Whats best for 38-45mph racing (an last 20in mains)?
on the 1515 1y/f in a 1/8th scale truggy(trying to keep the weight down)
3s 8000?
4s 6000?
5s 6000?
(a 5s8000 pack is too heavy)
looking to buy another pack(have 3 allready)
thanks
gary a.

Good NiMhs are capable of that and more, holding reasonable voltage while doing it, just not for long, F5B flyboys were pulling over 300A from NiMhs in 3 second bursts before they switched to LiPos and boat and pylon guys were pulling close to 100A continuous, but at those levels your lucky to get half a dozen decent runs out of a pack before it either significantly drops capacity and voltage or goes pop.

Couldn't that be prevented by installing a diode on the battery leads (unless the MMM uses regen' braking)??? Seems like something that should be done if there is the slightest chance of it happening.

The MMM uses regen braking -- has to, there is too much energy to try to dissipate as heat in the ESC, so the braking energy goes back to the battery.

Besides, the diode would just make the capacitors work HARDER, not less -- the issue comes when the power side impedance is so high that the capacitors have to work really hard to keep the ripple voltage low. When the capacitors have to work hard, they get hot -- if they get too hot they fail.

SO -- no resistors, no diodes, nothing at all in series between the battery and the ESC. The lower the battery to ESC resistance, the better for the ESC, and the cooler the ESC will run.

Thanx!

I see. Thanks for clearing that up. It wouldn't be worth using twice the FETs to handle braking just so people could use cheap batteries! :mdr:

100% correct...I'm one of those pylon guys...100A continuous plus in my F5D's...the batteries get about 10 cycles and then I throw them away. Same for the F5B guys. :)

For "getting away with batteries that handle less than 75A", NO, DO NOT DO THIS. If the controller fails due to ripple current we can't cover it under warranty, and you may lose your batteries in the process. Better to buy expensive, buy once.

friends don't let friends use cheap batteries ;)

I will be using 6s1p A123 cells in my conversion that are rated at 69A continuous and 138A burst. So what you are saying is that unless I aim for silly speeds the lower continous current rating won't matter?

Is there any way to overcome this issue with the ripple current?

The only way I can think of is more capacitance. But it gets physically difficult to mount more so near where they need to go...

Ok this has me curious enough I have to ask. Is this issue with the ripple current actually something new or would this have also been an issue for guys that have been running big BL motors on the Mamba Max if they used under powered batteries?

My guess is that the "hard limits" on battery specs is more a liability thing that prevents the new rc'r from buying an el cheapo pack at the LHS along with his new MM and smoking it the first time out. (And no I don't expect Joe or Patrick to actually comment on this one way or the other)

Hmmm I have just seen your post, will 1p A123 packs work?

Cool, that's what I thought, but needed to be sure. That works for me then. Thank you Brian.

We all knew the modders would get a hold of it eventually! :lol: Let us know how it turns out, lutach!

I ran some ideas by Artur (griffinRU) and he thought it wasn't a good idea, but I'm seeing a some different things out there that looks similar, but mine will be for higher voltage. I even had some companies hold the samples, but I might get them and try it out. I also have another idea that will be absolutely amazing if it works out.

Ok Castle guys, explain to me how guys are killing the internal BEC with "poor batteries".

http://www.rctech.net/forum/showpost...5&postcount=22

As Quoted by RURC on RCTECH.net:

"Castle just called me at 1:10 on Wed the 14 of May. It seems that my thought on magnetic field collapse causing a voltage spike are correct. For the internal BEC problem. Also I have been confirmed that poor batteries are also to blame. As I was told the BEC problem is going to show itself within the first like 10 minutes of usage generally. If you dont have a problem dont send it in, it will be returned to you. The future of this problem will be take care of at Castle. As I understand it there will be a upgraded component installed to prevent this from happening. But like I said if yours is working it should be fine. Again they told me that this problem should show itself within the first 10 minutes."

And why the heck are you guys calling someone that doesn't even have a MMM to explain to them what problems you've seen? I'd really like to know if you have this guy on payroll as a contractor?

Is the default switching frequency higher than the MM? I'm no EE but I think that if you raise the switching frequency you need to either lower the inductance or fit bigger capacitors, you can lower the batteries inductance a little by shortening the ESC-Battery leads and using nice fat cable.

Can't really raise the switching frequency too much for a couple reasons; FETs may not have the slew rate to support higher frequencies, and motor inductance can play a big role as to how effective this would be.

Back-EMF voltage spikes can certainly cause issues with possibly more sensitive components of the BEC. But I would think that as long as these spikes are at or under the 6s-7s limit, it should be fine. So, why not install a transorb, diode, or whatever to clamp the spikes at no higher than say 30v. That would give some headroom for 18 NiMH cells (because they can peak as high as ~1.5v right after a charge), yet shunt potentially damaging spikes to ground protecting the BEC circuits.

Makes me think Castle should have just made the MMM an Opto ESC, or put a circuit based off the typical LM2596 IC (which has a 40v and 3A rating)....

DITTO THAT RURC guy is full of Crap, he thinks hes GOD ....
he said hes been into 1/8th scale brushless for over 10 or 15year:lol:
(when we all know 1/8th scale brushless just sarted a few years ago, an just started to cartch on last year)

he thinks he knows everything, AND KEEPS SAYING TO PEOPLE U NEED BETTER LIPOS one that can handle 200amps cont. he saying thats EVERYONES problem for the MMM BLOWING UP(cus the esc need 200amps cont. any battery less will KILL THE ESC):oops::lol::lol:



i dont comet to this guy i just ignore him.
HE REALLY MADE A MESS OF THE BIG THREAD AT RCTECH.COM

(ive been on that thread for almost a year/since i built my electric 8T , its been the best thread but the past few days he made junk of it... i hope he stops his BS cus that thread isc the most informitive for Brushless 1/8th cale conversions):yipi:

He will. I like how he's ignoring me there :lol:. (300A Schulze, I can't get that out of my head).

Do the other people at that forum know he's full of BS? It would suck if people go out and buy lipos capable of 200A just on his word... unless of course he's the one selling them!

I can understand lesser lipos, having higher resistance, allow higher ripple currents to get to the BEC. But, that just means the lipos were poorly chosen for the application to begin with even if the BEC survives. But to say your lipos need to be capable of whatever the ESC is capable of in a blanket statement is just plain ridiculous. Of course, it won't hurt to do that, but it's just not needed in all but the most severe setups. And since the MMM can really handle bursts well over 200A, does that mean the batteries do too? Without reading mr RURC's posts, it sounds like he knows just enough to sound knowledgable and is convincing others as well. Sounds like Mr Patrick should go over there and set this guy straight...

Again, just give us an Opto MMM and be done with the whole BEC thing.

i seen that u asked him like 3time.....
can i see pics of ur 300A sesc?:whip::lol:

he screewd a nice info thread now well have 5-10pages(hope not more) of crapolla:diablo::diablo::diablo:

Brian, I was trying to suggest that lowering its frequency may decrease its reliance on low induction batteries.

yeah in a post he said only to buy this one brand(forgot)
i think he works for them...:yes:

WELL, nice of everyone to keep everybody else honest. :)


HERE IS THE STATUS of our investigation.

1. It seems to be an infant mortality problem with the switcher control chip, a National Semiconductor LM3485
2. There is already a TVS (transient voltage suppressor) on the circuit that feeds the LM3485 -- so it may NOT be a voltage spike related failure (28V TVS on LM3485 power line, LM3485 part is rated to 36V operational,) but we are not ruling out the possibility at this time.

We are working with National Semiconductor to determine the cause of the failures. It seems that making a couple minor changes to the circuit make everything work fine -- but we haven't determined the cause of the failures yet.

Patrick

So Patrick,

Can we use a resistor on the battery to prevent the big spark with 6s setups? Plug in neg, plug in resistor to charge caps, then plug in main positive.

That's waayyy over my head lol, but I know Castle can and will make it right. Does that mean that it is a problem with all of the ESCs sold so far?

It might just be some faulty units. I see that a lot in the electronic industry. Your failure rate is for a new product is not bad at all. Big electronic companies would love to see that kind of failure rate for their new designs.

Thanks for the information Patrick. I just have a hard time swallowing information from someone other than those who actually work at Castle. It's one thing for someone to speculate upon the failures, but it's entirely another for one to dissemenate information about failures from Castle as a 2nd hand source. If indeed someone at Castle is speaking with RURC regarding these failures, you guys should keep an eye on how your PR looks with someone like him speaking like he works for you. However, if he's just some crackpot trying to solve the world's problems, then you guys really should make it known that he is not affiliated with your company because he's really not giving anyone warm fuzzies about the whole situation.

Could it be the LM3485 is really sensitive to ANY spike over 36v and the TVS isn't responding quickly enough to prevent the spikes?

Another possibility (I'm reaching here); could the high voltage and high currents on the motor leads be inducing a voltage somewhere in the BEC circuitry where it is "unhealthy"? I wouldn't think that the chip would be that touchy.

I think it's rather obvious the guy has no connections with CC. I have run across his posts/rants/hallucinations many times reading on forums and usually choose to ignore him. I get real suspicious when people choose to ignore questions they can't answer. I find it rather impressive Patrick and Joe both respond to us on this forum rather rapidly all things considered and would only take there words in these matters and ignore the others.

Diddo he is repeating it today almost word for word.:diablo:

Cound it also just be an infant mortality problem of the LM3485 and nothing more? So some of the units will just die in the first 10 minutes of use...The rest will work just fine for ever.....?

Has anyone heard of one running longer than 10 minutes and then stopping?

I am just thinking out loud here.....

Yep -- that's what it looks like. If it works OK for more than about 20 minutes or so, it doesn't seem to have a problem after that.

Patrick

Are you going to do a recall on the current Monster Mamba Max's and hold off the sale of anymore until you locate & fix the problems?

I mean it wouldn't be fair to someone like myself who has to wait a couple of weeks for international shipping to receive your product only to have it fail within the first 20 minutes, wait a month to get a replacement only to have the same thing happen again.

We have shipping hold right now, pending final determination of the issue.

Please note that this is (so far) a MINOR issue -- we have had 6 failures total out of 1000 pieces shipped.

yes. im from australia, and i just hope that mine works... international shipping isnt very nice... costs a bit too!

Patrick, any answer for this?

No problem,

Use about 50-500 ohms or so (value isn't that important), 1 watt minimum, surge rated resistor.


You will lose that "MANLY" pop when you plug in the battery though... it's very cool on the SHV with 20S and 4000+ microfarads of capacitance... sounds like a gun going off... (We added an inrush current limiter circuit on the SHV, 'cause connectors would die in about 3-4 plugins...)