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WHO CAN EXPLAIN ME? (about esc,motor,battery)
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kikay00 View Drop Down
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Posts: 3 		  Quote kikay00 Quote  Post ReplyReply Direct Link To This Post Topic: WHO CAN EXPLAIN ME? (about esc,motor,battery)
    Posted: 18/May/2010 at 8:59am
Hi im new in this hobby , and i want to someone explain me what about with the esc, battery and the motor.

how can i know if the esc goes with the motor and if the esc goes with the battery

for Example:

-What happen's if i have a battery of 80 Ampers ( 4,000 mah ,20 c) and connect to a esc of 40 ampers , and then to a motor of 30 ampers.

- what happen's if i have a battery of 40 ampers (2,000 mah, 20 c) and coonect to a esc of 80 ampers , and the to a motor of 40 ampers.

i want to know about the relation they nees to have to combine , ESC , Battery and Motor .

-if a battery with more ampers than esc supports , can burn off

- or if a esc that supports more ampers than the battery and the motor  nothing happens

thats my all questions about
i want to know how can i combine all these 3 things

thanks to all , and sorry for my english im from mexico :P
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Burnaby View Drop Down
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Posts: 944 		  Quote Burnaby Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 10:08am
Simple answer is Battery > ESC > Motor to prevent burn out. The closer the match, the better the efficiency. Google basic electricity and electronics principles.
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kikay00 View Drop Down
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Posts: 3 		  Quote kikay00 Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 10:21am
thanks for answer , but i mean what happens if i plug a battery of 40 ampers in a esc of 80 ampers and motor of 40 ampers , nothing happen?  gonna be work? and vice versa with the battery of 80 ampers and esc of 80 and motor of 40 ? what happens
thanks
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Posts: 1956 		  Quote Mustang Sally Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 10:26am
Go to:
A minimal technical knowledge is required for this hobby; please ensure you know the differences between up and down.
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kikay00 View Drop Down
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Posts: 3 		  Quote kikay00 Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 11:00am
nothing there 
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what_the?! View Drop Down
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Posts: 50 		  Quote what_the?! Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 11:10am
Originally posted by Burnaby

Simple answer is Battery > ESC > Motor to prevent burn out. The closer the match, the better the efficiency. Google basic electricity and electronics principles.


err no.

whilst you are correct that Battery>ESC>Motor- the closeness of match does not improve efficiency.

for the highest efficiency, each component needs to run with as much overhead as possible.

So, lets say you have a prop that draws 20A at a certain rpm on a certain motor.

if you have a motor that can handle 15A, then it will be inefficient and probably wont last long due to heat.

a 20A motor will generate plenty of heat too- and wont last too long either, but will last alot longer than the 15A motor.

A 30A motor will be able to handle the 20A for a long long time. A 100A motor will last virtually forever, but will be far too large and is overkill.

Now, the same applies for the ESC. a 100A ESC is too big. A 30A, or even 40A ESC will handle the 20A load fine.

For the battery- it is only to do with the load that the motor is drawing..i.e in this case the 20A.

IF you use a 2000mah battery then it needs to discharge at "10C". This is calculated by taking  the power draw from the motor (20A), then dividing by the mah of the battery (2000) divided by 1000 (which equals 2).

i.e. 20A/(2000/1000) = 10.

Now, 10C means that you will get 60minutes/10C = 6 minutes of flight - if that is your average current draw.

Some batteries are rated as capable of 40C. i.e. capable of discharging their entire energy in 60minutes/40C = approx 1.5 minutes.

40C, for a 2000mah battery equals 40 x (2000/1000) = 80Amps.

so in other words the battery can discharge 80A continuous for 1.5 minutes.

generally, the higher you stress your battery, the less life itll have.

so even though a cell may be able to discharge at 40C- dont expect lots of cycles out of it.

a good rule of thumb is to work at around 10C-15C. so if you expect to draw 20A, pick a 2000mah, or 3000mah battery that is capable of 10C discharge minimum.

If you want your system to be really efficient, go for as large a battery as you can. The more overhead it has, the less internal resistance, so less heat, more cycles etc.

hope this helps.
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Posts: 868 		  Quote Phrozius Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 11:31am

If your new to the hobby my single best piece of advise is to invest in a watt meter such as:

 

http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=6553

 

This watt meter is one of the most valuable tools in my shed. 

 

Its a balancing act. But in general you can not have an ESC that is too powerful. The disadvantage of an over rated ESC or a battery that is larger than needed is due to size and weight. Weight is an electric flyers no.1 enemy.

 

A motor will only draw the power it needs. However AMP draw is dependant on load (how big the prop is). Also take in to account voltage. Is the motor and ESC rated to the voltage you want to use? (how many cell lipo can the motor/esc accept)

 

It's best to over rate slightly. Say your motor draws 25 amps use an ESC than can handle 30 to 35 AMPS and then a battery that can handle 35-40amps. This is optimal and you will find everything runs cool. If anything is getting excessively hot you’re loosing energy through heat and wasting power. Excessive heat will also lead to deterioration of the component. While doing this you also need to consider how much weight your adding, how it will effect the COG etc etc.. as I said a balancing act.

 

Example 1:

 

You have a 2200mah 3cell 20c (44amp max) you use an 80 amp ESC and use a motor that has a max amp rating of say 30 amp with a suggested prop size of say 11x5" (just an example) so lets say you put this setup on your watt meter and discover that at WOT it draw 27amps. In this case the Motor, ESC and Battery are all working at or below their rating so all will be fine. If you put a bigger prop on and find it is now drawing 32amps you have exceeded the rating of the motor but not the battery or the ESC (this will be apparent as the motor will get warm)

 

Example 2:

 

2200mah 3cell 20c (44AMP), 25amp ESC and motor rated to 30amp. You use the suggested prop and run it on your watt meter. You find the motor draws between 25 to 30 amps and the ESC is getting very warm. In this case your exceeding the ESC rating and will most likely burn it out if you continue. How ever you use a smaller prop and run it again to find your now drawing 22amps and this is ok.

 

Example 3:

 

1500mah 3cell 20c (30amp) 40amp ESC motor rated to 40 amp with suggested prop. You run it on your watt meter and find at WOT the motor draws 36amp. This time you have exceeded the battery rating and the battery will become warm and deteriorate.

 
Hope that makes it easy to understand.. and again I can not stress the value of a watt meter enough. Don't guess.. check!
 
NOTE: WOT = wide open throttle


Edited by Phrozius - 18/May/2010 at 11:55am
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Burnaby View Drop Down
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Posts: 944 		  Quote Burnaby Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 11:36am
what_the?!>  Sound like you're discussing durability, I was talking about efficiency. Electric Motors & ESC have efficiency curves typically rated near their peak, say in the 80-90% range. Going below waste energy with increased wear. A bigger battery will be less stressed at the cost of weight (which reduces efficiency).

I set up my heli motor, ESC and battery around the max for optimal efficiency. Don't know enough to comment on props efficiency.
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Posts: 50 		  Quote what_the?! Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 12:15pm
Originally posted by Burnaby

what_the?!>  Sound like you're discussing durability, I was talking about efficiency. Electric Motors & ESC have efficiency curves typically rated near their peak, say in the 80-90% range. Going below waste energy with increased wear. A bigger battery will be less stressed at the cost of weight (which reduces efficiency).

I set up my heli motor, ESC and battery around the max for optimal efficiency. Don't know enough to comment on props efficiency.


well yes that's true also....but i left it out as i thought it might be too complex a concept at this point.

but yes, ESCs and Motors run at about optimal efficiency at around 80% of max load...but remember that it is a relative measure, and a 100A ESC running at 20A will not be at its max efficiency but will still lose less absolute heat than, say, a 30A ESC...simply because its larger.
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Posts: 50 		  Quote what_the?! Quote  Post ReplyReply Direct Link To This Post Posted: 18/May/2010 at 12:17pm
PS theres some good posting here!..nice one guys!
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