Hi (it's me again 
)
I wanted to upgrade a little RC car so it'd become more powerful . I did think about using 9v motors but 1- they didn't fit there
2- the power source isn't powerful enough 3- the stock motor was "stuck" on the "gearbox" (differential ?) so it was hard .
So I came up with these 2 ideas .
1- use better batteries - The car has 3.6 v 600 mAh but I have a 7.2 v 500mAh which is lighter , so I'd rather use THAT .
2- change capacitors - usually there is a capacitor that "connects" the 2 pins of the motors (I've heard they say it's for "increasing torque" - makes no sense - at least to me ; although I did try it and I suppose it DOES make a difference !) , so I came up with this fiendishly clever idea to use different capacitors , there were "code 104" "ceramic" capacitors which I think is supposedly 100 nanoFarads .
So I had some questions :
1- Is it OK to do these ?
2- What capacitor is BETTER to put there ?
Thanks in advance !!
have you considered
- removing weight from the device (if possible)?
- add wheels with bigger diameter?
I suppose it DOES make a difference
What kind of test did you use to quantify what difference it made? For example, at the very least use a stopwatch to test how long it takes the vehicle travel 10ft from a standing start. For each capacitor value, repeat the test 5 times and take the average (to reduce sampling error).
I'm skeptical that the capacitor increases torque to any significant degree, especially such a tiny capacitor as one in the nanoFarad range. Actually, a very large capacitor across both brushed motor terminals would hurt acceleration from a standing start, as some of the current that would have been turning the motor is diverted to charging the capacitor. Only once the capacitor had charged to battery voltage would all the available current be available to the motor.
I suspect the capacitor is only there to reduce EMI. It may also help with brush/commutator life by reducing sparking.
As for changing from 3.6 to 7.2V, that will certainly improve the motor's torque/acceleration. But unless your motor is rated for the higher voltage, it will also burn out your brushes faster and may overheat the coil windings enough to melt things.
Honestly I didn't think about weight - I started with motors , transistors , heat sinks , a littler motor for the steering parts , more streamlined shaped . But removing weight is achieved by removing the main part from the chassis which has negative effects on the streamlinedness (that is a new word XD ) . The only thing I can remove is a little plastic part from the inside which covers the radio board . As well as some screws which hold the gearbox on the chassis (unnecessary - the gearbox still wouldn't come out even after I tried)
Larger wheel diameter can be achieved but It wasn't far from impossible to take those wheels out (I wanted to take the gearbox out which required the wheels to get out , where I failed) and I'm not sure what wheel would be suitable .
The motors are perhaps one of those simple 1.5 v or maybe 3v ones , which do withstand higher voltages (I've attached a 1.5v to 9v battery and it didn't burn . I gave 12v 500mAh to an LED and it didn't burn (not related but interesting)) and now they'd receive 3.1 v each .
Well the difference made by capacitors wasn't tested on these motors . I gave a 12v motor 9v . Then I soldered a UVC (unidentify valued capacitor) to it , it seemingly did make a difference . And as you mentioned , it took a little bit time to turn on and it made it spin a bit faster-more powerful . I'd prefer to do the test on some other motor , because I don't like to solder a capacitor - de solder and repeat - what other way there might be to test it ?
And thanks everyone ! 
You attached what kind of 9V battery to the motors? The square PP3 "transistor" battery is able to source hardly any current, it's output voltage drops significantly when any kind of load is placed on it. You might get 3 volts out of it, if you're lucky.
Again, as for your LED experiment, what power source were you using? Battery? Wall wart? Some LEDs are rated for 1A of forward current, so if you supply it with a weak alkaline battery or a current-limited power supply, you may not have exceeded the spec and that's why it didn't burn.
In your experiments, you need two multimeters. One to monitor voltage and one to monitor current. Otherwise, you have no idea what you're doing.
As for swapping capacitors, solder in a 2-pin female header, for example:
Then you can plug and unplug the capacitors.
Intuitively, it seems quite logical the capacitor thing. Starting a motor is where you need the most current. The internal resistance of your battery might limit said current, hence the use for a capacitor able to give a short boost at startup.
Bianco, a capacitor may help with the current surge when starting a stopped motor. But only if placed across the battery terminals, not the motor terminals.
Also, a very large capacitor (dozens or hundreds) of microFarads will likely be required to make a noticeable difference.
BTW, LiPo batteries can source a LOT of current, so I don't think they need any help. The surge cap concept may help when using crappy chemistries, like alkaline.
tylernt:
Bianco, a capacitor may help with the current surge when starting a stopped motor. But only if placed across the battery terminals, not the motor terminals.
That's a really good argument.
BTW, LiPo batteries can source a LOT of current, so I don't think they need any help. The surge cap concept may help when using crappy chemistries, like alkaline.
Alright but still, it depends on the cells.
Worth a try... run some time trials and let us know.
The car uses some of those "rechargeable weird batteries" (the ones with some plastic covering them and a socket comes out) which takes 4-6 hours to charge . But this new battery takes 8-12h to charge so it does make a difference .
The LED experiment was done with a regulated , 0.5 Amps 12V AC to DC converter . Just wanted to find out the + and - of it so I wouldn't burn my actual circuit . I didn't know what a multimeter was capable of and I didn't know where ours WAS . So I had to do this 
And thanks for the pin header idea . I have a 40x pin header - the problem is , I have no Idea how to cut it into pieces . Male ones are easier , maybe I'd put male pin headers then use female-female jumper wires (which I don't have) .
It sounds like you have either a LiPo (if it's rectangular) or NiCd/NiMH (if you can see cylindrical shapes inside) battery pack. Those chemistries are capable of delivering several amps, so I don't think a capacitor across the battery terminals is going to make any measurable improvement.
Yes , there are 3 cylinders . However it did have capacitors itself (from the beginning)
Arman5592:
Yes , there are 3 cylinders . However it did have capacitors itself (from the beginning)
That's interesting. I've seen many NiCd packs and never seen a cap in one. There's sometimes a thermistor, though. I'd be curious to see a pic.
The capacitors are on the motor . I did however "add" a little board of my own to the car , which I'd like to call "extra options board"
I placed pin headers for the capacitor (cut off the capacitor) , but I did consider about leaving some space , so later I'd attach to Arduino and make it an awesome robot (really , making a radio controlled robot is pretty hard and costly) .