MAMBA25 Heat Problem

[trevor0876]

I installed a Mamba 25 ECS & the 6800KVA Mamba brushless motor in my Mini - T a couple of days ago. I was running a 3 cell LI-PO pack with it and a 9 tooth pinion gear. I set the ECS up for the proportional brake w/ lock-out, reverse throttle & brake strenght @ 50%, the cut-off voltage @ 9V, the timing advance at normal (#2 setting), and the starting power at normal (#2 setting). The system worked well for about 10 - 15 battery cycles but the motor seemed to run hot. I check out the clutch set-up and differential / drive train to check for any sticking parts but everthing apeared fine. Finnaly on the last run I lost pretty much all the power with a fresh battery and the motor was smoking hot. Unfortunately for me the motor was cooked and had to be replaced. (replaced it with the 8000KVA version of the same motor).

I am new to the brushless systems and I was wondering if I am doing something wrong with the set up or if I just got off to a bad start?

[glassdoctor]

I'm not a 1/18 guy here so maybe I'm off base here... but dude, you are running 11.1v packs and 6800kv motor... and just switched to a 8000kv motor? That's 90,000rpm!!

I don't know that any motor will live forever in this setup. Are other guys running setups like this?

[kufman]

I know other mini drivers will say that a 3s on the 6800 is ok, but I think that 75,000 rpm is way too high!! Keeping the rpm's to 50,000 has always worked better for me.

[pinolelst]

yep...80,000 rpms is too much to ask for repeatedly.I sometimes run a 8000kv mamba in my rc18t on 3s lipos but keep the runs short.It was clocked at a solid 50 mph with the stock 13 (?) tooth pinion but largely uncontrollable except in a straight line drag race :D

So..use a lesser kv motor and reasonable gears for less heat and more usable power and keep the 8000kv motor for drag racing/short duration running.

pinolelst

[starluckrc]

5400 is a good 3S setup. I wouldn't go any higher than that in kv if running 3S consistently. It's also too much power for the Mini-T to handle anyway. Mine kept it's nose in the air with the 5400 motor.

[trevor0876]

Thanks guys. I talked to a couple of guys at the local RC store that are running the Dynamite C4 9200KVa motor w/ the Quark speed control and like myself a 3 cell LI-PO pack in the Mini T. One guy has had the system for a couple of months and had no problems (other than keeping the car under control!!!). The new 8000KVa motor I installed runs quite a bit cooler than the old 6800.

Does anyone know what the max temp these motors should reach?

[glassdoctor]

Are you geared about like those guys are? Your motor may have had something wrong... bad winding, bearing, etc.

Generally you want to keep them under 200* max.... to keep from doing damage. Most will say aobut 220-240 is when magnets will lose some zap.

I'm happy if my motors stay under 180.... but I've had them up to 200+ with no apparent problems.

[trevor0876]

I'm not sure about the other guys, I went from a 11 tooth pinion down to a 9 with the bigger motor. I just ran my truck and took a temp 198!!!

[glassdoctor]

198... is that cooler than the 6800 was running???

If you ran it really hard that may be ok... or do you ever push it harder?

It's definitely right at the edge imo. But I run motors about 10x bigger so what do I know? :)

[trevor0876]

I never did a final temp on the old motor but I am sure it was much hotter than that since the motor and the wires were smoking. I've been running the car in my basement where there is little space to get up to top speed, its more start & go type driving with lots of donuts!

[ElectricThunder]

198 is REALLY hot. I don't think 3s lipo is advised or covered by warranty by Castle on the 8000kv motor (and apparently with good reason). Try a 2s lipo or 6 cell NiMH pack. 3s is just a lot of voltage through that poor little high kv motor. Or do what starluckrc said and run the 5400 on 3s.

Whew...that's a lot of RPMs. :eek:

[trevor0876]

I checked out the mannual that came with the set-up, 3 cell LI-PO is Ok as long as you use the 9V power shut-off option. I see here that 4 cell is not reccomended. (I dont recall seeing a 4 cell that would fit the Mini anyways).
Cheers!

[ElectricThunder]

I checked out the mannual that came with the set-up, 3 cell LI-PO is Ok as long as you use the 9V power shut-off option. I see here that 4 cell is not reccomended. (I dont recall seeing a 4 cell that would fit the Mini anyways).
Cheers!
For the ESC 3s is fine. I'm talking about limitations/specs for the motor.:)

[trevor0876]

Just checked out castles website & downloaded the a PDF that explains how fast the Mini T will go with different motor and cell combinations using stock pinion gears. The competition "X" package (C/w 8000KVa motor & Mamba 25 ESC) mentions using 3 cell LI-Po's makes the car undrivable unless you have a long track AKA: Drag Racing. I did not see anyting about not using the 3 cell for warranty purposes but it does suggest using 6 cell NI-Cads. It also mentions the drivetrain (differentals) life span will be greatly reduced.

I'm new to these forms and I'm not sure if attatching web info is allowed so but here is the link. Check it out!!!

http://www.castlecreations.com/support/documents/Mamba%20Setups.pdf

[glassdoctor]

Castle has run 3s on the 6800 and 8000 motors for speed tests... and I don't see anything on their website that says you can't do this.

But if you do this you have to understand it's pushing the limits.

You can't just throw this combo together and run it and not have some issues. The gearing must be right and you can't expect it to whatever you want, such as run through grass all day, etc without issue.

This goes for all r/c stuff... when you go extreme you still have to stay within the laws of physics and common sense.

Castle says they have hit 60mph on 3s/8000. That's crazy stupid speed!!!

Are you doing some serious speed runs with yours? If not, you are better off with the 4200 or 5400 imo.

Edit: I see you just posted and checked CC site too... for the same info.

[trevor0876]

This all started with a couple of buddies buying the stock cars and racing them. We all had a great time just running right out of the box. One day someone showed up with a new battery pack (6 cell rechargable Ni-Ca) while the rest of us run the throw away energizers. Then the big block motors came, everyone bought the new motors batteries etc. It just got crazy from there. It's more of a show now, everyone is trying something to beat the other guy for a day. I'm the first in the group to go brushless so I am learning from my mistakes.

I will admit that my car is very impractical for everyday driving and racing, but it has been fun (and expensive) experimenting with different hop ups. I haven't had a chance to run the car in a place where I could really wind it out (too much snow outside), the longest run I have done is about 120 feet of slick concrete inside the shop, but I have no doubt when Castle says the car will do 60MPH I believe them.

I've always raced Nitro trucks until recently and I'm pretty sure the Mini T will blow the doors off my Revo if I can steer it that is. I guess summer will tell all!!!

I would not reccomend the set-up i have for anyone who doesn't have deep pockets for repairs thats for sure, but I was looking for someone who has tried what I have and what tricks they might have up their sleeve.

Thanks for the input!!!

[ElectricThunder]

Just checked out castles website & downloaded the a PDF that explains how fast the Mini T will go with different motor and cell combinations using stock pinion gears. The competition "X" package (C/w 8000KVa motor & Mamba 25 ESC) mentions using 3 cell LI-Po's makes the car undrivable unless you have a long track AKA: Drag Racing. I did not see anyting about not using the 3 cell for warranty purposes but it does suggest using 6 cell NI-Cads. It also mentions the drivetrain (differentals) life span will be greatly reduced.

I'm new to these forms and I'm not sure if attatching web info is allowed so but here is the link. Check it out!!!

http://www.castlecreations.com/support/documents/Mamba%20Setups.pdf
I read that as well. They didn't say anything along the lines of "you can do this too"...:D

It doesn't really matter though. 11.1 volts on an 8000kv motor is asking for trouble sooner than later. It's easier to get away with higher voltages on a smaller motor though. I bet once you can get outside and run the truck at WOT, things may cool off a bit just from some air moving over everything (hopefully?).

Stock up on parts too...:D Minis into solid objects at 60mph tend to break stuff. :eek: :D

[Duster_360]

I have 4 BL setups in 18th - all mamba 25 escs, 3 are non mamba motors and 1 uses a 5400 Mamba. I run 2S lipos and occassionally just for S&G, I'll run a 3S. That will make it run hot like yours if I run it for long. The way someone explained this on one18th.com, the esc regulates the voltage for servo and anything above 6v is turned into heat. Thats a relatively big voltage drop from 11.1+ to 6v so there's a lot of heat generated.

None of my BL motors on 2S run more than 140F, and thats when its 90F outside. Escs are never more than barely warm. If you can't hold your finger on the motor for 3 sec it's prob too hot.

In the 18th I run a 3S in every once in a while, I've added a heat sink on the esc to help cooling. I watch how hot it gets and quit before it gets hot.

[glassdoctor]

I thought this before but didn't say it... often the extreme speed setups like CC did with 3s and 8000kv will work but it's "understood" that this is for short runs, not dumping your entire pack or bashing in the yard.

Just like "insane speed run" are designed to run for only a minute or so, so they can run a hotter setup than a car for general use.

[ducati777]

You guys seemed to have missed where he described where he runs... in his basement.... which means its all stop and go, which generates more and more heat on the higher kv motors.

He's already said its more about one upping the other guys. In this case I'm sure he'd buy a 12000 kv motor if it were made, just so he could claim a higher kv. Despite it actually creating more headaches for him.

The trick to these things is high volts, and low kv, and proper gearing. I'm running 3s lipos as well, but only 3950 kv on a big can feiago motor. Zero heat, 45+ minute run times, and a theoretical top speed of 48 mph. Its a handful!

So the question you gotta ask yourself, is it more important to sound fast, or be fast? Because in your basement a 5400 is going to whoop on the 8000.

[ElectricThunder]

You guys seemed to have missed where he described where he runs... in his basement.... which means its all stop and go, which generates more and more heat on the higher kv motors
I bet once you can get outside and run the truck at WOT, things may cool off a bit just from some air moving over everything (hopefully?).

Stock up on parts too...:D Minis into solid objects at 60mph tend to break stuff. :eek: :D
I didn't! :D