Is 4S+3S in serie possible?

[Over_revO]

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? :)

[transtalon]

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.

[bdebde]

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.

[BrianG]

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.

[Metallover]

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

[Over_revO]

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 ! :)

[Arct1k]

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

[Over_revO]

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

[T-Bro]

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!

[transtalon]

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.

[Over_revO]

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

[MetalMan]

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).

[Patrick]

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.

[Over_revO]

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

[suicideneil]

What vehicle, and what was your target speed?