Low ESR Capacitors Suggestion

Electric Motors and Controllers
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ilithis   1 µW

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Low ESR Capacitors Suggestion

Post by ilithis » Jan 15 2020 5:16pm

I'm in the middle of making some upgrades to my ebike controller and I'm having a hard time finding a low ESR capacitor that will fit my needs and was wondering if anyone had any suggestions.

The mystery cap in question needs to be:
100V+
470uF
18mm in diameter or less
25mm in height or less

The only capacitor I could find that comes close is the Panasonic EEU-FS2A391. However, the largest capacitance available is only 390uF. I'm not sure if that is a small enough difference to matter since the current caps in my controller are rated at 63V 470uF. Does the capacitance rating matter for the capacitors between the P- and P+ of the controller?

Thanks for reading!

-Ilithis

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spinningmagnets   100 GW

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Re: Low ESR Capacitors Suggestion

Post by spinningmagnets » Jan 15 2020 5:30pm

If you are suppressing voltage ripple, the resistance needs to be as low as possible, but the capacitance can be very small. Of course if you find a capacitor that will work, and that capacitor is large, that will not hurt anything.

viewtopic.php?f=3&t=104226

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amberwolf   100 GW

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Re: Low ESR Capacitors Suggestion

Post by amberwolf » Jan 15 2020 6:28pm

also, you can parallel capacitors of a smaller size to equate to a single larger capacitance, as long as there is room for them in there.

billvon   1 GW

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Re: Low ESR Capacitors Suggestion

Post by billvon » Jan 15 2020 7:00pm

ilithis wrote:
Jan 15 2020 5:16pm
I'm in the middle of making some upgrades to my ebike controller and I'm having a hard time finding a low ESR capacitor that will fit my needs and was wondering if anyone had any suggestions.
Let's back up. Why do you need a low ESR cap? EMI filtering? There are better ways of doing that. LF ripple reduction? That is often not as important as people think it is. HF ripple reduction? Smaller values work better for that. Preventing voltage dip when you accelerate? No way any reasonable cap will help there.

In addition, decide what frequency you want to rate the ESR at, because caps are rated for different frequencies. The two most common are 120Hz (for AC supplies) and 10KHz (for switchmode applications.)
The mystery cap in question needs to be:
100V+
470uF
18mm in diameter or less
25mm in height or less

The only capacitor I could find that comes close is the Panasonic EEU-FS2A391.
These caps should all meet those requirements:

EKZE101ELL471MM25S Chemi-con
SMG100VB471M16X25LL Chemi-con
UFW2A471MHD Nichicon
--bill von

ilithis   1 µW

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Re: Low ESR Capacitors Suggestion

Post by ilithis » Jan 15 2020 9:55pm

I was looking at other threads here on endless sphere and came to the conclusion that low ESR caps are desirable. I figured since I wanted to upgrade to be able to use a 72V battery, that I might as well get decent capacitors as replacements instead of just any capacitor.

An example of what I was looking at:
viewtopic.php?t=102053

Which I guess poses the question, do I really need a low ESR capacitor or would any 100V 470uF capacitor do?

I'm not sure about the frequency at which my controller runs at.

Thanks for your suggestions, I'll give them a look.

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amberwolf   100 GW

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Re: Low ESR Capacitors Suggestion

Post by amberwolf » Jan 15 2020 10:46pm

the good news is that a low esr cap from a name brand like panasonic, etc., is likely to be a much better cap, and last longer under the conditions inside a controller, than a random generic cap. ;)

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