Help with E Maxx with MM esc and 5700kv motor
 

Hi guys, this is my first crack at a Brushless conversion I'm running a stock E maxx with a single motor 5700kv CC motor and MM esc using a external UBEC and a 2100mah Thunder Power Lipo. When I the bench this everything seems fine with lots of power. I did my first test run today on grass the motor has alot of power it was doing wheelies off the start I ran the truck for about 10 mins and noticed the battery become weak ( I was lucky to when the battery cooled down the swelling went down and I didn't destroy the battery). When I checked the Lipo pack was too hot to touch and swelling the ESC temp was about 120 F and the motor was about 100 F.
My question are:
Is my setup too small, battery, motor or esc?
My gearing was 18 pinion and 66 spur gear is this not matched right?
What if I put to Lipo's in parallel would this help the battery to run cooler?
Thanks for any help on this matter.

The mamba motors are too small for the E-maxx. What voltage are you running?

I would also say the batt capacity is too small as well, paralleling them would help.

I'm running 3S pack 2100 mah 11.1V.

The whole system is a bit small, But i have heard of people runing similar with sucess, though they were geared about 12 or 13 tooth pinions. I think you need at least a 4000 in 1/10 or MT applications, but thats me. I know 2200's don't live long, in high amp loads. I think a 9XL and 4s w/Ubec would be a better setup

You would be better off running 4s (about 5000mah range or better) and a XL size motor (maybe 9XL). You can still use the MM controller if you use a separate BEC and disable MM BEC.

crazyjr, are you referring to a larger battery about 4000mah? Maybe I can double up my other Lipo in parellel I have 2 of these 3S 2100mah. I just thought I would give it another try before trying a new setup since I already have the stuff. What do you think?

Yeah, a larger capacity battery will have more current capacity. If amperage draw is determined by multiplying the C rating by the capacity, it only stands to reason that a higher capacity cell will hold up better. Paralleling your 3s packs would definitely help since each will supply half the current. BUT, make SURE each pack is at the same voltage when you hook them together, and charge them like that from now on. And, each pack should be the same age and have seen close to the same number of cycles.

You don't really need a whole new setup, just an XL motor. If you want to stick to running 3s, you could get a 6xl or 7xl, but you will NEED to parallel those packs. And you should still use a UBEC. Even then, I wouldn't gear too high or those motors will pull too much current for the MM.

BrianG, I know you really know your stuff thanks for the help! Should I parallel them and leave them that way even when charging them? or should they still be individual charged? What about balancing them if they are to be charged together can this be done? or would I balance them separately before charging? I know I'll buy a new motor soon but was hoping to use this for now until the new one comes in. Do you think the gearing I'm using will work 18-66 or should I use something else?
Thanks

Yes, they should be charged as a parallel unit to avoid any differences in voltage when you hook them together. Balancing a parallel pack will be a little tricky using one balancer, but you could use a pair of balancers, but hook the main cables together to hook to the charger.

I can't really comment on Maxx gearing, but I would shoot for a max of 20-25mph tops, whatever spur/pinion that takes. Try using the "parameter solver" in my sig; enter the everything except the pinion and it will calculate the pinion needed to meet those specs.

People that run the MM motors in a Maxx have only done so in 2WD AFAIK. 4WD simply places too much load on the motor since there is less slippage.

I'm running the same setup.


I'm running 10/72 gearing and that's still too high in high range. This is still a very hot setup. I'm running a 3S 4000 Lipo and it works well but still gets pretty hot.

You are way overgeared with your current setup.

I would suggest dropping way down on your gearing and possibly getting a bigger Lipo pack.

Correct, You are pulling a lot of amps getting it moving. I figure close to 40 amp const. and well over 100 amp spikes ( I seen a 120 amp spike with a 9XL on 5S). With your setup, the weak links are battery and gearing. With the stacked 3s, it might work, But i'd go with a 5000 mah Maxamp in two 2s in series, for 4s setup W/external BEC and i'd drop the gearing to at least a 12 pinion and work from there. If you stick with the 5700 Motor

Can a MM ESC handle the 4S packs with the overvoltage cause the ESC to over heat and shutdown?

I honestly don't know, the older models will do up to 5s ( Mine did at least), but the newer ones seem to be pot luck. Some will and some have problems, I think if you tryed it with the 5700 motor, if it worked, it would in fact heat up a good bit