WHAT PSU CAPACITORS SHOULD I USE ?

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exxos
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WHAT PSU CAPACITORS SHOULD I USE ?

Post by exxos » Fri Aug 18, 2017 8:26 pm

This is a question I get asked almost daily...

Before I explain some things, please considering buy the capacitors kits from my webstore if I sell a suitable kit. I have spent a great deal of time & money over the past 5 years alone, working and diagnosing PSU issues and finding solutions. While I may make a small profit on the capacitors I sell, this is considered as a donation to myself for all the work I have done. It really isn't fair on myself to spend a lot of time helping people find capacitors for their SR98 etc just to save a few ££'s on the parts which I already sell.

I do not document (and don't really keep) part numbers for myself or my website in general anymore. Simply due to every time I research 100's of capacitors, 6 months later they are no longer stocked, or discontinued. I have had to change the rectifiers in my kits several times due to them becoming obsolete in one respect or another. Updating my site with constantly changing parts would turn into a full time job, and I just don't have the time to keep on top of it. Normally I bulk buy capacitors in 200-500 packs because of this.

Of course I do not sell everything so here is what you have to do..

Generally I recommend the Panasonic FR series for all the general values. Often around 1,000-4,700uF. They are good ESR values and I personally use them on my own built PSU's.

Much higher uF values, I tend to look towards EPCOS. I use 10,000uF EPOCS in my PSU's as they are a good price and offer better ESR ratings then most other brands, including Panasonic. Of course there is no use paying £10 for a capacitor if a £3 one is similar or better rating from another manufacture. So it isn't "cast in stone" that I only use FR series for everything, because I don't.

Similar with the higher voltage capacitors, Once one is found with the physical dimensions, there often isn't much choice left. Generally the ESR values for high voltage caps isn't great anyway. Though each datasheet has to be looked at to see which is the best.

Often choosing one capacitor can take a few hours of work. So if anyone wants to find their own capacitors then heres what to do...

First of all, if we need a 4,700uf capacitor then do a search on a site like farnell. Select the value, dimensions, voltage rating, pin pitch from the parametrics table. Click search and you will probably have around 200 results.

The un-educated people (sorry!) will often just go for the cheapest one which will fit. But that is a pretty dumb thing to do. While in general capacitors are good, there are some I have seen which are so bad, they are likely worse than the 30 year old caps in the PSU already! I really do not understand why such bad caps are on the market , but they are. Sometimes they are not so cheap either!

Take a look at the datasheets. Look for ESR / ripple current/amps/ohms . If the manufacture doesn't list this information. Then that manufacture is either stupid, or their capacitors are not worth buying. In which case, avoid whatever series of capacitor and brand you are looking at.

Take the Panasonic FR for example...EEUFR1C472

It is worth noting that the physical dimensions of the capacitor also affect its ESR ratings. It is not totally dependant on its value or voltage!
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Highlighted below is the same value and voltage capacitor, but note one is a "L" version. L=Long version where it will be slightly taller than the non-L version.
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We can see the L version is 35mm high and 12.5mm wide, offering 3750mA.
The non-L version is 25mm high, 16mm wide, offering 3820mA.

It is important to make sure you order the physically correct dimensions to fit the space you have. If you have a little space to fit a wider or taller capacitors, and its a better spec, then I would be included to use it. Though in my example above the difference isn't huge, but on some capacitor values it can be. If there is a better spec part and its only a fraction more expensive, then I would buy it. If its double the price or more for
a small gain in spec, then I probably wouldn't go with it. Though this is based on myself having to order 200+ capacitors so I have to keep my outlay costs reasonable.

A example of a similar capacitor by Multicomp..
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We have 1960mA, whereas the Panasonic was almost double that. Of course the Panasonic is about 20pence more expensive (about 40p Multicomp, 60p Panasonic) . Both capacitors would work fine in this example. Though I will always go for the higher spec parts. If I am going to the trouble of changing parts, I want to fit the best ones I can find.

These are just some example of what to look for with choosing capacitors. Its also why I am reluctant to get involved with deep conversations about choosing capacitors simple because looking through 100's of datasheets (per capacitor!) can take several hours and I don't have time to look through them all to "suggest" a capacitor to everyone, sorry!

I will say its not that difficult to look through the datasheets. Just avoid capacitors ranges which do not list any proper ratings. Often while Panasonic (maybe even rubycon, epcos etc) are pushing towards 4,000mA on the 4,7000 value, manufactures who do not list the proper ratings, do so for a reason, normally because they suck! A few years ago when I started this research there was capacitors on the market which were around 200mA! That is pretty dire indeed. Though these capacitors are still out there!

Only buy capacitors from reputable suppliers such as farnell, mouser etc. Don't go looking on iffy auction sites for the best deals on capacitors. Just no way to know if they are genuine or a China Knock-off. Don't assume the supplier has the correct specs for the parts they are selling either, as often they don't!

I hope this will give some insight to helping people chose capacitors. Though as said before, please considering buy parts from my store. Its not fair on myself to go through all this work for people just to buy parts elsewhere.
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