Is 4S+3S in serie possible?
 

Hi guys, i was wondering if it would be possible to plug a 4S and a 3S battery in serie?

To make the power the closest possible to 26 volt (for Neu 1527 1d 2300kv)
That would make 25.9 volts?

It would run 2X= 4S+3S in serie

And also would the MMM esc be able to handle 25.9 despite the 25.4 volt spec?

Thx for any suggestion to get that motor running at 26 volt? :)

1527
 

I also have that motor on my conversion. Be prepare to put out the flames after a couple of minutes. The motor is an amp hungry and I was running on 6S, I think the MMM won't handle the continous current. I beleive it runs 200 amp or more under load depending on gearing. Don't do it and by the way I was running a Hydra 240 with watercooling in it and everything was running cool at less than 100 degrees then the flames started coming out. Goodluck.

Yes you can do 4s + 3s for a total of 7s, as long as the battery cells are the same. The MMM will not handle 7s (6s max). However, 6s would be more than enough for that motor.

Yes, you can run any series arrangement you want. You could use 4s+3s, 3s+2s+2s, 1s+1s+1s+1s+1s+1s+1s, etc. It doesn't matter.

However, the MMM is designed for 6s max. 6s is 22.2v nominal, but 25.2 fresh off the charger. 7s is 25.9v nominal, but 29.4v fresh off the charger, which is too high for the MMM. That ESC has a device to absorb brief voltage spikes above around 28v (IIRC), but will blow on 7s.

That's a 4-5s motor. Fully charged a 7s pack is 29.4v.

Thx guys, that made it more clear now.

Transtalon, when you say flames, there was really flames coming from the motor?
Do you know what would have cause the flames?

Thx ! :)

but the batteries still need to be the same make/model/capacity and have the same number of cycles.

without this the batteries will be un-matched and one may go below lvc before the other

Ok that mean same Mah, both like 30c, and thats it?

No same amount of cycles/discharges between the 2 packs. If one pack has been used 40 times, and the other only 10 thee your packs will probably be below voltage at different times. That means you could damge one of your battery packs and that can get expensive!

Neu
 

No it's not coming out of the motor but your ESC will burst into flames. I was running a 5S setup with that motor with 30 pinion and 63 spur on a heavy extended Lst2 17 lbs everything was okay but with a 6S after 5 min of driving it and the temps were below 100 deg motor and esc. It just started smoking and it started to go on flames 3 times with the same setup so pls don't try to do it if you're not prepare as you will loose the entire truck if your not fast. I kill the fire in about 10 sec and first pull out the batts before anything else. Just giving you a warning, as this is no joke. I will run it on a good 5S batts. The motor is very powerful but very amp hungry with higher rpms. Goodluck.

Ok, thx for the info guys much appreciated,

I am also wondering something, lets say you run a Neu 1515 1.5d 2700kv on 6S with the MMM, polyquest 4500mah 30c batteries
all you change is the motor to a Neu 1521 1.5d 1900 kv , is it more powerful than the 2700kv 1515 1.5d? (not taking into account the rpm capabilities) just power wise?

Or its just run cooler?

sorry i am very curious when i want to learn...

Thanks!

Mike

For starters a 2700 kv motor on 6s is a very power hungry setup and generally not recommended at all (except maybe for speed runs). But if you change only the motor and not the gearing, it's gonna have less power with a lower kv. Bigger motors are capable of handling more power and will typically run cooler than a smaller motor at the same power level.

If you changed the gearing of the 1900kv to match the top speed of the 2700kv setup, the 1900 will run cooler (even if the motors are the same size).

What are you going to do with the car? Why do need such high rpm? If it's just a speed run car then fair enough, but if it's just for general bashing, I'd try a different type of setup.

Like i said, im not talking about rpm, its just power output, and it is for speed run :)

What vehicle, and what was your target speed?

It will be for a revo, but my speed target is not important, i just want to know if the Neu 1521 1900kv will produce more power on the same volt as the neu 1515 1.5d ?

Its not speed related, i can give you all the detail but it will still not answer my question, i dont want to sound like i dont care tough lol its for a revo for now.

We are still working on stability and tires setup, but so far we got 81.9mph on a run i lost control... it showed 84 mph on the radar and 81.9mph on GPS, then i lost control in side of the road and it did cartwheels lol Lonnnnnnng cartwheel!! :D

We already found a better setup, i just want to let my friend order the right stuff, it will be used for other vehicle, its more for informative purpose right now, im trying to see what would be the advantage of running a Neu 1521 on the same setup he have right now.

He also want a 12S esc...

:)

Target speed is incredibly important, since it takes a specific amount of power to move any given truck to that speed- if you dont have a goal/ target speed, how can you know which motor/kv/voltage/lipo combo would be required in order to produce the required power? Your only hope would be to hazard a guess and use a setup that was clearly overkill, but then you may find it costs too much or goes up in smoke (or the trucks driveline does)...

Anyway, look at the Neu website: http://www.neumotors.com/Site/1500_series_.html

You will see that the 1515 1.5d is rated at 22v (6s lipo) and 1250 watts continuous, 2500 watts peak.

The 1521 1.5d is rated for 31v, 1750 watts cont. and 3500 watts peak.

Assumming they used the maximum voltage to generate those wattage ratings, then with a little bit of my amazing mathes skills I get the larger motor producing about 1100watts on 6s and about 2300watts peak.

Then again my mathes is shite when it comes to the more tricky theoretical stuff like this, so dont take that as gospel.

What I will say though is that the 2700kv neu being ran on 6s is enough to kill the MMM if you arent careful- a noob ran his 2200kv castle motor on 6s and geared for 75mph in his Savage flux, and toasted the esc. Granted your revo will be lighter and only used for straightline stuff, but the motor is a real amp hog; I would personally chose the larger lower kv motor option and run that on 6s, until he/you get a HV esc, then current draw wont be half as bad with a nice low kv motor.

Will be needing vids of your speed runs though, its the law... :yes:

Heres the video, :rules: :lol:
http://www.youtube.com/watch?v=-i0ludmC4fA

We installed a heat sink on the neu and now it dont overheat for the few sped runs we do, we let it cool down after a couple of runs.

As far as speed , we want the fastest possible without over heating, if it have low kv i will regear. 90-100mph is what we are looking for in some truck we plan to use.

But my primary question was to know if the 1521 would perform as well or more with the MMM on the same setup, we will regear if it dont spin fast enought, i know how to use the speed calculator and the kv rating.

Thx for the help :)

Jesus, thats fast enough to make you a dude in my books! :yes:

Anyways, there is a guy by the handle of jzemaxx who put a neu 1521 1.5d in his 1:8 scale XTM MMT, though he used a custom ordered 1524 1700kv motor for his record attempt and made it to 80.4mph, though he was running a somewhat higher voltage @ 10s (several threads, this and this one are a good read).. I think the smaller neu you are using will produce more power on the same voltage compared to the larger neu (based on my fuzzy logic/mathes), but if you were to step up to a higher voltage MGM, use the larger and lower kv neu, it would easily produce much more power to get you to that ~100mph goal. My only concerns then would be tyres exploding, tranny and diffs exploding, and general aero dynamics- very long upside down skids as seen in that video.

However, you can belt the tyres or use MT foams, beef up the diffs with rc-monster hybrids or LST2 modified diffs to fit the erevo bulks, and a drag-bar or very big wheelie bar should help keep the nose down, along with maybe a front wing.

Yup that was me......80.4mph on camera. Did end up going 85mph on the GPS off camera several weeks later, but got tired of replacing tires so I quit. The XTM dwarfs a E-revo which is much lighter so speeds should be easier to attain with it. I would think with my old setup on a E-revo it would have gone close to 90mph. I was running 12S. :yes:. I had another setup that was ready for testing that would have pushed the XTM over 90 with a 1527 and 20S. 20lbs with 12S, means with 20S that truck would have been close to 25lbs:surprised: Tires would never have held....... Now I'm racing and the XTM is parked and hasn't been off of shelf for quite sometime.