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<blockquote data-quote="helotaxi" data-source="post: 7095786" data-attributes="member: 550915">Still not technically correct...once the cap is initially charged it merely floats along with whatever the system voltage is.&nbsp; It doesn&#039;t draw any extra to speak of at that point.&nbsp; Unlike a battery that can supply a relatively large amount of energy before its voltage drops appreciably, a cap&#039;s voltage will drop at a constant rate as energy is drawn from it.&nbsp; Technically, once charged to system voltage, a cap is always charged fully.Some things to think about.&nbsp; The vast majority of the energy stored in a cap is not usable, ever.&nbsp; It might soften the initial voltage drop from the alt being overloaded or give the alt the mili-seconds that it needs to overcome its own inductance and increase output during a transient but as far as providing a real storage capacity for system use, even the biggest caps are useless.&nbsp; A cap with zero ESR (the perfect cap) has a usable storage capacity of 0.5 amp-seconds per Farad.&nbsp; Even small batteries measure their storage capacity in amp-hours.&nbsp; You would have to completely fill your car with caps to begin to rival the storage of even a small battery.&nbsp; Also because caps do have an ESR, the more current you try to draw from one, the more voltage is lost as heat.&nbsp; In a high current demand situation, a cap can be rendered completely unable to deliver any current because its output voltage is dropped to system voltage by resistance losses.</blockquote>

[QUOTE="helotaxi, post: 7095786, member: 550915"] Still not technically correct...once the cap is initially charged it merely floats along with whatever the system voltage is. It doesn't draw any extra to speak of at that point. Unlike a battery that can supply a relatively large amount of energy before its voltage drops appreciably, a cap's voltage will drop at a constant rate as energy is drawn from it. Technically, once charged to system voltage, a cap is always charged fully. Some things to think about. The vast majority of the energy stored in a cap is not usable, ever. It might soften the initial voltage drop from the alt being overloaded or give the alt the mili-seconds that it needs to overcome its own inductance and increase output during a transient but as far as providing a real storage capacity for system use, even the biggest caps are useless. A cap with zero ESR (the perfect cap) has a usable storage capacity of 0.5 amp-seconds per Farad. Even small batteries measure their storage capacity in amp-hours. You would have to completely fill your car with caps to begin to rival the storage of even a small battery. Also because caps do have an ESR, the more current you try to draw from one, the more voltage is lost as heat. In a high current demand situation, a cap can be rendered completely unable to deliver any current because its output voltage is dropped to system voltage by resistance losses. [/QUOTE]

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