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Installing a "raw" electronic component

Redoing my electrical installation (it had never impressed me) I need to install a largish elco (10000 uF, 25V) in an installation all done with crimp-on "Flachschieber" and fork or eye connectors.

How to attach such connectors to my elco? Or what is an alternative of wiring it? Trying to avoid soldering, but not fanatically.

I already realised that, however I do it, I must make sure the electrical connections do not carry any weight as they do on pcb's - the part will be tie-wrapped to the firewall.

EBZH Kiewit, Belgium

Use a capacitor with screw terminals and then use ring crimps.

A bit like this

http://uk.rs-online.com/web/p/aluminium-capacitors/3819015/

Darley Moor, Gamston (UK)

Hm. I could have thought of that myself - but I thought only the largest elco's are available in that "screw terminal" style? Then again, one day I may well have the same issue for a LED or a power resistor.

EBZH Kiewit, Belgium

BTW you can install a larger value capacitor, and certainly a larger voltage rating capacitor, in this position.

The capacitor probably just sits across the battery bus and the value is not critical. Anyway, electrolytics have a crap tolerance - say +80% -20%. Going for a higher voltage rating (to get the desired can style) improves reliability dramatically.

Administrator
Shoreham EGKA, United Kingdom

Going for a higher voltage rating (to get the desired can style) improves reliability dramatically.

You seem to disagree here with most others.

There seem to be two schools:

  1. any voltage below the rated voltage has no effect on aging

  2. voltages much lower than rated increase aging

http://electronics.stackexchange.com/questions/17048/does-the-voltage-across-an-electrolytic-cap-significantly-alter-its-lifespan

It's probably more important that you make sure ripple currents are within the rated limit.

LSZK, Switzerland

That may be true for wet electrolyte caps i.e. they need the voltage to maintain the oxide layer in a good condition, but would you use one of those in a high reliability application? I would use a solid aluminium cap.

But you may be right that all the ones big enough for this application (the large screw terminal style) are wet electrolyte - example. I did only a quick google.

The solid ones are in smaller cases. All the ones we use at work are solid aluminium, or tantalum.

With tantalum caps, there is a dramatic life increase by going for a higher rated voltage.

Administrator
Shoreham EGKA, United Kingdom

In this particular case, the elco is there so that the rectifier/regulator sees something that behaves slightly like a battery even when the battery isn't there, for instance when the charge fuse is blown.

So in normal circumstances there are no ripple currents at all, except for the elco's impedance being lower than the battery's, or so I should think. Come to think of it, I could do worse things than to parallel it with a faster smaller capacitor.

EBZH Kiewit, Belgium

It's an interesting question, what the ripple current might become should the battery become disconnected, or dry, etc.

One could probably have a good stab at the value, knowing the amplitude of a 3 phase rectified 24V alternator output, and taking max engine RPM as the worst case.

Here you go

I will leave it to Tom here to interpret the maths

Administrator
Shoreham EGKA, United Kingdom

You really believe we sport three-phase alternators in a microlight? Ever wondered the weight? Can't find the exact details now, but certainly the Rotax delivers a single phase AC, of up to 22 volts if memory serves.

EBZH Kiewit, Belgium
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