...more on capacitors in cars


Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 4771
Registered: Dec-03
on a side note, it's not that I personally have a habit of blowing up electrolytics, but I have seen a few cars brought into the shop where some kid tried to wire one up, didn't RTFM, and did manage to get one to "vent" itself inside the car. trust me, it can be rather explosive due to the rate of depressurization and just the raw size of those caps.

But as annonymous noted in the prior thread, anything is dangerous when it's misused.

I see enough people short out amplifiers and head units by sloppy work, miswiring, not knowing what they're doing, etc. I hate to think of what happens when these people meet something that has more potential energy stored in it.
generally, 12 volt car electrical systems don't hurt folks.. much. The problem with that, is it leads to carelessness at times.

Unregistered guest
GlassWolf, do you charge them more when the wiring is burnt so bad you can no longer tell which color insulation belongs on which wire?

Yes, even sporks can kill in the wrong hands. I'm a big fan of DIY'ing but people ought to put the necessary effort into doing their homework, the info printed on the box isn't sufficient. If you don't know what ohm's law is, don't mess with stiffening caps, the real danger isn't the caps or the voltage or the current, it's the people, and always will be.

OOOk let's raise some hell. Who here thinks its all been said about stiffening caps and therefore this is a waste of space???

Good, close this page now, as for the rest..

What's the shelf life of these suckers, does any one brand stand over the rest in this respect? Or do they even tell you?

What else..

Let's say you find a deal on a brand new stiffening cap who's shelf life is near the end.. what do you do?

You can try re-forming it, but you better know what you're doing. I've heard of various ways of doing this, they all have one thing in common "limiting the current".

This is probably the real and true reason for manufacturers wanting you to precharge the caps before use, you're essentially re-forming them. I would still discharge it again before actually installing it though. Just so I dont' weld anything.


Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 4816
Registered: Dec-03
I haven't seen much on their shelf life, but most of them should last longer tahn the car.. haha

you remind me of a quote I heard once.. something like "if guns kills people, then can I blame my pencil for my spelling mistakes?" hahaha

the other reason for pre-charging a cap is to equalize the voltage differential between the battery and the capacitor when you connect it.
Mainly it just avoids sparking and such, which can be very bad since you're often pretty close to a gas tank and such in the trunks of cars.
As for shelf lives, I'd just toss out the cap and buy another. They're only about $50-100.
It's not like tossing out your $1500 head unit.
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