Higher Voltage or Higher Kv - RC-Monster Forums

LiqrSicc · **Higher Voltage or Higher Kv -** 10.01.2009, 02:49 PM

Ok guys I need somebody to school me on this. Let's say the motors I'm looking at have are capable of 60k RPM. I'm looking at 2 of them. One that has is 5000kv and one that is 2500kv. With the 5000kv I can run 3s (only capable of 12v max) to get about 55k RPM. With the 2500kv motor I can run 3s in series for 6s. At 6s it will reach the same RPM as the 5000kv motor. The dilemma is with the battery packs. I can run 2 3s 2000mah packs in parallel for a total of 4000mah. If I go the 6s route I'd have the same packs and run them series so I'd just have 2000mah. My question is since the 6s route will require less amps to achieve the 55k RPM does that also mean my 2000mah 6s setup will have close to the same runtime as the 3s 4000mah? Some somebody explain what advantages/disadvantages I'd have running the 6s setup over the 3s setup?

sabongi · 03:01 PM

Since when using 6S your electronics will run cooler and both setups have the same energy amount, you probably will get a longer runtime when using 6S if both setups weight the same :D

was i clear?

sabongi · 10.01.2009, 03:03 PM

AND since a lower kv motor is usually more efficient, 6S runtime will be better...

Arct1k · 10.01.2009, 03:05 PM

Generally volt up kv down BUT generally motors sweet pots is 30-35k...

60K is for speed runs only as a general guide...

2000-2200 kv 4s
1650-1850kv 5s
1300-1600kv 6s

LiqrSicc · 10.01.2009, 03:10 PM

Yeah pretty much for speed runs. With the same config my buddy gets about 15-20 minutes runtime with the 3s 4000mah 5000kv setup. Just wanted to make sure if I did the same thing with the 6s that I wouldnt get just a 7-10 minute run because I would be running the same packs but in series.

Finnster · 10.01.2009, 04:00 PM

Is this for a 1/10 scale or smaller? You can get away w/ running higher rpms on little motors, where a 5000kv motor for 1/8th scale is a deathwish (and 2500kv not so smart.)

Basically think of it like this, no matter which way you configure the packs, the total available energy stays the same. If you are drawing the same amt of power, the runtime has to be the same (ignoring eff losses.)

Ie
1s6P : 3.7v, 12000mah
6s1P: 22.2v, 2000mah
Both equal 44.4 Wh (watt hours: Amp Hours*volts)
If you draw 4.4Ah/min for your run, you end up with 10mins no matter what.

BrianG · 10.01.2009, 05:21 PM

Quote:

Originally Posted by Finnster

Is this for a 1/10 scale or smaller? You can get away w/ running higher rpms on little motors, where a 5000kv motor for 1/8th scale is a deathwish (and 2500kv not so smart.)

Basically think of it like this, no matter which way you configure the packs, the total available energy stays the same. If you are drawing the same amt of power, the runtime has to be the same (ignoring eff losses.)

Ie
1s6P : 3.7v, 12000mah
6s1P: 22.2v, 2000mah
Both equal 44.4 Wh (watt hours: Amp Hours*volts)
If you draw 4.4Ah/min for your run, you end up with 10mins no matter what.

+1. But I assume you meant 4.4Wh/min (bold above).

Anyway, even though the 6s1p and 1s6p configs have the same Wh value, running the higher voltage on a low kv motor will be more efficient. High currents create heat, which in turns to voltage drops, which means more power is being eaten up as heat for nothing. (This last part is to the OP, not you Finn)