Capacitor specs?

[antnee]

I need to get a new capacitor for my Xceleron ESC (1/10th scale), nipped into maplins today and theres loads!

What specs should I be going for?(Voltage, capacitence, etc) Also what 'type' should I get?

[westie]

I use 16v 4300uf

[MikePimlott]

Aluminium Electrolytic Radial 85 or 100 degrees

across the Lipo 16V anything from 2200uf to 4700uf (the more microfarads the bigger the case size, check dimensions.

Across the BEC 10V will be ok.

[adon30]

Most systems use the radial electrolytic caps.

The voltage rating needs to exceed the max votage that it is going to see and the capacitance needs to be large enough for any spiked/ demands.

Westie has recommended a 16V rated one with a capacitance of 4300uF

I have also seen 25V rated 2200uF capacitors recommended.

16V+ will be fine.

Ripple current capability will also be important. I have seen blown capacitors on PWM systems before due to an inadequate ripple current rating of the capacitor. This was none RC car related though I hasten to add.

This is what Hobbywing recommend as their 'super' capacitors
http://www.hobbywing.com/english/Art...?ArticleID=417
Basically 16V 1320uF with high ripple capability.

Hope this information helps some what......

[adon30]

To add to Mikes.
A 16V 4300 uF will be a different size to a 25V 4300uF, so check the dimensions so you don't end up with something as big as the car!! For example a 400V 4300uF would be about 15cm long!

[antnee]

Should either of these be ok?

222uF 16v

4700uF 16v

[coolcars782]

According to Novak there power trans cap (Here) for the gtb will work with any brushed/brushless speed controlled (expect high voltage esc's) and that is only a 5600uF 10V one.......

[SlowOne]

In my experience one should use the ones recommended by the speedo manufacturer. It's the high ripple capacity - the speed with which they can switch - that's most important, as Adon says. Most, if not all, the ones in places like Maplin are not good in this respect, they just have the same numbers as the originals.

I appreciate that there are cheaper alternatives to the manufacturer's prices, but in this case, as in so many others, you get what you pay for. A low switching speed makes the speedo hotter and can lead to other issues with speedo performance. If you trawl the 'net for the exact equivalent of the Tekin/HW capacitors, it is difficult to get them for much less than the manufacturer charges. If you find a cheap one with the same numbers, it is probably not the same specification as the original, and will therefore not perform as well. HTH

[MattW]

Agreed with Slowone - it is quite unusual to be able to get the correct ones much cheaper. This seems even more the case now that many of the manufactures have switched to the multiple caps on a circuit board idea, and it's also often the case that there are other components on those boards as well.

If you do decide to use a 20pence cap, then I wish you well - I don't fancy your chances.

[adon30]

You could try farnell or rs but I doubt they will have much suitable. The only other thing would be to try and wrangle some 'samples' from a supplier.

I remember with the application at my old company we had to go up a voltage level to get a better ripple current rating but this doubled the size of the thing.

As both say above check what the manufacturer of the speedo recommends and see if you can find the same part. Electronics parts are very hard to get hold of at the moment due to a lot of the far east manufacturing facilities closing during the current recession. Just ask anyone in automotive electronics.

[Northy]

Capacitors don't "switch"

You'd find the ones that the speedo manufacturers use in RS and Farnell if you knew what you were looking for, but I do agree, not for 20p

[damselfly]

Originally Posted by Northy

Capacitors don't "switch"

You'd find the ones that the speedo manufacturers use in RS and Farnell if you knew what you were looking for, but I do agree, not for 20p

Spot on.
Capacitors are just used for decoupling/surges in these instances.

[SlowOne]

Northy, Damselfly, sorry, wrong word. I think I mean the speed with which they can charge/discharge so they do take the surges that occur across the +/- terminals?