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Novak Power Capacitor

Novak Power Capacitor

Old 12-10-2003, 06:03 PM
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Default Novak Power Capacitor

Does anyone know the value of the capacitor for the Novak Atom. I can't seem to find the one that came with it. If I know the values, I could buy one from Radio Shack.

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Old 12-10-2003, 06:11 PM
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I know the one on the GT7 is 10v 4700uf. NOVAK claims you have to buy it from them. Radio Shack doesn't carry those in radial lead or axial lead.

However I have found a guy on eBay that sells the EXACT one that's on the GT7.
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Old 12-10-2003, 06:21 PM
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are there any on ebay now? I can't find any that would work for rc.
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Old 12-10-2003, 06:27 PM
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kinda on the subject, i took apart a old cb radio, and found many capacitors. could i use these not for the easy, but for the extra power supply for radio and servos??
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Old 12-10-2003, 06:30 PM
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Just do a search on eBay for "4700uf" and see what you get. That's how I found it.

I am also going to test out a 10000uf and see if that will work "twice" as good as the 4700
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Old 12-10-2003, 08:26 PM
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I know I have bought one from Radio Shack before, but didn't remember which one.

Thanks for the information.

Jon
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Old 12-10-2003, 08:36 PM
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is it true that the higher the voltage the less punch?
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Old 12-11-2003, 02:45 AM
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is it true that the higher the voltage the less punch?
I am no electrical genius but I think you want to keep the voltage rating as close to what enviorment you are operating in. For example, a 10V cap on a system that runs 7.2 volt, a 16v cap for a 12v system etc.

The uf rating is the capacity of the cap. The larger the capacity, the longer it takes to charge the cap (which I think is true for the voltage aspect as well) between discharges. All the manufacturers like NOVAK claim that the 4700uf cap is perfect for our RC stuff, I have read where some guys run 10,000uf and in an extreme case of experimenting I have seen photos of a guy with a 25,000uf cap that was like 4 inches long!

I am going to try the 10,000uf cap when I test a 6 turn motor I bought just to see if it will work. I will also test the 10,000 cap on my standard 19T as well.
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Old 12-11-2003, 03:20 AM
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You can use any 16V 10000uF.
They work just fine. Just a tad bigger than the 16V 4700uF but it gives more (if you can measure it) punch.
No problem at all with 16V instead of 10V.
Buy the 105șC rated ones.
Don't miss polarity.
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Old 12-11-2003, 03:28 AM
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I study electronics, so here's my opinion:

Function: When your pull full throttle, especially when your car stands still, your motor will draw maximum amp's. This might cause that the battery can't keep the voltage up, especially with hot modified motors. The capacitor acts as a buffer, it will help the battery to keep the voltage up, so your radio equiptment will receive the power it needs to keep operating normally, therein reducing glitching. Furthermore, your motor will have more punch out of a corner.

Voltage: choose the capacitor with the voltage as close as possible to voltage you will use. In most cases you'll wind up with a 10 or 16volt capacitor for 6cell use. A higher voltage means a thicker capacitor.

Capacity: choose capacity according to your needs and motor. I run 12turn eurospec mod, and I use 4700uF. A less powerfull motor will require less capacity, there is a point where more capacity doesn't help. Also, the more capacity the larger the capacitor, so keep weight and available space in mind.

Connection: the capacitor has a long and a short lead. The short one goes the minus, the long one to the plus (of the battery). If you foul this up, your capacitor will selfdestruct. That will leave an awfull smell, and a lot of mess (seen it). Also, there's a minus marking on the housing of the capacitor, if you've already cut the leads, or are uncertain.

Only capacitors from the manufacturer: Nonsense, I used an old 40volt 4700uF capacitor the entire last season with good results. It's just a selling trick.

Hope this will help.
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Old 12-11-2003, 02:45 PM
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thanx for the help!!!

u rock!
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Old 12-11-2003, 03:10 PM
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Thanks for the information guys.

Jon
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Old 12-11-2003, 03:14 PM
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Wow again? I got an email requesting some clarification to this link so here you go.

Power caps explained. Again. (Futureal keep this posted someplace maybe the tech section)

This may sound Like a Novak Add or something, but that is were my experience is. The statements apply to most ESCs.

The power cap on a Novak ESC is there to prevent the ripple current that is created by the ESC from damaging itself. It's not really for any full throttle response, as when the ESC is at full throttle, it is not switching, it turns into a "junction" only. It would be like soldering the wires directly from the battery to the motor. Full power is full power is full power.

The Power cap is actually there for partial throttle operation. When you are using anything other than full throttle the ESC is switching very fast. A Novak ESC switches faster than most (not the drive freqeuncy, but the switching used to create that drive frequency) so the problem is more severe. Due to the high rate of the switch process a ripple current is created. This means the voltage is flowing into the fets so hard and fast, that when the ESC switches to off, the current continues to flow and heats up the parts. This is probably an over-simplified explanation, but you get the idea right? So the Power Cap absorbs the ripple current, prevents the heating of the ESC and feeds the stored voltage back to the motor on the off cycle. That inturn creates a much cooler ESC and vastly improved mid range throttle response.

You can easily test this, but running your motor at partial throttle, then removing the power cap, the motor will slow down, when you reconnect the power cap the motor revs up a little.

Power caps are not for full throttle acceleration, I can see why that mistake is often made, it makes a little sense, but is not correct. They may have an effect on it, but are not there for that reason.

After that people want to know why you have to use a special Cap. Reason for that is that the capacitor has to be the correct "performance". If the cap is the wrong ESR value it will not do anything in the system, so it doesn't provide any protection. Problem is capacitors don't spec the ESR, it is usually indicated by the manufacture in a "series" or line of parts. The Radio Shack cap will damage your ESC.

Next question is usually about schottky diodes.

A schottky diodes is an electronic one way valve for voltage. When your motor free spins it creates voltage that is fed into the ESC. A schottky prevents that voltage from getting to the ESC. As a side effect you get more consistant breaking. They are still required even if you don't use the brakes, becuase the are stopping damage that happens every single time you lift off the throttle. Schottky diodes also increas motor voltage in a similar manor to power caps. My understanding of that isn't as clear, but similar RPM gains are noticed.

Currently Novak has been developing our ESC dyno. We have been working on ESC comparisons and what does what. What we have found for sure, is the problem does not come from the ESC or what it's doing, motors from only a couple years ago are more efficient and create much smaller issues. Today's motors may seem great, but the truth is they are less efficient overall. There are always acceptions so don't jump on me if I've said something you don't agree with or have different experience.

Anyfurther questions directly to me, please shoot me an email.

Thanks
Charlie
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Old 12-11-2003, 08:43 PM
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Yeahh yeahhh. We hear ya Charlie

Nice post bro.
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Old 12-11-2003, 08:46 PM
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Originally posted by RBLove
Yeahh yeahhh. We hear ya Charlie

Nice post bro.
i agree
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