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Originally Posted by Diceman83
thanks sr... that's about what I was thinking, just didn't know for sure.
Just a few more questions... What ferad levels are we talking about? How many amps can a 1 ferad cap hold? It would have to 15 to 25 amps to do what you're talking about, I would think.
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well it's not so simple....as the capacitor discharges its voltage drops, so the amount of current it can supply is a function of its current voltage, time, etc.
A 1 farad cap can supply 1 amp of current for 1 second before dropping by 1 volt. So if it was the only source of power (which isn't possible because there has to be something there to charge it, but this is just hypothetical), then it could supply 1 amp for 1 second before dropping from 14V down to 13V, or 2 amps for .5 seconds, or 4 amps for .25 seconds, etc. The amount of time it would need to supply current for would be in the milliseconds, so it could supply a LOT of current if the rest of the electrical system could back it up fast enough. In 10ms it could supply 100 amps and only drop by 1 volt, or 50 amps and only drop by .5 volts, etc. See why it's so hard to say how much current it can supply? It's almost impossible to say because it depends so much on how fast the alt and batt can react, how much current they can supply at 14V, 13V, etc (an alt can supply a LOT more current at 12.5V than at 14V).
And then you have the carbon caps out there which have such a high ESR that they're practically useless for this application....