MMM vs MM with A123's.. Check this out boys :D

Hi all,

Got my MMM last week and finally managed to get it out for a run on the weekend. So far so good, its had about 6 packs through it, the fan is still spinning, and everything is working, HURRAY! I had to solder 3 "jumper" motor leads to connect to the ESC as the 8XL wires are real short, and the Tekno Revo conversion mounts the ESC quite far forward.

My setup:

Revo 3.3
Tekno RC Revo Conversion
5s1p A123 2300mAh home made packs ;)
Feigao 8XL 2084kv motor
Mamba Max with CCBEC@6v and Monster Mamba Max ESCs

Alright, so I got out to the track and decided to give the Mamba Max one last run before I put the monster in. The first graph below is with the Mamba Max, and the second is with the Monster. Gear setup and batteries were the same for both runs, and I topped up the batteries before each run as well.
I was using the 36T spur gear, 15t clutch (clutch shoes on backwards and spring removed), with 5s1p A123 batts. Oh, I'm using the DPRII-150 to create the graphs.

MM


MMM


The graph sections are approximately 2 minutes long, but they're taking from slightly different times in the run, due to me flipping the car and having to run out to turn it over lol.

How insane is that? Max amp draw with the MM was like around 62A. Max amp draw on the MMM was around 86A. Thats with exactly the same setup and batteries.

I'm definitely impressed with my Monster, but now I'm facing a new problem lol. We do 6 min races at my track, and with the 5s1p setup and the MM with 36T spur, I was barely getting 5.5min and around 6.5 laps. Still short of the mark but not bad. Now with the larger amp draw from the Monster, I'm getting barely 3 min run times, and I can hardly race with that lol.

My 5s1p packs are 392g and 396g each. I've tried them in 5s2p, but the car is just WAY to heavy and it'll break something if I do a dodgey landing, which is definitely bound to happen lol.

Would people recommend dropping to 4s2p with the same 8XL. As you can see from the graphs, the voltage sag is huge, so I'm definitely not getting max RPM out of the 8XL at full speed with the 1p setup anyway, so I figure 4s2p would be much less voltage sag and so the top speed should be somewhat comparable to the 5s1p setup anyway.
If its not fast enough, I can always pickup a 7XL, but I'm trying to avoid spending more dosh, if possible.

Post up your opinions please :D

Thanks guys

[What's_nitro?]

That's pretty amazing that the FET resistance is low enough compared to the MM to allow that much more power. Technically if you got a different motor that would only draw 62 amp peaks you would have longer runtime since the controller is eating less of the power.

[MTBikerTim]

One more question. Hows your performance? You were saying it was a bit sluggish before, how is it now? Great work too. Shows how the MMM can be harder on batteries then the MM.

Apart from runtime, performance seems to be a bit better with the MMM. It accelerates much harder from a standing start, and when hitting jumps, it seems far more aggressive. I've got the punch control set to 40% for both ESCs.

With the MM when it was hitting 2nd gear and getting to top speed, it seemed to be not as fast as when the Revo was nitro. That was with 5s1p. When I tried it with 5s2p it was MUCH better, as the amp draw was split between both packs and therefore was less voltage sag. Even the MMM is not quite as fast as the nitro down the straights, but the voltage sag is even more pronounced with the MMM so I'd imagine when I try 2p it'll be much better.

I haven't tried 2p with the MMM yet because when I had the 5s2p in the car, I landed a jump badly and broke a rear shock shaft :(.
Thats the main reason for seeing if people recommend 4s2p and a higher kv motor like the 7XL :D

[MetalMan]

5s1p A123 is quite weak - 1000amps peak. Running 5s2p in my "slipperential" Revo (the one which lincpimp now owns) I would get 10-15mins with a 7XL and MM geared for ~45mph top. Since it was a custom conversion with the motor only slightly offset to the left side, I could easily run 2s2p next to the motor and 3s2p on the right side to achieve decent weight balance and CG.

[JERRY2KONE]

Knowing that the Fiego motors are not very efficient and tend to crate a great deal of heat maybe a motor upgrade would give you slightly better run times, not to mention better performance overall. just a thought....

[Sammus]

You could also get a 11XL and run 7s1p... dunno how much it would help though :) cheaper than a proper motor upgrade :P

[JERRY2KONE]

Originally Posted by Sammus

You could also get a 11XL and run 7s1p... dunno how much it would help though :) cheaper than a proper motor upgrade :P

Maybe cheaper up front $$$, but with a better motor in the long run you would end up with a better running motor that does not get hot like those XL motors. In this hobby we always tend to go with the cheaper option trying to keep our budget down and end up spending more overcoming other issues, but trade off on the overall performance, which costs us in satisfaction.

[Sammus]

Originally Posted by JERRY2KONE

Maybe cheaper up front $$$, but with a better motor in the long run you would end up with a better running motor that does not get hot like those XL motors. In this hobby we always tend to go with the cheaper option trying to keep our budget down and end up spending more overcoming other issues, but trade off on the overall performance, which costs us in satisfaction.

Yeah too true...though I have an 11XL in my revo, and 7 A123 cells on the way... :) Hope it goes alright, I'll only gear it to 30-35mph though, don't need a MT to be a speed machine, got plenty of others for that :P

Haha I'm sure I'll be investing in a better soon (as soon as the missus allows ;) ), but I wanted to see if the whole brushless thing was feasible using my existing A123 batts.

The 8XL does seem to heat up real quick, but for $70, I don't really mind abusing it until it dies.

It's always worth buying good stuff up front, hence the MM and MMM's I've got, but I was really unsure what kv motor to get with my batts etc. Now that I have an idea of performance vs power delivery and battery capacity I can make a far better decision. Would have been worse if I shelled out $300 smackers for a Neu and then found out I got the wrong kv for my setup :D

On that note, how does one work with the Neu naming convention, and which one would you gents recommend for me when I'm running the 4s2p batts? I'll be racing with the Revo, so I'll need at least 7 mins run time (10 would be better) and enough speed to keep up with the nitros, but I'll be happy if I can flog them down the straight! :D

[JERRY2KONE]

Well it seems that the two most poular motors of choice on RCM are the 1515/1y or the 1521/1y depending on how fast you want to go. There have also been a slim few that have gone all out and gotten the 1527/1y, but resolve to the fact that it is just toooooo much power for Revo scale trucks for good handling purposes. If you want to race with the nitros and use the MMM you may want to go with the 1521 and gear accordingly. Batteires can always be reconfigured to sute your satisfaction. Good luck with that.

[Sammus]

I read somewhere that the Neu's start to lose efficency above 50,000rpm. The way I think of that is to get close without going over. You 4s A123 setup should be 13.2V so you want to aim for something close to 50,000/13.2 = 3787kv.

I'm pretty sure the tekno fits 1515 size, so you would be looking at either the 1515/1D or 1.5D (4100kv and 2700kv respectively). I think the lower kv would be the better option so you have the option to go up to higher cells if you ever feel the need, whereas with the 4100 youre already pushing it beyond optimum with 13.2V (but how often will it be peak revving?)

To get closer to the 50k range you could go the 1512/1.5D (3300kv).

All that said, its just theory I've put together from my research without actually having any experience with these motors or cells, I'm fairly confident in my words, and I'm lead to believe any of the Neu's would be a huge leap up from a Feigao, but follow at your own risk :)

J2K: I dont think anything longer than 1515 fits in the revo with the tekno mount.

[sleebus.jones]

Originally Posted by cdis

Would people recommend dropping to 4s2p with the same 8XL.

I'm a proponent of higher voltage, so I'd say you're going the wrong way. :) I run 6S1P in mine (10XL) and it seems to run pretty well, but I haven't been smart enough to keep my finger out of the trigger and not break something...so i'm kinda lacking at giving you a runtime, haha.

I gotta second jerry's comment of "In this hobby we always tend to go with the cheaper option trying to keep our budget down and end up spending more overcoming other issues, but trade off on the overall performance, which costs us in satisfaction." That's a very true statement.

[SpEEdyBL]

hey cdis, are you sure the timing set on the mmm is the same as it is set on the mm? Higher motor timing will increase amp draw.

[skellyo]

I think that if you were to make several runs with each ESC so that we could have some sort of larger sample size than a single run, it would be much more compelling evidence. I'm just not a believer after a single run.

It could be something as simple as a particular patch of track that had more traction that you didn't hit on one, but did with the other. Without a very controlled test such as a specific torque load on the wheels, it's really nowhere near accurate as too many other variables can pop up.

You guys take it for what it's worth, but I'm a firm believer that this data doesn't prove anything unless it's repeatable.