Using capacitors instead of batteries on RC airplane???

[trOver]

Has anyone tried this before? What kind of capacitor is used to actually POWER the motor, not smooth out interferences from the motor? All the capacitors that I have seen on towerhobbies, etc, have been motor accessories.

Also, mF is micro farad, am I correct?

What fraction of a farad would be equivilant to say a 2ah battery at 7.2 v?

Thanks

 

[JohnCU]

Originally posted by: trOver
Has anyone tried this before? What kind of capacitor is used to actually POWER the motor, not smooth out interferences from the motor? All the capacitors that I have seen on towerhobbies, etc, have been motor accessories.

Also, mF is micro farad, am I correct?

What fraction of a farad would be equivilant to say a 2ah battery at 7.2 v?

Thanks

you do know the capacitor is empty of energy once it's used up the first time unless you recharge it, right? unless you want an ultracapacitor.

 

[AgentJean]

Ok, I never took electronics in high school or college but isn't a battery just a glorified capacitors?

 

[Oscar1613]

1100F

 

[JohnCU]

Originally posted by: AgentJean
Ok, I never took electronics in high school or college but isn't a battery just a glorified capacitors?

No, a capacitor uses an electric field to store energy, while a inductor uses a magnetic field to story energy, a battery uses a chemical reaction.

C=eA/d

 

[spidey07]

one thing you're forgetting - weight.

 

[trOver]

Originally posted by: JohnCU

Originally posted by: trOver
Has anyone tried this before? What kind of capacitor is used to actually POWER the motor, not smooth out interferences from the motor? All the capacitors that I have seen on towerhobbies, etc, have been motor accessories.

Also, mF is micro farad, am I correct?

What fraction of a farad would be equivilant to say a 2ah battery at 7.2 v?

Thanks

you do know the capacitor is empty of energy once it's used up the first time unless you recharge it, right? unless you want an ultracapacitor.

Yes i know this, I am just looking for a really light way to power an airplane. I realize you can charge them with any voltage (up too rating) and you charge them using a bigger battery, ex. car battery, etc

 

[trOver]

You think the # of capacitors equivilant to the battery I stated above would be more weight than a reg. battery? (li-ion

 

[JohnCU]

Originally posted by: trOver

Originally posted by: JohnCU

Originally posted by: trOver
Has anyone tried this before? What kind of capacitor is used to actually POWER the motor, not smooth out interferences from the motor? All the capacitors that I have seen on towerhobbies, etc, have been motor accessories.

Also, mF is micro farad, am I correct?

What fraction of a farad would be equivilant to say a 2ah battery at 7.2 v?

Thanks

you do know the capacitor is empty of energy once it's used up the first time unless you recharge it, right? unless you want an ultracapacitor.

Yes i know this, I am just looking for a really light way to power an airplane. I realize you can charge them with any voltage (up too rating) and you charge them using a bigger battery, ex. car battery, etc

yes but a 1F capacitor is huge, you need ultracapacitors for this, and I've only seen this in a magazine article before.

 

[Jeff7]

As far as I know, NiMH or Li-ion have higher energy densities than capacitors, which is why the former are traditionally used for places requiring any decent level of power storage.

Originally posted by: JohnCU

Originally posted by: AgentJean
Ok, I never took electronics in high school or college but isn't a battery just a glorified capacitors?

No, a capacitor uses an electric field to store energy, while a inductor uses a magnetic field to story energy, a battery uses a chemical reaction.

C=eA/d

When did AgentJean say anything about inductors?

Originally posted by: JohnCU
yes but a 1F capacitor is huge, you need ultracapacitors for this, and I've only seen this in a magazine article before.

1F capacitor
$3.50. 0.143 cubic inches.

Still, that's not a whole lot of power. It might power a cellphone vibrator motor for a few tens of seconds.

 

[trOver]

Originally posted by: JohnCU

Originally posted by: trOver

Originally posted by: JohnCU

Originally posted by: trOver
Has anyone tried this before? What kind of capacitor is used to actually POWER the motor, not smooth out interferences from the motor? All the capacitors that I have seen on towerhobbies, etc, have been motor accessories.

Also, mF is micro farad, am I correct?

What fraction of a farad would be equivilant to say a 2ah battery at 7.2 v?

Thanks

you do know the capacitor is empty of energy once it's used up the first time unless you recharge it, right? unless you want an ultracapacitor.

Yes i know this, I am just looking for a really light way to power an airplane. I realize you can charge them with any voltage (up too rating) and you charge them using a bigger battery, ex. car battery, etc

yes but a 1F capacitor is huge, you need ultracapacitors for this, and I've only seen this in a magazine article before.

You really think I will need 1F?

 

[Oscar1613]

Originally posted by: Oscar1613
1100F

of these

 

[Oscar1613]

F = A-s/V

 

[CaptainGoodnight]

Originally posted by: trOver
Also, mF is micro farad, am I correct?

a micro farad is written as: µF

mF is a milli-farad

 

[JohnCU]

Originally posted by: trOver

Originally posted by: JohnCU

Originally posted by: trOver

Originally posted by: JohnCU

Originally posted by: trOver
Has anyone tried this before? What kind of capacitor is used to actually POWER the motor, not smooth out interferences from the motor? All the capacitors that I have seen on towerhobbies, etc, have been motor accessories.

Also, mF is micro farad, am I correct?

What fraction of a farad would be equivilant to say a 2ah battery at 7.2 v?

Thanks

you do know the capacitor is empty of energy once it's used up the first time unless you recharge it, right? unless you want an ultracapacitor.

Yes i know this, I am just looking for a really light way to power an airplane. I realize you can charge them with any voltage (up too rating) and you charge them using a bigger battery, ex. car battery, etc

yes but a 1F capacitor is huge, you need ultracapacitors for this, and I've only seen this in a magazine article before.

You really think I will need 1F?

i'm not sure, i haven't done basic circuits in a while, but if you were powering a pure RC network, you'd have to work out the time constant and all that I would imagine.

or the energy, E=.5CV^2

 

[JohnCU]

how long do you need to run it?

 

[PottedMeat]

Why not just use a stack of those Lithium Ion polymer batteries - the electronics goldmine used to have some 3.7V 1100mAh capacity ones a while back for $1 each. They're designed to be thin & lightweight. How are you going to get sustained power output with a capacitor? You may be able to charge and dump power very quickly, but I dont think you can store it for very long. Generally with higher capacitance the working voltage rating goes down and the weight goes up.

 

[trOver]

around a min.?

 

[halik]

haha you fail at physics - unless you get one of those car audio capacits, you won't have enough current to power anything for more than couple secs.

 

[bignateyk]

This thread makes the baby jesus cry.