540 6S + 3 cell Lipo? - RC-Monster Forums

Tom F · 12:01 PM

Well, my new pack came in a couple of days ago (Hooray!)

Got me a Kokam 4800 3S Pack, been told they hold a higher voltage under load than the Flightpower cells which wer ethe other ones i was looking at.

My main intention was to run this on a Mamba Max 4600...which i haven't yet been able to afford yet, so i'm going to try it on my current motors when my ESC (Mamba Max) gets here, which should be any day now.

I'm after silly speed...and until i can afford a second Apogee 2 cell 3800 pack (to run in series with my current one...), I'm thinking the 540 6S on my 3S Kokam pack will be the best route, assuming it will handle it?

The RPM limit of these things is 65k i thought (unloaded i will be over that - but in-car it should be lower)...I'm gearing low to help tame the current draw, so that coupled with low timing and it should be ok, right?

Just want to check before i try it...if at all possible I want to avoid burning a brand new ESC or grenading the rotor :)

Cheers

- Tom

Edit: This is in my XXXS G+ which will soon be on nice floaty new bearings :)

skellyo · 11.17.2006, 03:41 PM

I believe the Feigao RPM limit is 50K, not 65K.

aqwut · 11.17.2006, 03:51 PM

I think if you upgrade to the boca bearings their limit would be around 70K...
that's what offshore hobbies said... don't know if it's true or not

Tom F · 11.17.2006, 04:23 PM

Ahh, so it's a function of the bearings rather than the rotor?

That certainly makes it cheaper...

Anyone know how to get the bearings out of a Feigao 540 can? :013:

SpEEdyBL · 11.19.2006, 05:37 PM

The bearings aren't the problem. Your asking for trouble when you put 3s on one of the highest amp drawing 540 motors out there. It's worse than putting 3s on a cm7700, which has been done with costly results. The mamba max esc would shut down constantly. Don't confuse the feigao 540 motors with the mamba max motors. The mamba motors are much tamer, meaning they draw less amps per kv, similar to what a 380 motor would draw.
You will be better off running 3s with a cm5700 motor.

aqwut · 11.19.2006, 11:04 PM

it's hard to say what kind of amp draw the Mamba Max motors take... there's a reason why they made the mamba max esc 100 Amp continuous.... but depends what you want... I like anywhere from 35 to 45K rpms for the motor.... I'd rather use more cells less amps than less cell and more amps..... .. I guess heat's the biggest problem... the motor can only take up to 100 degrees celcius.. "I think"...
but the mamba max 5700 or 4600 would definately be a good choice.... I have to agree with Speedy...

Tom F · 06:15 AM

Well the draw is 'supposedly' 106A, and the motor is rated for 1000W (which would make sense on a 3S pack under load), although I agree the draw is likely to be substantially higher... especially under startup conditions.

It would be so much easier if they provided more/useful specs with these things!

So i shouldn't try it?

My understanding is that the MM will soft current limit, although i've always found the draw from this can to be insane...even on 6 cells.

Don't want to push it too hard...

I'm saving for an EagleTree...it's getting old having to guess at these things without actually knowing what's going on.

The XXXS G+ is extremely light with extremely low mechanical resistance, which will help reduce the draw, but i don't know how far.

Anyone know under what conditions the current draw ratings are measured? I'm assuming it's not stall, so what is it? Average? At max efficiency?

Edit: I'm not worried about heat. At least not in the motor - but I can see it being a significant problem in the ESC. As i said in my first post, I will be making a switch to the Mamba Max 4600 system ASAP, this is an intermediate thing, mainly out of curiousity ;)

I have a bunch of audio projects that i need to finish first though, so that will have to wait for now :(

SpEEdyBL · 11.21.2006, 07:26 PM

I would be more concered about you damaging your motor and batteries than the esc. Don't pay attention amp ratings and power ratings.

The only motor ratings that are important are: (in order)

resistance: the lower, the more amps it will draw (max. amps=v/r)
Io (no load current): the lower the more efficient the motor
kv: used as guide to determine the correct voltage for the application.
rpm limit: only advertised as a safety limit. Ideal rpm limits are when the motor overheats regardless of the load.

Scoob · 08:07 PM

I have a 540 8s that I run on 2s lipo and I think it would be at the upper limits on 3s lipo and I'm kind of scared to try it. It just seems like it would fry something or strip some gears. I would really be scared with a 6s. I agree with speedy. The 540 motors are on a different level compared to the Mamba motors. They pull a ton of current and output a ton of power. I would think the 6s on 2s lipo would be insane in a tourer much less 3s lipo. My 8s will push my RC10T4 truck to 39.5 mph on a Max Amps 2s 6000 and it could pull more gear but I'm happy with it.

I also have the MM4600 in a T4 truck. It is run mostly on 2s for a smooth tractable race setup. I have run it on 3s a few times and it's pretty powerful for sure but not that much more than the 8s on 2s lipo, I think it hit about 45mph. Were you planning to run the 4600 on 4s? Anyway, I'm rambling now.:010:

Tom F · 07:53 AM

The ESC is here :D

I just tried it on my Apogee 2S 3800 pack, 14T pinion, ESC straight from the box.

OMFG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!

It's absolutely insane!

I didn't go over half throttle, and it was barely flexxing its muscles and it is already too fast. I was running on WET GRASS and it was just holding the nose in the air the whole time.

I knew it was going to be good, but i was unprepared for this. Just shows how much that crappy hacker ESC was holding it all back.

Screw 3S...no need for it.

:043: :043: :043: :043: :043: :043: :043: :043:

After 5 minutes of idiotic grinning my feet were getting cold (no time for shoes...) i came back inside for fear of hitting something.

The ESC was ever so slightly warm, batts stone cold, and the motor slightly warm.

I'm going to back the timing off a bit.

Scoob...I want a speed demon project type thing (not that putting 4S lipo in a touring car is much of a project lol), so i was thinking tourer+lots of pinion+a pair of Apogee 3800s on the MM 4600 would be just the job. Undrivable, but fun. I have my doubts though now...this setup just flatout rips. I can't wait to try it in my tourer.

I was thinking on the same lines as you. Run on 2S on the 4600 most of the time for plenty of speed and power but good runtime, 3S for fun, and 4S just to try it.

Going to maybe pick up a 380c 13t for running with 3S full time - that would give me a whole load of runtime, without the unusable ammounts of speed :)

Thanks everyone for all your help as always.

Edit: Just got back. 25 minutes on the Apogee pack of extremely hard driving!

Tom F · 11.22.2006, 11:38 AM

Temptation got the better of me.

Phrases like 'unusable' and 'dangerous' came to my mind.

Nothing was more than slightly warm, but i was getting cold and my Tx was flat so i stopped after 5 minutes or so.

The heatsink and on the ESC was warmish, motor and batts were cool - but the fact that the motor wires might have been warm scares me...

It was astonishing though...on a wet road it was picking the front up at what must have been approaching 40 mph (this was in my T3)

Not sure if i'll do it again though...i'm not up for killing this Kokam pack because i don't fancy shelling out £130 for another one...

coolhandcountry · 11.22.2006, 11:44 AM

So last run was with the 3s lipo right?

Tom F · 11.22.2006, 12:01 PM

Right.

I think i will stay with 2S...at least until it dries up a bit ;)

Tom F · 11.23.2006, 02:37 PM

http://www.rc-monster.com/forum/showthread.php?t=4699

Video :)