capacitor specs

I think my search skills just fail me, so I appologize for a new thread on something that I'm sure has been covered.

What is the stock capacitor size on the MM? I crushed one on labor day landing poorly from over 15 feet in the air. My shock tower flexed forward and crushed the rear most cap on my MM. I work in an office that has a lab full of electrical engineers who will do the cap repair for me if I'm uncomfortable soldering it, and very well may have the correct cap needed in their little box-o-goodies.

My MM is working fine with the one crushed cap, but is heating up faster.

Thanks,


DickyT

[BrianG]

330uF and 25 or 35v (35v would be better if it physically fits). Make sure it's rated for 105*C and low-ESR type.

While you're at it, you outta see if they have a few extra of those caps and add some close to the ESC on the power wires...

[Arct1k]

ahh interesting thread - i've a couple of mm and also have some caps with now dented tops.

Functionality wise the esc seems to be running fine - have i likely killed a cap and how would i test it?

Thanks,

chris

Originally Posted by BrianG

330uF and 25 or 35v (35v would be better if it physically fits). Make sure it's rated for 105*C and low-ESR type.

While you're at it, you outta see if they have a few extra of those caps and add some close to the ESC on the power wires...

Perfect, thanks Brian!


Edit: Bah... I just dug through their toy chest and they have some with the correct ratings, but they are about 10x the size. Where is a good online place to order from, none of my local rat shacks carry electronic components anymore? I have checked 10 stores and they all told me to buy them online. And how many should I add on the power line close to the board?

I have read that anything more than two is a waste, but Frank at Quark said, the more the merrier.

[BrianG]

Denting/deforming a cap can reduce the voltage rating since the conducting plates have probably been squashed closer together. Dented bad enough could short the plates.

A cap with a rounded top means the electrolyte has expanded (from heat, overuse, etc) and is on its way out and should be replaced.

You are right, the more caps the merrier, but the more you add, the harder it is to stay neat while keeping the leads short enough. Plus, you get diminishing returns the more you add. For instance, if the ESC has two 330uF caps, that's 660uF total. Adding two more doubles the total capacitance to 1320uF - A pretty good gain. Adding two more increases it yet more to 1980uF, but obviously won't double the total value. However, the cap bundle is starting to get unwieldy and harder to connect close to the ESC.

No, you won't find these types at any RadioShack that I know of. As a matter of fact, if you ask them for low-ESR caps, they will simply give you the deer-in-the-headlights look and then try to sell you a cellphone. Seriously, larger parts suppliers like Mouser, Newark, etc has them I'm sure. You can sometimes find some on eBay as well.

[NovakTwo]

When Bob first dynoed the MM, he blew out all 3 caps immediately. He removed the caps and cleaned up the PCB---he said it wasn't particularly easy. Then he installed one of our trans-cap modules, and it works just fine.

[lincpimp]

Dynoed the MM? Any more info on how you guys at Novak test stuff. Since you are probably the larhest of the brushless eqip makers, you guys have most likely tried out all of the competition's stuff. Also what is a trans-cap module? Do you sell them seperately? Great to have a Novak rep here to ask questions.

[NovakTwo]

Here's a link to the trans cap module:

Novak Electronics GTB Racing Power Trans-Cap Module

And, here is a link to an article about capacitors w/photos:

NOVAK ELECTRONICS POWER CAPACITOR

[BrianG]

Ah, the trans cap contains voltage clamping transorbs. How much energy can the circuit safely shunt before heating up too much? Can you release specs on the transorb devices (or at least the device part number so I can look it up)? I wonder how it would perform if one were to upgrade the cap from the stock 10v 5600uF to something in the range of 35v ~1000uF (trying the keep the physical size close to the same).

Also, the cap is only rated for 10v, which limits the battery voltage to 2s or 7 cells max. Too bad there wasn't a higher voltage version, something in the 25v range for people with 3s to 5s systems.

[rchippie]

So would this trans cap help the MM at all, if so were would be the best place to connect it ?.

[BrianG]

Well, we know that better caps helps. The transorbs clamps the voltage at a preset value to shunt those high back-EMF spikes.

I see the part number as 540GEE, but all I can find is the datasheet for 540. The GEE must be manufacturer/date code. But the 540 part is meant for quite high voltage - in the 400v range from what I can see...

[bdebde]

Gee, I guess i will have to try some caps (hint, hint, Tony).

[BrianG]

BTW: NovakTwo, there is an error on this page: http://www.shopatron.com/product/par....56.7400.0.0.0

The title says 680mF, but the cap is actually 680uF. Just a factor of 1,000 different. Not a big deal, but someone might make an issue of it...

[wallot]

I use 470uF caps. Two did the job on my quark. Tried 4 but no difference, but keep them on.