3S setup using the newer high C Lipos

[Cain]

Before I start, I want to say YES, I KNOW that ideally higher voltage plus a lower KV motor is the ideal setup. So before anyone goes on a rant about that, you don't have to.

Now, to my question:

looking at the current crop of lipos, the C ratings are really getting up there. Based on that, I have been toying with the following setup, depending on what I found out the weight would be of course:

3S SMC 9000mah 28C Battery
Castle or equivalent 2650Kv motor setup

Based on the calculations I ran through the RC Calculator:

http://scriptasylum.com/rc_speed/_top_speed.html

The RPMs the motor would be seeing would be 29415RPM which isn't too much different than a 4S Neu 2050 setup I have used before of 30340RPM

The battery has a continous rating of 252Amps, which should be more than enough to handle the motor and spikes. It also has a stored energy of:

9Ah x 11.1V = 99.9W

more than even a 5S 5000mah setup or my 4S 6000mah setup. of course, 5S is more efficient! but, for the runtimes I need, it should be fine.

The main thing I am confused on is I have seen and done caculations that show a higher amp draw as the voltage drops to cutoff, but got a message that this is incorrect. Anyone know why this is? others have posted these kind of calculations too of Motor estimated Wattage divided by given voltage at a certain time to determine estimated amp draw.


Next, based on the info on what I am looking at trying, other than the obivous efficiency of more voltage, etc. What problem would I have doing this based on the specs I listed?

Waiting right now to see what SMC says the battery pack weight will be.

It has been reported on rctech that someone else has run a 3S setup with the 2650kv with the vehicle I am looking to put it in (Hyper 9E) successfully, so curious about this.

[brushlessboy16]

I ran 3s2p 4000mah zippy flightmax packs on a hyper7 this past weekend with the cc 2650. Ran cool and the higher mah and amp rating easily handled the 15 minute mains and the packs didnt go pask 90 degrees.
You need to gear to compensate the lower voltage.. Just make sure your packs are rated for lots of amps.

[nitrostarter]

I run the 2650 combo on 3s1p 4900 and 5000mah packs in my Jammin X1 buggy. She runs flawlessly, with good temps, for a good 13 minutes. I'm geared 15/48 right now and theres plenty of speed for the track.

[Cain]

for me the gearing would appear to be 1 tooth higher than what I would do on my Neu 1512 2.5D/F motor. I don't think Amp draw should be an issue with the 9000mah pack at 252Amps continous.

[lincpimp]

The speed control will take more load, but if you plan to use the MMM I am sure it will be fine.

Any reason you want to run a 3s setup like that? Given the battery size and weight you suggest I would say that it would be better to run a 4 or 5s setup with a similar weight lower mah battery and a lower kv motor?

On the other hand your setup may be a little cheaper than what I suggested, not sure what the 3s 9000 battery costs, but it may be cheaper than a 4-5pack (not a zippy but most likely cheaper than an enerland based pack). Plus CC only offer the 2 motors, and for 40k rpm the 2650 on 3s is about the only way to get that.

Whatever, your setup should work fine.

[Cain]

So far I have been happy with Castle's stuff and there customer service, so i figure if I get all my stuff with them, good to go there. I also found a really good deal on the 2650 setup, about $225. I wouldn't mind having everything serviced through them instead of the Neu having to go through Neumotors direct. The 2650 fits the bill for a 3S setup at that price. I could also sell my current RC8 setup with the Neu to someone local so they can join in on the class.

The main thing I am confused on is I have seen and done caculations that show a higher amp draw as the voltage drops to cutoff, but got a message that this is incorrect. Anyone know why this is? others have posted these kind of calculations too of Motor estimated Wattage divided by given voltage at a certain time to determine estimated amp draw.

I would say to get the same speed, yes your amp draw will go up, as your voltage goes down. Just like running a lower voltage battery, amps goes up to mantain same speed. But if you compare full throttle to full throttle, as the voltage drops the amps will go down, since your voltage and amps increase porportionally to your gearing. Just like on the same gearing 4s will pull more amps then 3s will.
I'll say this, those batteries , or the MMM 2200 have no problems with 60 on 4s in an E-revo, so I would think the 2650 on 3s would be great in your situation.

[rootar]

you gotta think though your getting no plausable advantages because an equvilant lipo to a 3s 9000 would be a 6s 4500.... and the weight and size will be the same also so really your just getting a big battery to give you longer runtime. weather its a 3s 9000 or a 6s 4500 they are both large and equal in their weight/power, you know that 6s is more effiecent but if your on a smaller rack than 3s should work fine, BUT your extra runtime is only due to the lipo weight/power avaible.....

just the same as we run 6s 2500 lipos in josh's mp9 you coul run 3s 5000 in it with a 2650 motto instead of the 1350 motor, only the 6s works better and runs cooler on our larger, faster tracks.