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Old 08-15-2007, 03:33 PM   #1
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Default Bigger capacitor for Nosram brushless ESC

Hi, I've a Nosram Matrix Evolution 2007 edition brushless ESC which already comes with a capacitor but my friend told me I can improve its performance even more by using a bigger capacitor.

My friend says that there is no harm or disadvantage but only benefits. Is that true? Would anyone be able to advice on this?

I know Nosram/LRP sells the upgrade kit that includes a bigger capacitor but I heard I can just get a better one from an electronics DIY store for a much lower price.

I know next to nothing about electronics so hope some of you electro-gurus can make recommendations. Thanks in advance
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Old 08-15-2007, 05:30 PM   #2
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I'd be interested to hear the responses to this. My understanding is that the capacitor stores power when connected to the battery. The capacitor can discharge faster than nimh packs and so in cases of immediate power needs (ie zero to full throttle), the capacitor can deliver a quick burst of power faster than the battery pack.

If that's true, then a bigger (larger) capacitor would be able to store more power (ie deliver the power for longer). But you only really need power from the capacitor for as long as it takes for the battery pack to catch up.

This means there's definitely a point where you're gaining no benefit from going larger. I would have assumed that the manufacturers would try to supply something between the ideal, and what is practical in terms of size. I also know that since we're in the offroad forum, this initial 'punch' is probably not as critical as it is in on-road, which these upgrade kits are most likely designed for.

So personally, I reckon you'd be hard pressed to feel a difference by going larger. If you did though, definitely go the electronics shop and not manufacturer. You'll pay about 1/10th the price.
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Old 08-15-2007, 10:06 PM   #3
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Quote:
Originally Posted by Lplate View Post
Hi, I've a Nosram Matrix Evolution 2007 edition brushless ESC which already comes with a capacitor but my friend told me I can improve its performance even more by using a bigger capacitor.

My friend says that there is no harm or disadvantage but only benefits. Is that true? Would anyone be able to advice on this?

I know Nosram/LRP sells the upgrade kit that includes a bigger capacitor but I heard I can just get a better one from an electronics DIY store for a much lower price.

I know next to nothing about electronics so hope some of you electro-gurus can make recommendations. Thanks in advance
Yes and no.. man thats a can of worms to open up.. Let me try and sum this up with a short answer.

The caps used inline with the power supply to your ESC are mainly used to 'stiffen' the supply voltage. Had they not been implimented the inrush of current to the ESC would cause a voltage drop that can cause anything from glitching to tripping the LVC circuit (for lipo cutoff) and may even drop it enough to cause the PWN signal to the FET's to lose strength resulting in a chaotic surging. It's really there out of design necessity.

You could increase it, but there are several factors to consider that I won't get into simply because I don't believe you will gain anything from it unless for some reason you are experiencing some of the things I mentioned above. The capacitors are selected to compliment the capabilities of the system and should it not be doing it's job properly, you are most likely pushing the envelope of the equipment

Although choosing a proper high frequency / high temp cap to further stiffen the supply voltage has *some* outright benefit to keeping voltage in check and providing a very momentary but powerful discharge, is it worth it to give up the space? Choosing the 'proper' cap for the job would result in a nationwide search for the space to mount it!

Not to mention you have no idea how much inrush current your ESC is capable of. If burst current is mentioned in the specs thats a good figure to start with. If not you may actually damage your ESC by having that much current on tap. A battery has a discharge rate, but a good cap will always have a far greater discharge value. And thats assuming you choose a cap large enough to actually yield some results and assuming you found the room for it (a couple thousand microfards in a high temp/high freq cap is not exactly small). And then there is the math....

But now I'm getting carried away and rambling.. I just don't think it's worth the headache. I know it seems like a simple mod, but it's not. Not if you want it done right and for the right reasons. Hell I just brushed up on a 16 page whitepaper on simple fuse technology. Electronics is not as simple as it seems. I learn new things every day and I've been doing this for well over a decade.

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Old 08-15-2007, 10:47 PM   #4
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I guess its safe to say I dont know enough to mess around with such things. Heheh.

Ok, I'll not be greedy and just focus on my driving technique instead.
But boy am I glad I asked. Your answers have been most interesting and educational for me. Thanks guys!
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