11v or 14v.... What difference does it make?

[noguy]

Hello,
I am purchasing a use trex 450 & I am in the market for some batteries.
I see some folks are flying with 4S packs and I am wondering what the higher voltage does for flight performance?
Is the standard RCE-BL35G/430L setup OK @ 14v?
The esc specs say its ok but I cant find any info on the 430L.
Does the higher voltage give better efficiency, flight time, peak power?
I understand a 14v 2000mah will yeald a higher watt rating than a 11v/2000mah, so I think this means higher peak power. What other power & performance characteristics are affected by choosing a higher voltage pack?

Sorry for my electronic ignorance! Noah

[cholyoake]

higher voltage would mean the motor would spin faster, so a 3500kv motor on 11v will spin at 38,500 rpm with no load, on 14v it will spin at 49,000 rpm with no load. that would mean higher headspeed. to compensate for that you would use a smaller pinion on the motor.
another thing, if a t-rex on 11v needs about 12 amps to hover (i don't know how accurate that is, its just an example) that would be 132 watts. with 14v, it would only need 9.4 amps to make 132 watts, so you will have longer flight times.

there are other diffrences aswell, but thats all i know about.

[noguy]

Ok so I think I am catching on here... a 11v 2200mah pack is like 24 stored watts
and a 14v 2200mah pack is like 30 stored watts of power.

Is one a more efficient setup than the other?

Ok Im looking at TP batt specs here. Which are as follows for the 2200mAh packs.
2200 @ 11.1V weighs 170g & the 2200 @ 14.8v weighs 218g.
If 2.2ah*11.1v= 24.4w & 2.2*14.8= 32.6w
Then 170g/24.4w= 7grams per watt for the 3s
& 218g/32.6w= 6.7grams per watt for the 4s

Why are more people not flying the 4s packs. Is this too much extra weight?
I figure the extra 48grams is about 5-6% weight gain for the average 750g 450 heli. While the extra 8watt gain is about 33% added power to the 3s pack.

So again I am confused if people can add 6% weight and gain 33% power why arent they. can the motor not handle the extra rpms?....
I am very confused. I would like to invest in about 5 batts this week & unless I am totally missing something it seems like a no brainer to fly 4s packs.

Anyone out there flying 4s packs please let me know what you think.

Thank You, Noah

[busted blade]

i have used and tested 3,4, and 6s setups in my trex 450's. first if you are really into getting any power setup dialed in right then buy a onboard data logger such as the eagle tree micro power. its the only way youre going to really know whats going on. second, if you go 4s over 3 the amp draw can be considerabley less as stated above. what this means is that you dont have to run the high "c" rating battery. the tp prolites are fine (about the same weight as the high "c" 3s). but if your setup is wrong, pinion, pitch, etc., you can still make the 4s draw alot of amps. off the top of my head without going back and looking at data files a powerful 3s will peak at 35-40amps, 4s (more powerful) will pull about 30 amps, and my 6s (zero bog with 14deg pitch at 2800 hs) pulls 6amps at hover and 22amps at full load. the 6s is really overkill though plus the hassle of managing 2 paks in series. check out trextunning .com for some good 3 and 4s data

[noguy]

busted blade, Thanks a bunch man. You are a huge help.

Do you have any motor sugestions for a 4s setup? I would imagine I should have one intended to run at the higher rpms.
Or does one simply buy a lower kv rated motor to keep the motor rpms down and gear for desired head speed?

It seems to me that for the little extra batt $. You will get longer flight times and electronics(mainly batts) that are less stressed.

Noah

[busted blade]

Noah, i only used the medusa 2500kv with the 4s. i based that off of info on trex tunning. yes you do want a lower kv motor for the reasons you described.

[noguy]

Yes I found the motor article on 4s systems @ trextuning. Great info!

[noguy]

Busted Blade, I read all over trex tuning and decided to go with a 4s setup. My deal on the used rex fell through so I decided to try out the Mini Titan. I am almost done with assembly. I am going with the justgoFly 450th motor reviewed @ trextuning. I chose it for it being 2nd place in amp draw (only 22amps @ full thro/pitch) and it is the lightest motor out there, also its price is about half of most others. I went wih a CC pheonix 35a esc & a medusa 3a bec. I havent ordered any packs yet.
I am still trying to decide between the hextronics 4s (unbeatable price) & the TP prolites 4s (unbeatable weight). I just dont know really how bad the 239g weight of the hextronix pack really is. I think it will be OK as my goal is long flight times and not extreme 3D.

The TP 4s 2100 15c is 178g & is $99
and hxt 4s 2200 20c is 239g & is $43 a $56 difference & a 60g difference.

I am hoping that this will be offset by the 57g motor weight, which is almost half of the weight of the other good 4s motors. (~100g)

Any general input on this setup would be appriciated and opinions on the batteries would also be appriciated.

Thanks, Noah

[noguy]

Ok gang.... Thank you all for the guidance. I have started testing out the 4s setup on my mini titan. I think I am going to like the high volt route. I havent spooled up under any load yet but @ zero pitch with 2600rpm headspeed I am only drawing around 8amps :D :D :D With the new light weight packs that are out I dont see why everyone is not running 4s in there 450's.

A TP Prolite 4s 2000mAh pack is only 160g.... & capable of 24amp continuous
I dont think my setup will even peak at that under full load and with a even higher headspeed..

Most of the high discharge packs guys are flying are a heavier setup and really give all of the electronics a workout.

my .02 Noah

[busted blade]

have fun noguy. the greatest thing you may notice about the added power is it can save you from crashing sometimes. a typical 3s senario is: you get out of wack, panic, go to full pitch, drag the head/tail down, tail swings around, cyclic gets spongy, and down she goes. not the case with the high power :mrgreen:

[noguy]

Yeah busted I think I am gonna get what I was after.... Flight times. I have heard many are only getting 5-6 mins on the stock power train and 3s packs.

I just ran down another new cheapo hextroni 4s on the bench.
I started out at 14.8v (amount of charge they arrived in mailbox with) cutoff at 13v
Governed at 2500rpm, I held 2-4 degree of pitch most of the time a few 10degree held periods and some ramdom pitch pumping.
Max draw was 16.8amps and average was 8.8amps
rmps held well all of the way through. ESC WITH GOV'S RULE!!! :D :D :D
I had 9.5 minutes of run time before cutoff (with a nominally charged pack)
Something is wrong with the cum mAh on my ET recorder. It displayed while I was recording but data isnt there now??????

Temps were as follows:
battery 118F
esc 130F (on mosfet side) 140F (on other side)
uBEC 98F
motor 130F
and ET recorder was 110F

This was in 95F ambient temp... (my heatbox upstairs bonus room :arggg: )

I think I am even gonna get away with these $35 lipo's for a while. We'll see how many cycles they get though. :roll:

Busted blade I really want to thank you for your advice on the high volt stuff.
Most other people kept saying I would be a fool to run 4s.... I think I'm gonna have the last laugh when my heli is still flyin' well past 10 minutes. :lol:

Thanks again, Noah

[busted blade]

no problem. im glad i could offer something. on your "cumah", go to the upper left corner on your 2d graph and click on x-axis,y-axis, etc. and make sure the cumah is checked

[noguy]

I did this before and it would show a flat line with no data....00000 all the way across.....Dont know what was worng but it worked now when I reloaded the file.

[noguy]

Well a little update. The 4s has been going great for me. I get a good 10min flight time sport flying @ 2700rpms. I just purchased a FP EvoLite 4s pack that weighs 180grams.
That should be about a 70g weight loss for my bird and the packs are rated at 38 amps cont. giving plenty of headroom to not stress the pack.

I will post an update comparing the cheapo hextronixs packs to the evoLite when I can.
This should be about a 10% weight loss for the heli so I hope it is pretty noticable.