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 BRUSHLESS....CHOICES PLEASE.

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nhp651
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nhp651

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PostSubject: BRUSHLESS....CHOICES PLEASE.   BRUSHLESS....CHOICES PLEASE. EmptySun Feb 24, 2019 8:31 pm

Right guys...……...I don't need reams and reams of choices...…...I won't understand as i'm an electraphobe……….but the speedline 1;12 Shannon comes with these motors......outrunners I believe as the can on the outside rotates...…


BRUSHLESS....CHOICES PLEASE. Img_1610


BRUSHLESS....CHOICES PLEASE. Img_1611


BRUSHLESS....CHOICES PLEASE. Img_1612


simple answers to simple questions please;

1] what one way [no reverse] ESC should I buy.

2] what batteries should I buy, 2s,3s 4s...……..[god knows what they mean], and do I have one pack per motor,.... and do I need different chargers to my normal nihms and sealed cell batteries that I use with brushed motors.

3] what is the cycle for these lipo batteries...……….do you run them to flat, or can you charge them after each run.

4] do I run the receiver off a separate 4 cell battery pack as normal without bec.


5] and finally is there any fire risk to leaving these batteries on charge unattended.


please, very simple answers, and no arguments...….


these questions were asked by someone on mayhem, and god knows how many different answers there were...…...and I was totally baffled by all the different answers and arguments, making it extremely difficult for thick sods like me.


simple explanations please as I truly DO NOT  understand electrics or electronics...……….I can understand how an automatic gear box on a motor works...……..but I am useless with this sort of stuff.


thank you in anticipation for clear basic shopping list.
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PostSubject: Re: BRUSHLESS....CHOICES PLEASE.   BRUSHLESS....CHOICES PLEASE. EmptyMon Feb 25, 2019 9:56 am

First up yes those are outrunners you have, and a very similar spec to the ones i usually recommend to people (they are also my go to brand for a decent motor that do not fail! (overland thumpers) 


1] what one way [no reverse] ESC should I buy.




depending on the brushless Draw rates it could be as little as 20amp up to 400amp!


however after a quick google of your motor this is the spec that turned up...


Model: NTM Prop Drive Series 35-42A 1250Kv
Kv: 1250rpm/v
Turns: 6
Max current: 56
Max Power: 500W @ 12v (3S) / 600W @ 15v (4S)
Shaft: 4mm
Weight: 148g
ESC: 60A
Cell count: 3s~4s Lipoly
Bolt holes: 18.9mm & 25mm
Bolt thread: M3
Suggested Prop: Prop test data coming soon!





So at least a 60 amp esc per motor is required!   ( i would recommend going for at least 80amp to be on the safe side as im taking those values at face value from hobby king!)




2] what batteries should I buy, 2s,3s 4s...……..[god knows what they mean], and do I have one pack per motor,.... and do I need different chargers to my normal nihms and sealed cell batteries that I use with brushed motors.


NOTE:- 


you will require 1 battery per motor per ESC .. you cannot use 1 battery to power two ESC's/motors in this instance ( its not a drone,) the batterys are rated to discharge at some set 'C rates' using one battery to power more than one motor will = FIRE


You can run NHMI batteys if you wish.... depending on the discarge rate of the nhmi, which for this size motor you need at least 50c


this however is overshadowed by cost as lipos are cheaper when you need batterys with a 50c discharge rate as most lipos come as standard at 20c 30c and 50c!


2s 3s 4s = the S stands for how many cells the battery has a 2s lipo has 2 cells, a 3s has 3 cells and a 4s has 4 cells Each cell within the pack is 3.7v (hence why we need a charger with balance)



However if we ignore the fact that you wont be using NHMI for this model and motor setup ( unless you have a spare £70 laying around for two batterys) then your options on batterys will be down to the RPM you wish to achieve...


2s lipo is 7.4v
3s lipo is 11.1v 
4s lipo is 14.8v


I've written this post so many times in the past now its old hand info however .. heres the maths..


Motor KV x Voltage imput = NO Load RPM 


(larger prop size (over 45mm) will draw more amps so hence my earlier suggestion on a larger esc)


your motors are 1250KV... 


1250 x 7.4  = 9250 RPM 
1250 x 11.1 = 13,875 RPM
1250 x 14.8  = 18,500 RPM


Going of what sort of model this is..... and my usual recommendation for twin motor systems.... then a 3s Lipo would achieve very decent results!


the 4s is very high speed especially when you have 2 motors going, however you using an outrunner motor so it has a lot of torque ( outrunners for torque inrunners for high speed RPM) 


The price jump from 3s to 4s is also vastly different!




As for a charger , yes you will need to purchase a LIPO charger & balance system these are NOT expensive anymore! but expect to pay £20-30 for a reasonable one!!!




3] what is the cycle for these lipo batteries...……….do you run them to flat, or can you charge them after each run.



Tricky to answer.... in the old days you used to run until your little alarm let you know the battery was dead and needed charging ( or it unbalances the cells and kills the battery) 


this is still somewhat a golden rule, however the technology has improved dramatically in recent years so the batterys tend to be able to take a bit more abuse.. however a decent ESC will auto stop your model momentarily when the battery is at its im about to die moment, then allowing you a few mins to get back to shore... however the cheap chinese esc's dont do that....  so you will have to watch the drop in speed to know your on your way out... 


in all fairness do not expect to get more than 15-20 mins of a 3s lipo ( however each battery is different so it will be a little trial and error, but thankfully as brusless motors are 99% efficient the slow down in speed when the batterys are going, is noticeable and still able to provide you with up to a further 5-10 mins of run time just as a much lower discharge rate!


as for charging after a run.... yes you can take your little lipo charger.. plug it into your cars lighter output and charge on the go!
when i used to go racing (mono 1) i took a car battery with me as part of my charging station... and some clubs had a lorrys battery setup for everyone use!!!!




4] do I run the receiver off a separate 4 cell battery pack as normal without bec.





Depends on the ESC!!! mostly the answer is no .. ESc's have built in BEC's as standard!, just be sure to disconect one BEC if using two ESCs! 
you know what happens after that!!


However that said.. if you ave space and dont mind a battery pig.. there is no reason to not disconnect both ESC's BECS and run your receiver off
a separate 6v pack... however the draw back is that pack is running everything else, including your servos! ( maybe if you go this way run a 6V LA ) 




5] and finally is there any fire risk to leaving these batteries on charge unattended.


YES & NO!


YES if you do not charge your batterys in a charging bag/box 


NO if you do but keep and eye!


any cell that is damage could cause a fire regardless of how secure it is.. things to watch for are swollen Lipos backs. ( trust me you  would notice em) a swollen pack is a bin ASAP job.. that babys about to go boom!

and be sure to check for damage through knocks and drops! 

my method of charging is very simple!.... i have a Ammo box ( army surplus store, £20) i took a little chunk out of the top of the box next to the hinge to allow the cables to pass into the box, and then i just dump the batterys in, dump the lot on the concrete floor, connect up and let the charger do the job...

''Tankful'' iv'e not had a fire to test if this box works however if it works to stop ammo exploding, so a lipo fire sure!!!




Aron

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PostSubject: Re: BRUSHLESS....CHOICES PLEASE.   BRUSHLESS....CHOICES PLEASE. EmptyMon Feb 25, 2019 10:33 am

Recommendations for your setup...


ESC's;-

80 amp with reverse!

here

or 80 amp with water cooling ( i would pick this option personally!)

here

Lipos;-

zop power 3s 50c 5200mah  on a XT60 PLUG 

here

Charger options:-

here

these are just a reasonable priced items that fit within my recommendations... i do encourage you to look around too as i literally just googled this lot and had a quick scan on prices and specs! ( usually i would spend hours looking! not 15 mins)

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nhp651
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PostSubject: Re: BRUSHLESS....CHOICES PLEASE.   BRUSHLESS....CHOICES PLEASE. EmptyMon Feb 25, 2019 10:42 am

that was great expose, Aron...……..and most grateful, and easy to understand...…...its for my Shannon lifeboat i'm building...….if I were to use 4s lipos but at lower revs, [as I have seen these models going flat out on 4s which is grossly above any flat out scale speed] will I get longer running time than reaching the flat out speed on 3s which is just above scale speed.....

thanks aron, you have made things a lot clearer too me.....and once I get the boats back from Dave[Stavros] from spraying up, I shall be buying...……..now

the question is.....who do I buy this gear from...……..i'm not of the frame of mind that cheap and cheerful is best.....you get what you pay for...….and if you are equipping a model that costs well over a grand, why skimp on what makes it go,


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PostSubject: Re: BRUSHLESS....CHOICES PLEASE.   BRUSHLESS....CHOICES PLEASE. EmptyMon Feb 25, 2019 11:00 am

Truthfully..

i usually pick a branded named item() that has a good reputation.. however when it comes to water cooled esc's i tend to just find one that isnt a stupid price!

Water cooled ESCs are a harder find so when i go find them its usualy that one i go with, ive been lucky that hobbywing do most 30 amp water cooled esc's for my boats ( i dont go higher than that, when i use an over lander thumper motor) so ive been able to get loads over the years without issues, however going higher that 30 amps like my dad dose requires the shrug of the sholders and ebay! hes been lucky and brought several 80-120amp water cooled esc for £11 .. they dont live long ( usually 2 seasons) however for £11 its hard to knock that return!

its entirely up to you with what you go with just be sure to check and recheck that what your buying is suited to your needs as a mistake can be costly!

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