Madaboutrc

Hi guys, I'm new to the rc world and im having trouble understanding the whole "what battery goes with what esc and motor"

I have a hsp 1/10 electric on road car which came with a 3300kv brushless motor in it and an esc which I'm unsure of the specs ( also came with a 7.2v 2000mah battery) What I'm trying to work out is the science behind what battery and esc can be used with my motor. My understanding so far is that a motor draws a certain amount of amps and that your esc needs to be of a rating at least equal to that, but what battery can I use???? Can I use any size battery with any c rating as long as its the right voltage???

I think my motor draws 45A and I think it has a 45A esc... Can I use say a 5000mah (20C) battery?


Thanks heeps

ThePanda

iTrader: (68)

ok easy way to calculate battery "c" rating. take the capacity and devide by 1000. this will give you one "c"( there is actually a different way to do it that makes sense mathmatically but i forgot it lol) so lets do the maths. a 5000 mah battery with a 20 "c" rating 5000/1000: 5: 1"c" so 5*20 "c" :100 amps. so the battery you have can probably deliver 100amps con.

here is another example a 7500mah battery with a 90 c rating will give 675 amps con, cuz (7500/1000):7.5 then (7.5*90):675

usually batterys may have a burst c rating meaning if the 5000mah had a con of 20c it might have a burst of 30c or 40c theoretically it would say on the battery.

ok now the motor. motors draw amps when spinning under load. the amps that the motor draws fluctuates when driving depending on how much throttle you give and how hard the motor is working the amps for the motor are supplied by the esc. say the motor is drawing 90 amps peak- then you need an esc that is able to supply 90 amps.so then you might want a 120 amp esc. you want htere to be a difference in the motor draw and the esc capability otherwise you will have heat issues as the esc is opperating at peak already.

Madaboutrc

Awesome thanks for the reply, so am I right in saying that your esc needs to be of a higher amperage than your motors draw, and that you can use any battery that has suffients out put?

Ie, motor draws 43 amps esc is 60A battery needs to be at least 43A output?

Motor=43A, esc =60A, battery = 80A (4000mah at 20c) is this set up ok???

Cheers, massive noob

ThePanda

iTrader: (68)

Yes the esc needs to be able to put out more amps than te motor can draw. Yes the setup you have is good.

Madaboutrc

Thanks heels for you help mate, would appreciate any more info any1 has to give : )

theblitzkidd

iTrader: (11)

I would recommend a 5000mah 20c lipo, that way u have good capacity and a decent discharge rate just an opinion

Madaboutrc

Can the battery be caplable of putting out more power than the esc is rated to.

Example, if I used a 4000mah (30c) =120A output with a 60A ESC would that be good or bad?

I've been told that would fry my ESC???

Banshee8530

iTrader: (1)

A Battery's C rating is only an indicator of internal resistance. If you have a battery with a high C rating, it will be more capable of supplying large current, but that current is dictated by the ESC and motor. The battery only gives what is demanded of it. The only time a high C rating is necessary is for racing in classes like 4wd SC, mod TC, etc where current draw is huge. Some Spec classes draw large currents too. So a large C rating will help, but the only thing it hurts is the pocket book. If your C rating is low, like 20C, you will just be slower; so long as the basic set-up rules mentioned above have been met.

On another note, you said your car came with a 7.2V 2000 mAh battery. That is a NiMH battery. The batteries that are C rated are Li-Poly. Do you know if your ESC is Li-Poly compatible, i.e. does it have Low voltage cutoff settings? Without this crucial function I would not run Li-Poly.