EMAXX with MM 7700 what LIPOLY should I use?

[sLiKNiCk]

Hi everyone!

I am hearing many conflicting opinions on li poly batteries and I figure this is the best place to stop that.

I have an emaxx with the mamba 7700 with stock transmission but fully upgraded suspension. (I am willing to upgrade to single speed tranny if anyone has ideas on what is good there)

I want to run as long as possible and as fast as possible, doesnt everyone!

Anyone have some solid recommendations on what type of LI POLY battery and charger I should buy and that is compatabile with my truck?

my budget is around 200-300 for batteries and charger.

thanks

[skellyo]

First off, welcome to the forums.

Second...you really shouldn't even attempt to run a 7700kv motor in an E-Maxx. The 7700kv motor is meant for smaller, lighter vehicles like touring cars. I would do some research on what others are using in the brushless part of the forum before even thinking about buying Lipo batteries. Trying to run the 7700kv motor in your Maxx will likely cause huge amounts of cogging and possibly a smoked ESC.

[sLiKNiCk]

Well the 7700 was what was recommended for the truck as it is 1/10 scale and it's what I bought so I have no choice but to work within my boundaries.

So back to the question about using a MM 7700 with LIPOLY on an EMAXX so if you have any advice in that specific category it would be appreciated.

[wallot]

yes its for 1/10 trucks but stadium trucks that weight few pounds not 10+lbs maxx. 7700kv motor is for about 6cells or 2S LIpo. you will fry the motor if you try to move maxx.

even if the motor would be able to handle maxx weight 7.4V (2S lipo) x 7700kv is almost 57000rpm and you wont be able to gear it properly.

you can keep the MM controller but sell the motor and get something like 7XL or 8XL

[Serum]

Welcome nick;

The 7700 is meant for 1/10th scale trucks/onroad vehicles, not monster trucks. Since the e-maxx is a monster-truck it's not an option. the KV value of the motor is too high, and the torque isn't enough.

I suggest to read the sticky in the brushless section i wrote, it would explain quite a bit.

Bytheway; if you have got a question, you don't need to post it three times.

One time will do. Thanks.

[sLiKNiCk]

Well I did have it hooked up for quite awhile with 7 and 8 cell batteries and it ran great no blowing up like you say will happen.

Obviously I came to the wrong place... I'll leave now. My apologies if I wasted your tiem I thought this would be a nice place to gain some insight but I was wrong.

Originally Posted by sLiKNiCk

Well I did have it hooked up for quite awhile with 7 and 8 cell batteries and it ran great no blowing up like you say will happen.

Obviously I came to the wrong place... I'll leave now. My apologies if I wasted your tiem I thought this would be a nice place to gain some insight but I was wrong.

No one here is trying to scare you away, we just speak from experience. S can motors (like the mamba max 7700) just do not run well in a truck the size of an e-maxx. What is your gearing too? like 76 spur/ 9 pinion? The thing is that to really run that motor for any length of time you would have to gear down alot to compensate for the small size and high kv.

Please stay and have a good time, we are just trying to help.

Bye:018:

[sLiKNiCk]

Well I came here to learn and gain some experience but when I post my specs I just get slammed maybe I'm to sensitive but I just plopped down 200 bucks for a HIGHLY recommend motor and now I am being told its the wrong one.

I am pretty sure I have a 72 spur and 15 pinon

thanks cemetery!

I also have an email into Mike to help me along with maybe transitioning to a XL motor with my esc and LIPO... I just want to have as much fun and have as little chance as possible in destroying my truck.

[skellyo]

Originally Posted by sLiKNiCk

I also have an email into Mike to help me along with maybe transitioning to a XL motor with my esc and LIPO... I just want to have as much fun and have as little chance as possible in destroying my truck.

Awesome! Mike will certainly be able to help you out with parts to get your E-Maxx eating nitros for breakfast. A couple of other things you'll need to invest in when going to the XL are a UBEC for the MM, rc-monster heatsink/clamp if you get the regular 540 XL (instead of a 540C XL), steel idlers and 5mm bore pinion(s).

[Serum]

Please read the sticky in the brushless section i wrote Nick, i am sure it will give you an insight on the setup you are currently using, and the reason why we advice you strongly not to use it.

Please don't be too stressed out, i just read the posts in reaction to your opening post, and i don't see anything offensive in it. Apparently you are disappointed in the purchase you made; Who did you bought it from and who advised you to use it on the maxx? Or was this based on the assumption of the 1/10Th story? (either way, it's quite obvious there is/was a misunderstanding going on)

Now back on topic to the more relevant stuff;

It would be better to get a 7XL or 8XL and run them on 4S lipo. Maxamps 8000 4S2P packs would be a good investment, for a charger you can use the Multiplex that Mike sells. You also need to buy a Ubec, since the internal BEC of the MM is rated for 3S maxx. And with a strong servo turning the wheels of an MT, it's better to use a UBEC anyway.

If you set the timing on minimal, punchcontroll to the max on your MM controller, the drivetrain can hold it.

[AP Alex]

Your at the right place, and Mike is the right guy for the job. These guys are unbelievably intelligent in their field. It's fun to see them argue; especially when they write these long formulas to explain themselves. I share information with my students all the time about these guys, their inventions, and ideas. All to help promote higher eductation. I run the MM 7700 in my TC4 on seven cells.

[Finnster]

You definately came to the right place, I doubt there is another collection of people you will find that have as much experience with large scale brushless conversions and setups as you will find on this forum. Now please trust us when we say that the 7700 motor is not the motor you want to use in an Emaxx. The esc is solid, but it needs to matched up to the proper motor.

From the Castle creations website: NOTE: The Mamba Max Power System is NOT for use in 1/10th scale monster trucks. Who ever told you you could use a 7700 in an Emaxx is horribly horribly misinformed, sorry to say. If it was the LHS, maybe they can take the motor back. Maybe not used tho. If you think about it, its a "1/10 scale" system, but a 1/10 Emaxx is heavier than a 1/8 scale buggy. ;) A decent BL system for a Maxx sized vehicle needs to be ~1500W (~2hp.) To do this on 2S Lipo would mean an amp draw of around 200A+, twice what the esc is rated at, and far more than a 7700 sized motor could handle.

Really, the best way to go w/o dropping a huge amount of cash on a high end motor like a Lehner or Nue, is to get a Feigao 7XL or 8XL and run it on 4S Lipo. You will have a very fast and reliable truck, over 40 mph. I have a 8XL, and would personally recommend it. Mike has then for $90 IIRC.

Lastly, to do this you need to disable the on board BEC and run a Rx pack or buy a external BEC. External BECs have caused alot of glitching for me, so unless you have a digital radio like a Spekrum, I would try a Rx pack first to get things working, then play with a BEC from afterwards. Also, with a good BL system, you will never need 1st gear either lock the tranny in 2nd (easy) or get a single speed conv. from Mike (easy too, just extra $.)

[Mr.lst]

I was going to say the same thing as cemetary gates, just relax no one wants to offend you they just want to see you with the right product for your application so that you are not throwing your money away. btw welcome to the forums

[BP-Revo]

SlickNick, it is not that you are being slammed or anything. I don't beleive anyone called you an "idiot" or "moron."

All we are saying is that the Mamba Max system is designed for smaller, 1/10 scale vehicles in the range of 2-4 pounds, 5 at most if you use a lower KV motor. The 7700 is usually completely reserved for touring cars.

An E-Maxx, while still 1/10, is a Monster Truck, and on the Castle Creations website, there is a statement that the Mamba Max system is not for use in 1/10 scale Monster Trucks.

While it can work somewhat, the system will be greatly stressed and it will cause premature wear and failure.

I guess a comparison is using a honda civic engine in a Dodge Ram or something. The engine will eventually get the truck moving and such, but its going to be working pretty darn hard and won't give ideal performance and "milage" (aka runtime).

While it would be HIGHLY recommended to buy a motor that is large enough to deal with the weight of the E-Maxx, I guess it is possible to run the system. My suggestion is to use the lowest gearing possible and gear up from there. Use no more than 2S lipo.

Also, just so you know, an XL motor can cost as little as 70 bucks or so, and the MM motor can be sold for nearly that much, so you won't be exactly wasting money.

[Mike.L]

unless you ran dual 7700kv mm motors on the emaxx, on 2 or 3s lipo, then it would be better but that plain dumb, sorry heheh.

please do say where here to help for the better not for the worse.:)