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        Discussion Adding Capacitors, what voltage and how much is too much?

#1 aerosoardude Jul 12, 2012 04:47 AM

Adding Capacitors, what voltage and how much is too much?
Hey all,

I've recently bought the 150A 6s ESC from HK. I'm not actually planning to use it in an rc car, but that's besides the point of this post. Bottom line is that I need to reduce the voltage spikes as much as possible.

I've been reading up on the topic of adding caps to escs. Every time someone adds capacitors, they seem to use ones that are nearly twice the input voltage.

The HK esc only uses 25V caps, good brand caps, but only 25 nonetheless.

My questions are:

Shouldn't I upgrade the caps to 50V versions?
And as long as I'm at it, how big of a capacity can I add?

Thanks for any and all help!

#2 wparsons Jul 12, 2012 07:34 AM

You can add pretty much as much as you want within reason (ie not adding 5000mah of capacitors). If you add too much you can damage the batteries when they try to charge up the capacitors when you first plug the battery in.

There's no benefit to running a higher voltage, unless you can't find the lower voltage ones easily.

#3 traxx de maxx Jul 12, 2012 10:03 AM

I think when adding caps to anything you need to go up atleast 30% more Volts than the system.
I think it's 30% but i could be wrong.

#4 wparsons Jul 12, 2012 04:46 PM

You don't *NEED* to add buffer in the voltage, as long as the caps are rated for the maximum voltage you'll ever run.

I would go with a bit more than 25v if you plan to run 6s since 6s fully charged is 25.2v.

#5 aerosoardude Jul 13, 2012 05:22 PM

I ended up buying 50v caps in case of voltage spikes. Don't mean to ignore your advice wparsons, but if larger won't hurt, then I might as well use bigger ones.

Thanks for everything!

#6 wparsons Jul 15, 2012 04:56 PM

^^ Like I said, there's absolutely no harm in having higher voltage ones. You won't see any benefit if your voltage is well below the limit of both, but if you're running right near the limit it'll be nice to have the extra head room just in case.

#7 traxx de maxx Jul 16, 2012 12:03 PM

do they not store the same amount of voltage that supplies them anyway.
so if you use it on a 20V system then only 20V will be stored no matter how high the voltage rating is on the cap, or am i wrong somewhere.

#8 wparsons Jul 16, 2012 08:48 PM

No, you're 100% right. They only store the voltage being supplied, the voltage rating is just the amount of voltage they can happily store.

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